Computer Ka Chota Answer

C programming

2012-10-09T00:11:00.000-07:00

Introduction

Before explaining C programming let us discuss what programming is ?????

well programming is the set of instruction given to the computer , instruction to get our job done .

In our daily day-to-day life we also give instruction to others like “bring me that” “complete the work” ,”go there” and etc .

So in computer science also we give instruction to the computer to get our job done like adding a bunch of numbers , finding solution to a mathematical problem , or doing some computational problem and so on

Like in English we follow grammar to complete our instruction like that we have specific way of giving instruction to the computer , and as in our real life we have many languages to communicate similarly we have many languages we can use to write these computer instruction called programming languages and the instructions are called programs .

So that was a loose definition of programming language and programs

In the list of many programming language C is one of the oldest and popular programming language , it is small but can produce many complex programs and if you are interested in the history of C programming please visit this link wikipedia C programming language

I won’t be describing a lot of detail on the theory part but still some information about C Language that I think you people should know

C Language is a procedural language that means it follows procedures or functions or sub routine in order to complete the task .
Well if you don’t know what a function is then not to worry you would know later in the course but for now function can be defined as self contained unit of code

C Language is a multi platform language that means you can develop programs for almost all the major platform with C like windows , Linux , Unix etc , you just need a compiler and in case if you wonder what a compiler is , well I am going to explain it just wait for a moment

So that will be enough about the theory part , Now

What is the programming process?

The programming process follows like this

So first we have the source code that is the code we have written in C Language , we then compile the source code with a compiler , So compiler is a program that converts a user readable program to something that can be understood by a computer and after that we get a exe file or executable file and then we run or execute the program

If the program executes well then its working fine but if not then it has a bug in it , a bug can be defined as a behavior of a program that we are not expecting , So in order to solve the problem we have to debug it , it’s the fancy way of saying “What Is Wrong In The Program”

We can start writing code in a command prompt which I find boring sometime so we would use a IDE or what’s called as Integrated Development Environment , it’s a piece of software that we use to write our program and for this purpose I am using DEV C++ , its free and easy to install and use , you can download it from the following link Download

I hope you have downloaded it and install it

So to create a new program just do

File < New < Source File or just type ctrl + n (for new document)

Now we can write our program here

Let’s write our first program

main()

{

printf("Hello World \n");

getch();

}

That is it , now give a name to the program like “hello” with an extension dot c , so that will be “hello.c” and change the “save as type” dialog box to “c source file” and save the file

You can compile the program from going to the menu and

execute < compile (ctrl +F9)

and run the program by

execute < run (ctrl + F10)

The output of the program is to display “Hello World” message on the

console like

Now let’s examine the program

main() { } - this called the main function , every c program should have a main function otherwise it won’t compile , at this point it might be difficult to understand what a function is but later it would be clear to you as we proceeds further but for now main is a function ,

every function has starting and closing round brackets following the function name and also opening and closing curly brackets which define the body of that function . Main is not the only function , there many more functions in C

function name ( )

{

Body of the function

}

Printf(“ “); - well again this is also a function , and we do not see a body here don’t worry you will know about it later in the course but for now it’s a C function that accepts everything that is inside the double quotes and display it on the screen , that is the function of this function

printf(“ display this message on screen \n“);

The semicolon – the semicolon is used to signify that “this is the ending of this statement” it’s like the “full stop” for programming language

Statement ;

\n – slash n means new line , if you want to display two sentences one followed by other then use the \n character and if you don’t use it ,everything will appear in the same line

getch() – again we can see that it is a function , the function of this function is to hold the console until it gets an input from the keyboard and when we press any key the programs stops , if you have difficulty in understanding this then remove the “getch();” command and see how the program behaves and then add it again to see what do I mean here

working on more
pl write to me if you want more elaborate explanation of a topic listed ,
thank you

Variables and Data Types

2012-07-30T04:00:00.001-07:00

Ok lets learn the two very important concepts in C programming , variables and data types.

So as the name suggest variable is something that is not constant that varies , we use variable in programming to store data , that could be numbers or text and data type defines the type of the data stored in the variable , so let me give an example to make it easy

Lets sat we want to store someone phone number in a program and display the number , so where we are going to store the number , we store it in a variable named “phone” (variable names are user defined , we give names to the variable , but there are some rules to follow , which I will explain very shortly)

So this would look like

Phone = value ;

Here value can be any integer

So this becomes

Phone = 123456;

This implies that phone is a variable to which we have assigned a value 123456

Now we also have to tell the compiler that “phone” can store what kind of value , like an integer or a character or a decimal value and so on and we tell this by using data type which tells the compiler what is the type of data the variable can store , there are different key word for different data type and the major types are

int for integer value

char for storing individual characters

float for decimal value

double same as float but can store larger numbers

please note that every data type has predefined range within which we can store values which we would discuss shortly

So to use a variable we write

int phone = 123456;

technically speaking variables are named piece of memory that we can assign a value , if you find that difficult , consider variables as a kind of box that we use to store data , the label of the box is its name and the type of content inside the box is its data type and the content is the value

Some rules to follow while naming a variable are as follows

1 > no two variables should have the same name in other words variables should be unique

2> variables name cannot begin with a number for example 123baby

3> variables can only have a to z , A to Z , 0 to 9 and underscore in it

4> variable have to be declared before they are used that means to specify the data type ,

Syntax for variable declaration is

Data type variable_name = value_of_varibale ;

let’s find more about the integer data type

Data Type	Byte	Range
int	4	–2,147,483,648 to 2,147,483,647

In the above table the byte field represents the maximum size of a number an integer data type can hold and range displays that the number could be between negative 2,147,483,648 to positive 2,147,483,647 , so how we are getting this value ,
well for information every data type has a certain range but to understand the relation between byte size and range let us do some binary calculation

So computer stores everything in bits that is zero or one , now 4 byte is equal to how many bits ,

since 8 bit is 1 byte so 4 byte will be 32 bit

8 bit = 1Byte

4Byte = 8 * 4 = 32 bit

So in binary if we have 32 numbers of 1s then the value in decimal form will be 4,294,967,295 but since int can store both negative and positive value this number splits in two equal parts including 0 , so the range splits in half to –2,147,483,648 to 2,147,483,647 , but if we add these two values we would get 4,294,967,295 , this is how we get the range from size , if possible try to find the other range by yourself ,
This link might be helpful to you Microsoft library

Enough with variables and data types now let us do a program with variable

main()

{

int phone = 123456;

printf("Hello World \n");

printf("Your phone number is %d \n",phone);

getch();

}

This program display hello world followed by 123456

Now let us examine the new elements in the program

int phone = 123456; well this is not new , here we have declared a variable with integer type and assigned a value to it

printf("Your phone number is %d \n",phone); printf is explained before ,
in order to display the variable in the statement we use the %d notation inside the quotes then a comma and then the variable name,
please remember that the position of %d in the statement will decide the position of the variable in the statement , so it %d is before the word number then the variable will appear in that position

Now let us do a program with more numbers of variables

main()

{

int phone = 123456;

int mobile = 9876543;

printf("Hello World \n");

printf("Your phone number is %d and mobile is %d \n",phone,mobile);

getch();

}

This is how we express multiple variable in a statement , here the first %d is for phone and the second for mobile variable

Some examples of how to declare and display other data type are

main()

{

float number = 55.5;

printf("value of number is %f”,number);

getch();

}

main()

{

double number = 44.54;

printf("value of number is %lf”,number);

getch();

}

main()

{

Char car = ‘m’;

printf("value of character is %c”,car);

getch();

}

As we can see we have %f is for floats , %lf is for double and %c is for character

Some Small programs

2012-07-30T03:59:00.002-07:00

A program to convert from celcius to ferenheit

main()

{

float farenheit;

float celcius;

printf("Enter Celcious value........... ");

scanf("%f",&celcius);

farenheit = 32 + celcius * 9 / 5 ;

printf("\n\n %.2f Degree Celcius in Farenheit is.........%.2f farenheit",celcius,farenheit);

getch();

}

Try to do ferenheit to celcius by your own

A program to find the prime numbers between 1 to 100

main()

{

int i,j;

int s;

for(i =1;i<=100;i++)

{

s=0;

for(j=1;j<=i;j++)

{

if(i%j==0)

s=s+1;

}

if(s==2)

{

printf("%d\n",i);

}

getch();

}

A program to check a given number is prime or not

main()

{

int i,num;

printf("Enter a number \n");

scanf("%d",&num);

for(i=2;i<num;i++)

{

if(num%i == 0)

{

printf(" This Is Not A Primt Number ");

break;

}

if(i==num)

{

printf(" This Is a Prime Number ");

}

getch();

}

A program to display odd and even number between 1 to 100

main()

{

int i;

for(i=1;i<=100;i++)

{

if(i%2 == 0)

{

printf("Even Number %d\n",i);

}

else

{

printf("Odd Number %d\n",i);

}

getch();

}

A program to find a given number is even or odd

main()

{

int num;

printf("Enter a number \n");

scanf("%d",&num);

if(num % 2 == 0)

{

printf("Even Number");

}

else

printf("Odd Number");

getch();

}

A program to print febonacci series upto 20

main()

{

int a = 0;

int b = 1;

int i,sum;

for(i = 0;i<20;i++)

{

sum = a+b;

printf("%d\n",sum);

a=b;

b=sum;

}

getch();

      }

A program to find the biggest number from three numbers

#include<stdio.h>

main()
{

//enter three different values

int a,b,c;

printf("Enter 1st Number\n");
scanf("%d",&a);

printf("Enter 2nd Number\n");
scanf("%d",&b);

printf("Enter 3rd Number\n");
scanf("%d",&c);

if(a > b && a > c )
printf("The Largest Number is %d",a);

if(b > a && b > c )
printf("The Largest Number is %d",b);

if(c > a && c > b)
printf("The Largest Number is %d",c);

getch();
}

A program to find the smallest number from three numbers

#include<stdio.h>

main()
{

//enter three different values

int a,b,c;

printf("Enter 1st Number\n");
scanf("%d",&a);

printf("Enter 2nd Number\n");
scanf("%d",&b);

printf("Enter 3rd Number\n");
scanf("%d",&c);

if(a < b && a < c )
printf("The Lowest Number is %d",a);

if(b < a && b < c )
printf("The Lowest Number is %d",b);

if(c < a && c < b)
printf("The Lowest Number is %d",c);

getch();
}

A program to create random numbers

#include<stdio.h>
#include<stdlib.h>

main()
{
int i;

srand(time(NULL));

for(i=0;i<10;i++)
printf("Random Number %6d \n",rand());

fflush(stdin);

getch();

}

A program to create dice rolling effect

#include<stdio.h>

main()
{

int rolls,number,i;

printf("Enter The Number Of Times You Want To Roll The Dice ");
scanf("%d",&rolls);

srand(time(NULL));

for(i=0;i<rolls;i++)
{
number = rand();
number = number % 6;
number++;
printf("\n Dice Rolled %d Number Is : %d \n",i+1,number);
}

getch();
}

A program to find rate of interest

#include<stdio.h>

main()
{
int year,period;
float amount,interest_rate,value;

printf("Enter Amount \n");
scanf("%f",&amount);

printf("Enter Interest Rate \n");
scanf("%f",&interest_rate);

printf("Enter Period \n");
scanf("%d",&period);

year = 1;

printf("\n\n");

while(year <= period)
{
value = amount + interest_rate * amount;
printf("%2d Price %8.2f\n",year,value);
amount = value;
year = year + 1;
}

getch();

}

A program to print multiplication table from 1 to 10

main()
{

int i,j;

int array[10][10];

for(i=0;i<10;i++)
{
for(j=0;j<10;j++)
{
array[i][j] = (i+1)*(j+1);
}
}

for(i=0;i<10;i++)
{
for(j=0;j<10;j++)
{
printf("%3d ",array[i][j]);
}
printf("\n");
}


getch();

}

A program to find average of 5 subjects

#include<stdio.h>

main()
{
int sub1,sub2,sub3,sub4,sub5;
int sum;
float avg;

printf("Enter Subject 1 Marks\n");
scanf("%d",&sub1);

printf("Enter Subject 2 Marks\n");
scanf("%d",&sub2);

printf("Enter Subject 3 Marks\n");
scanf("%d",&sub3);

printf("Enter Subject 4 Marks\n");
scanf("%d",&sub4);

printf("Enter Subject 5 Marks\n");
scanf("%d",&sub5);

sum = sub1+sub2+sub3+sub4+sub5;

avg = (float)sum/5;

printf("Average of The Subjects is %.2f ",avg);

getch();
}

A program to find maximum

#include<stdio.h>

main()
{

int n,i,max;

printf("Enter Total Numbers Of Numbers In The Array\n");
scanf("%d",&n);

int array[n];

for(i=0;i<n;i++)
{
printf("Enter %d Number \n",i+1);
scanf("%d",&array[i]);
}

max = array[0];

for(i=0;i<n;i++)
{
if(array[i] > max)

max = array[i];
}

      printf("The Largest Number in the array is %d ",max);

      getch();

}

A program To find minimum

#include<stdio.h>

main()
{

int n,i,min;

printf("Enter Total Numbers Of Numbers In The Array\n");
scanf("%d",&n);

int array[n];

for(i=0;i<n;i++)
{
printf("Enter %d Number \n",i+1);
scanf("%d",&array[i]);
}

min = array[0];

for(i=0;i<n;i++)
{
if(array[i] < min)

min = array[i];
}

      printf("The Smallest Number in the array is %d ",min
      );

      getch();

}

A program to find average of n numbers

#include<stdio.h>

main()
{

int n,i;
int sum;
float avg;

printf("Enter Total Number of the array \n");
scanf("%d",&n);

int array[n];

for(i=0;i<n;i++)
{
printf("Enter %d number \n",i+1);
scanf("%d",&array[i]);

sum = sum + array[i];
}


      avg = (float)sum/n;

printf("Average Of The Numbers Are %.2f ",avg);

getch();

}

A program to tell the nature of image placed before a lens

#include<stdio.h>
#include<conio.h>
main()
{
float radius,focus,o_distance,i_distance,infinity,beyond_curvature,magni;
char conti,y,n;

printf(" PROGRAM TO FIND THE NATURE OF IMAGE OF A CONCAVE MIRROR ");

printf(" \n\n\n\n                         #                         .              ");
printf(" \n                          #   Concave Mirror     . . .            ");
printf(" \n                           #                       .              ");
printf(" \n                            #                      . Positive     ");
printf(" \n                             #                                    ");
printf(" \n                Focus         #                                   ");
printf(" \n      ..C.........F.......... O.........................          ");
printf(" \n                              # pole                .             ");
printf(" \n   Radius of Curvature       #                      . Negitive    ");
printf(" \n                            #                     . . .           ");
printf(" \n            Negative       #     Positive           .             ");
printf(" \n           .              #             .                         ");
printf(" \n          ...........    #     ...........                        ");
printf(" \n           .                            .                         ");

printf("\n\n\n\n Enter radius of Curvature(in CM) ------- ");
scanf("%f",&radius);

focus=radius/2;

printf("\n\n Focal Length will be at(in CM) -----( -ve ) %f",focus);

printf("\n Centre of Curvature will be at(in CM)-----( -ve )%f",radius);

infinity=3*radius;

beyond_curvature=2*radius;

do
{
printf("\n Enter the Distance of the object fron the Mirror(in CM) ------");
scanf("%f",&o_distance);

i_distance=(1/-focus+1/o_distance)*100;

if(o_distance>=infinity)
{
printf("\n\n Position of the object....................infinity ");
printf("\n\n Image will be formed at Focus (in CM)-----");
printf("\n\n Nature--------\n\n Real\n\n Inverted\n\n Diminished");
}

else if(o_distance>beyond_curvature)
{
printf("\n\n Position of the object....................Beyond Centre of Curvature ");
printf("\n\n Image will be formed between center of curvature and focus(in CM)------");
printf("\n\n Nature--------\n\n Real\n\n Inverted \n\n Diminished");
}
else if(o_distance==radius)
{
printf("\n\n Position of the object....................at centre of curvature ");
printf("\n\n Image will be formed at centre of curvature(in CM).........");
printf("\n\n Nature--------\n\n Real\n\n Inverted\n\n Same size");
}

else if(o_distance>focus)
{
printf("\n\n Position of the object....................Between centre of curvature and focus ");
printf("\n\n Image will be formed at Beyond center of curvature ");
printf("\n\n Nature--------\n\n Real\n\n Inverted\n\n Magnified ");
}

else if(o_distance==focus)
{
printf("\n\n Position of the object....................at focus ");
printf("\n\n Image will be formed at infinity ");
printf("\n\n Nature--------\n\n Real\n\n Inverted\n\n Hypermagnified");
}

else if(o_distance<focus)
{
printf("\n\n Position of the object....................Betweew pole and focus ");
printf("\n\n Image will be formed behind the mirror ");
printf("\n\n Nature--------\n\n Virtual\n\n Erect\n\n Magnified");
}

else
{
}
printf("\n\n\n image distance = %f",i_distance);
if(i_distance<0)
{
printf(" To the LeftHand side of pole ");
}
else
{
printf(" To the RightHand side of pole ");
}
magni=i_distance/o_distance;
printf("\n Magnification is = %f",magni);
printf("\n\n Do you want to change the object position (y/n) ");
scanf("%s",&conti);

}
while(conti=='y');

getch();
}

//feel free to modify the logic according to your need if neede

A program to display the place value of a number (upto Billion Only)

#include<stdio.h>

main()
{

long int digit[10];
char place[30][30] = {"Ones","Tens","Hundreds","Thousands","Ten Thousand","Hundred Thousand","Million","Ten Million","Hundred Million","Billion"};
long int data[10];

/* count number of digits */
int c = 0; /* digit position */
int n ;
int i;
int number;

printf("enter a number\n");
scanf("%d",&n);
number = n;
while (n != 0)
{
n /= 10;
c++;
}

printf("the number of digits int the number is %d\n\n\n",c);
int numberArray[c];

for (i = 0; i < 10; i++) {
numberArray[i] = number%10;
number = number / 10;
}

int j = 10;

digit[0] = 0;

for(i = 1;i<10;i++)
{

digit[i] = j;

j = j * 10;

}

for(i = 0;i<10;i++)
{
printf("%d__________%5s____________%d\n\n",digit[i],place[i],numberArray[i]);
}

getch();
}

A program to tell Horoscope

#include<stdio.h>
#include<conio.h>
main()
{
int select,option;
int c,p,a,ar,t,g,ca,l,v,li,s,sa;
char y;

printf("\n                              Select your Zoic Sign \n");
printf("\n                                  1 CAPRICORN");
printf("\n                                  2 AQUARIUS");
printf("\n                                  3 PISCES");
printf("\n                                  4 ARIES");
printf("\n                                  5 TARUS");
printf("\n                                  6 GEMINI");
printf("\n                                  7 CANCER");
printf("\n                                  8 LEO");
printf("\n                                  9 VIRGO");
printf("\n                                  10 LIBRA");
printf("\n                                  11 SCORPIO ");
printf("\n                                  12 SAGGITTARIUS \n\n                                       ");
scanf("%d",&select);

switch(select)
{
case 1:
printf("\n\n                           You Have Selected CAPRICORN \n\n ");
printf("\n            Your Date of Birth Lies between 1st December to 20th January \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&c);
     switch(c)
     {
     case 1:
     printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Money Forms an important partof your life and reaching your full potential is   something you worry about\n You have the ability to earn good money throygh life but are sometimes hindered for the lack of opportunity you have\n\n Working in a structured environment is oftenthe best and the most successful    way you work\n although partnerships may also bring about success.\n You are prone to suffring from stress related illness like headaches and back   pain so don't over do it");
     break;

     case 2:
     printf("\n\n.................................Friends and Companions..........................\n\n");
     printf(" You have a amicable personality and therefore a large circle of friends very    few you are intimate with\n You are very loyal to choose friends and people ofen see you as a soldier to    cry on because of your good nature\n Intimate companions will normally be born under pisces , virgo , scorpio and    cancer");
     break;

     case 3:
     printf("\n\n....................................Personality.................................\n\n");
     printf(" You are a very talented , courageous , truthful , individual.\n You have a clear views on things and are at times painfully frank.\n You have a quick temper and because of this often say things you latter regert ");
     break;
     }
break;

case 2:
printf("\n\n                           You Have Selected AQUARIUS \n\n ");
printf("\n            Your Date of Birth Lies between 21st January to 19th February \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&a);
     switch(a)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Your impressionable nature means you are often taken advantage of financial     situations.\n People often see you soft touch and you must overcome this if you asr to reach the hights of your desire.\n You are quit unlucky in speculative ventures and should avoid gambling\n\n Your love of natural beauty and high degree of energy means that professions in the performing arts , teaching , artistry , medicine and other science would    suite you well ");
     break;

     case 2:
      printf("\n\n.................................Friends and Companions.........................\n\n");
     printf(" Your appreciation of intellectual beauty through your love of poetry and art    means that you enjoy being in the company of intelligent people.\n Although you have many friends who admire you very few are close to you.\n You get on best with people born under libra , gemini and aries ");
     break;

     case 3:
      printf("\n\n....................................Personality.................................\n\n");
     printf(" You are energetic , loving and inspirational and are often seen as an attention speaker\n You have a love of natural beauty , ars and mugic.\n You often have a sence of mystic and a fascination with physic abilities ");
     break;
     }
break;

case 3:
printf("\n\n                           You Have Selected PIECES \n\n ");
printf("\n            Your Date of Birth Lies between 20th Febuary to 20th Mars \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&p);
     switch(p)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Your financial situation vill vary greatly during your worling career.\n At other time it will be more difficult.\n Your turbulent relationship with   money means that it is important for you to put money away for harden times ahed.\n You are hard working although your pessimstic nature means you tend    to worry too much ");
     break;

     case 2:
      printf("\n\n..................................Friends and Companions........................\n\n");
     printf(" Your ability to communicate well with people means you will always have a large group of friends\n However people find you rather hard to understand because of your dual personalities. ");
     break;

     case 3:
      printf("\n\n....................................Personality..................................\n\n");
     printf(" You are generous and loyal to friends and kind hearted.\n At times you appear to have dual personality as you can be two totally          different individuals.\n Overall you tend to have a pessimistic attitude towards things which you need   to fight.\n You posse's good communication skills and have good foresight. ");
     break;
     }
break;

case 4:
printf("\n\n                           You Have Selected ARIES \n\n ");
printf("\n            Your Date of Birth Lies between 21st Mars to 20th April \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&ar);
     switch(ar)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Inclined to be impulsive which you need to come to terms with to succeed.\n You have the ability to attain fincial independence if you do not spread your   efforts too much.\n If you can learn to coordinate your mind and body success will be assured.\n You are practical and always tyr to improve the ways you do things ");
     break;

     case 2:
      printf("\n\n..................................Friends and Companions........................\n\n");
     printf(" You will have large group of friends and admirers and will go to extremes to   defend friends you fell are unjustly threatened.\n You have an ability to make friends very easy and are excellent social mixer    because of your entertainning personality ");
     break;

     case 3:
      printf("\n\n....................................Personality.................................\n\n");
     printf(" Determined , industrious and practical minded.\n You tend to be blunt and plain spoken with a high degree of eloquence.\n You are inclined to be impatient and regard your opinions and judgement to be   as good as others ");
     break;
     }
break;

case 5:
printf("\n\n                           You Have Selected TARUS \n\n ");
printf("\n            Your Date of Birth Lies between 21st April to 21st May \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&t);
     switch(t)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Although mney will never be a problem for you throughout life , it does tend to burn a hole in your pocket.\n You need to control your spending if you want to complete fincial stability in later life.\n Your determination and ambitious nature means you are a hard working and        diligent employee .\n You will have successful career and are capable of achieving greats hights ");
     break;

     case 2:
      printf("\n\n....................................Friends and Companions.......................\n\n");
     printf(" Through your personality traits you will have many friends who admire your      loving and honest nature.\n You enjoy sharing your life with others and have lot of devoted friends. ");
     break;

     case 3:
      printf("\n\n....................................Personality.................................\n\n");
     printf(" You have an ambitious and determined nature and are cautions , lovind and      honest.\n At time you can be stubborn and people find it hard to change your opinion of   things.\n You are often guided by your deep emotions and have a friendly and optimistic   character ");
     break;
     }
break;

case 6:
printf("\n\n                           You Have Selected GEMINI \n\n ");
printf("\n            Your Date of Birth Lies between 22nd May to 21th June \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&g);
     switch(g)
     {
     case 1:
     printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Your fincial position will alter greatly throughout life.\n At times money will come easy , at other times less so.\n Putting money away for the future is the best strategy for you.\n You open mindeness will serve you well at work where you will adapt well to     changing environment and new tasks.\n Your slight nervousness may hinder you so try overcome this ");
     break;

     case 2:
     printf("\n\n..................................Friends and Companions........................\n\n");
     printf(" You will be regarded as a soulder to cry on by both close friends and more      distance ones.\n Your sensitive nature attracts people to share their worries with you .\n You will have few very close friends who you can turn to ");
     break;

     case 3:
     printf("\n\n....................................Personality.................................\n\n");
     printf(" You often have a nervous temperament but are sensitive , Cautious and versatile.\n You have an innovative nature and an inquisitive mind and enjoy scoring out     information on subjects that interest you.\n This means you develop an depth understanding of such topics ");
     break;
     }
break;

case 7:
printf("\n\n                           You Have Selected CANCER \n\n ");
printf("\n            Your Date of Birth Lies between 22nd June to 23rd July \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&ca);
     switch(ca)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Your sign displays clear signs of wanting to save money.\n You like to gamble once in a while and are generally a lucky person as long as you follow your instincts and are not influenced by others.\n In your working career you are thorough and methodical-A lateral thinker.\n You like being motivated and can easily become down if you are not encouraged ");
     break;

     case 2:
      printf("\n\n..................................Friends and Companions........................\n\n");
     printf(" Surrounded by a large group of friends you are generally very popular.\n You will feel happy confiding in close friends who always have your best        interests at heart. ");
     break;

     case 3:
      printf("\n\n....................................Personality................................\n\n");
     printf(" You are extremeley sensitive character with a friendly and loving nature but    often be irritable and moody.\n Living in a world of your own you are a bit of daydreamer.\n In your community you are a popular person. ");
     break;
     }
break;

case 8:
printf("\n\n                           You Have Selected LEO \n\n ");
printf("\n            Your Date of Birth Lies between 24th July to 23rd August \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&l);
     switch(l)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Your financial affairs will have many ups and downs. It is therefore important that you invest early on life to provide for your future.\n External fincial support will come from close friends and relative at time when you most need it.\n In your working career you have the ability to achieve great successes.\n Your ambitious nature coupled with good problem solving skills make you a       valuable addition to any business   ");
     break;

     case 2:
      printf("\n\n..................................Friends and Companions........................\n\n");
     printf(" You will have a large circle of friends who like your generous and enthusiastic personality.\n People find you slightly hot headed and impatient ");
     break;

     case 3:
      printf("\n\n....................................Personality.................................\n\n");
     printf(" You have a ambitious , generous and determined nature .\n You easily looses your temper and become restless.\n Akey strength that you posses is your ability to adapt to almost any situation you are put in ");
     break;
     }
break;

case 9:
printf("\n\n                           You Have Selected VIRGO \n\n ");
printf("\n            Your Date of Birth Lies between 24th August to 23rd September \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&v);
     switch(v)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" Fincial success will be achieved through exploiting your artistic abilities .\n Your methodical and intellectual nature means that when you find a profession   in life that is well suited to you ");
     break;

     case 2:
      printf("\n\n..................................Friends and Companions........................\n\n");
     printf(" Your strong desire to succeed means that you appreciate the finer things in     life , This in turn influnce the social circle you move in.\n You choose your friends very carefully and generally they are of a similar      nature to you ");
     break;

     case 3:
      printf("\n\n....................................Personality..................................\n\n");
     printf(" You often have a nervous temperament, but are sensitive , cautious and          versatile.\n You have an innovative nature and an inquisitive mind and sourcing out          information on subjects that interest you ");
     break;
     }
break;

case 10:
printf("\n\n                           You Have Selected LIBRA \n\n ");
printf("\n            Your Date of Birth Lies between 24th September to 23rd Octobor \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&li);
     switch(li)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" If you can fulfil your full potential you have the ability of achieve a high    level of wealth.\n Money does tend to burn a hole in your pocket through.\n Wise investments early in your life will assure you of a secure future.\n You will have a successful carrer through your way of work. ");
     break;

     case 2:
      printf("\n\n...................................Friends and Companions.......................\n\n");
     printf(" You choose your closest friends carefully although they are often of a totally different nature to you.\n You enjoy spending time alone . ");
     break;

     case 3:
      printf("\n\n....................................Personality.................................\n\n");
     printf(" You are a well balanced individual.\n You are loving , selfish and idealistic .\n You have a forgiving and sympathetic nature, although you can be slightly hot   tempered at times ");
     break;
     }
break;

case 11:
printf("\n\n                           You Have Selected SCORPIO \n\n ");
printf("\n            Your Date of Birth Lies between 24th Octobor to 22nd November \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&s);
     switch(s)
     {
     case 1:
      printf("\n\n...................................Work and Finance.............................\n\n");
     printf(" Although you will not fulfil your full capabilities until later life, you will set a steady growth in fincial status as your career progresses.\n Your good sence of humour and laid back approch to life will mean that you are able to take on anything that falls in your path ");
     break;

     case 2:
      printf("\n\n...................................Friends and Companions.......................\n\n");
     printf(" People enjoy your company but dislike the way you try to dominate all           situations.\n You enjoy spending time with those who have a similar sense of humour to you    and share your laid back approach on life ");
     break;

     case 3:
      printf("\n\n....................................Personality.................................\n\n");
     printf(" You have a generous , sympathetic and determined nature.\n You are well liked by friends and colleagues because of your sence of humour ");
     break;
     }
break;

case 12:
printf("\n\n                           You Have Selected SAGITTARIUS \n\n ");
printf("\n            Your Date of Birth Lies between 23rd November to 21th December \n ");
printf("\n                                  Choose a Catagory\n");
printf("\n                                  1 Work and Finance \n");
printf("\n                                  2 Friends and Companions \n");
printf("\n                                  3 Personality \n ");
scanf("%d",&sa);
     switch(sa)
     {
     case 1:
      printf("\n\n....................................Work and Finance............................\n\n");
     printf(" You are extreamely resourceful. You like to work on your own ideas.\n Your fincial status will grow with your experience . You are a bit impulsive in your work ");
     break;

     case 2:
      printf("\n\n....................................Friends and Companions.......................\n\n");
     printf(" You do not have a large circle of friends.\n People often regards you as a workaholic and become jealous of your success in later life ");
     break;

     case 3:
      printf("\n\n....................................Personality.................................\n\n");
     printf(" Your overall outlook on life is very positive and you have a high degree of     intelligence.\n You are happy to share all that you own with those around you.\n You are slightly hot tempered and are easily upset ");
     break;
     }
break;

default:
printf("................................Invalid Parametre............................... ");

}

getch();
}

Compilation Process

2012-07-30T03:58:00.005-07:00

Before discussing the actual compilation process let us discuss the c program structure of a typical c program which consist of the following component

.c files , standard c libraries , other c libraries

These components combined together to form a c program , let us now see what is the meaning of this components

.c files - it is the file that contains the source code , there could be a single c file or multiple .c files for a single program

Standard c library - all the definitions of functions like printf() , scanf() , puts() ,getch() etc are to be found in the standard c library , standard c library contains pre compiled codes that we can use in our program to make software development faster

Other c library - it may be possible that we need some functionality in our program that is not available in the c standard library , in this case we can use libraries that are not of c standard library , for example we may want to connect to a database using c program and for this we may have to import a library for our database program

So that will be the structure of a typical c program , now let us examine the compilation process

The actual compilation process can be sub divided into three broad groups

Pre processing / pre compilation

Compilation

Linking

Let us examine the three processes in detail

Pre processing or pre compiling - it can be said as processing that happens before the compilation process , during this process all the .c files are pre processed , sometime it is done in the memory and sometime it is done by creating a temporary file by the compiler ,In this process all the pre processor directive like #define , #include are processed as well as all the comments are removed

Compiling – during this process the coding is converted from human readable form to machine readable form and we get a object file , other things that happens in this process are syntax checking , prototype checking , variable checking etc

One thing to notice is that , if our program has only one c source file then we may not get the object file and directly end up with the exe file

Linking – it is the final stage in which all the necessary file that will be the object file , c standard library files and other library files are linked together to form a executable file having a .exe extension

We have talked about c program structure and compilation process , now we will talk about memory regarding c programs

The memory can be divided into four groups

Static

Stack

Dynamic

Program

Let us examine the above in detail now

Static – all the global variable and static variables are stored in this part of memory , this memory is called when program is started and is destroyed when the program ends

Stack – all local variable and function parameter are stored in this part of the memory , the lifetime of these variable ends when the block that they are in ends

Dynamic – it is also called as heap memory , it is allocated by the operating system when required by the programmer , a pointer is used to use this memory

Program memory – this memory contains the object code of the executable file , this memory is never modified during the course of execution

Pointer Reloaded

2012-07-30T03:58:00.002-07:00

Pointers are considered one of the most confusing concepts in c , so I would try to explain it in a more detail and vivid way ,

Ok first of all let us consider a stack of 10 boxes and each box has a location in the stack like 1^st box , 2^nd box up to 10^th box , now let us think that we have stored an integer in each of the box like 99 , 87 , 76 and so on as shown in the figure below

Now let us give a name to the box number 5 and called it as “x” , so basically we have done this

X = 2

And this x = 2 is in which box ?

It is in 5^th box , that will be the address of that box

Now when we say to someone about “x” , what do we mean by “x” ?

We mean the value stored in x that will be in our case is 2 , so it will be like this

X = value stored in x

And if we say what is the address of “x” then what will we say ?

5^th box is the address of x , which in a c language syntax we can write as

&x = 5^th box = address of x

Always remember that the ampersand sign “&” means address of something

Now if we ask , what is the content of the 5^th box ?

The answer would be 2 , but instead of asking directly that what is “x” , we are indirectly asking the value of x from the address point of view or in our example box position , in c language this is represented as

*address of the box number 5 = * 5^th box , both these expressions will give the same value below

*address of the box number 5 = x = 2

So we see that it is possible to get the address of a value and also user this address to access the value itself

&x = address of x

*address of x = contents of x

As seen in the figure above all the address of the boxes can be accessed using the “&” sign and all the contents of those addresses can be accessed using the “*” symbol

So now we can say

X = 2

&X = address of X

*address of x = 2

In a programmatic form the above lines can be represented as

main()

{

int x = 2;

printf("value of x is %d\n",x); //display the value of x that will be 2

printf("address of x is %d\n",&x); //display the address of x that will be a long number

printf("contents in the location %d is %d",&x,*(&x));

//display address of x and then the contents in that address , that will be 2

getch();

}

See in the last printf statement we use “*(&x)” which is nothing but in English is

“the contents of the memory location whose name is x “ and that is 2

This is the concept of pointers , so if you think you are done in understanding pointer concepts then answer me this

We know that from the above example

X = 2

&X = address of X

*address of x = 2

Now if I ask you what will be the answer to the following expression

*X = ? ? ?

Can you answer this ,

I can give you a hint , , , “to answer this you have to look at the box diagram above”

Be honest with yourself

Ok let me give you the answer , it will be

*X = 87

If you have got the answer then you got it but if not then let me explain it to you

*X means in English “the contents of the box having the address x” and in our case x is 2 , so the expression means *2 or we can say “the contents of the box at second position” that is in our case is 87 , hope you got it this time but if not then my next example might help you

Instead of thinking all about these memory and memory addresses let us think about a magic show and the name of the magic show is “main function show” , there are 6 chairs in the magic show for audiences to watch and because of rain 5 of them were unable to attend the show , so 5 chairs are empty but Mr. Cat who likes magic show very much was present at the show and waiting for the show to start as we can see in the figure below

Now let us imply the knowledge from the first example (box example) and see what will be the results for each expression

& Mr. Cat = address of Mr. Cat , that will be 2^nd Row , 2^nd Seat

& Mr. Cat = 2^nd Row , 2^nd Seat

And if we use the “*” operator then this will be

* 2^nd Row , 2^nd Seat = Mr. Cat

This is the same thing as saying

&X = address of X and * address of X = X

This is the concept of pointers , hope this time it is clear with you , but how to use pointers in a actual c program , let me give you a actual c program for this

main()

{

int x = 100;

int *pointer;

pointer = &x;

printf("Address of X is %d\n",pointer);

printf("Pointer is pointing to x which contains %d",*pointer);

getch();

}

Hmmmm its look different but trust me it implies the same logic that we have studied so far , let me explain it line by line

int x = 100; = this is not very difficult to get , we declare a variable called X which is of integer type and set the value as 100

int *pointer; = this looks different , but let me explain , now if we remove the “*” sign from the expression what will we get , something like this int pointer , but this is nothing but a integer variable declaration , but the adding of the “*” symbol before the pointer word makes it a special variable , a variable that have the ability to store memory address of other variable and in our case an integer variable , int *pointer means a pointer variable of integer type , if there was flaot instead of int then it will mean that the pointer can store address of a variable of float type

so to sum it up here we declare a special variable that have the ability to store addresses of other variables

pointer = &x; = in the code above we declare a variable that can store the address of other variable , but we have not specified which address to store , In this code we specify the pointer to store the address of x , &X which is the address of x is now stored in the pointer which is a special type of variable which can store addresses

printf("Address of X is %d\n",pointer); = we display the address of X which is stored in the special variable pointer

printf("Pointer is pointing to x which contains %d",*pointer); = now if we want to display the value of x indirectly through the use of the pointer we use *pointer which in English means show the contents of the variable whose address is stored in the pointer

This is how pointers are used in actual c programming , next I am going to explain the uses of pointer or the main use of pointer

Function parameter = whenever we pass something to a function we actually are not passing the original value we are just passing a copy of the original value , which sometimes becomes a problem and also consumes more memory , if our program is small then it might work well but in case of large scale program this would create a bug in the program , so we use pointers which gives us the ability of manipulating the original value

To better get it , let us see an example

void function_no_pointer(int x)

{

x = x + 1;

printf("Inside Function function_no_pointer %d \n",x);

}

void pointer_function(int *x)

{

*x = *x + 1;

printf("Inside pointer_function %d\n",*x);

}

main()

{

int xM = 5;

printf("xM originally was %d\n",xM);

function_no_pointer(xM);

printf("Inside main function %d \n\n\n",xM);

int yM = 88;

int *ptr;

ptr = &yM;

printf("yM originally was %d\n",yM);

pointer_function(ptr);

printf("Inside main function %d \n",yM);

getch();

}

This is a very simple program which just calculate the next number for variables xM and yM which we have already defined as 5 and 88 , we pass these values to two functions which just adds 1 to them and display the result

Now notice that inside the main function we have declared xM as 5 , we then pass it to function called “function_no_pointer” which just adds 1 to the value of xM , we also display the result from inside this function which is 6 and also from inside main function , but inside main function xM is still 5 not 6 because we have just incremented a copy of xM, but the original xM is intact , so if we want to edit the original variable we have to use pointers as in the second function

Now we have declared a second variable called yM and also a pointer ptr which contains the address of yM , now we pass ptr to a function caller “function_pointer” and do the calculation from the address point of view , now we display the result from inside this function and also from inside the main function and in both case the result is 89 , so we have been able to change the original value this time by using pointers

Function pointers = we can even pass a function as a pointer , it is same as regular variable pointer . Let us see an example to better understand this concept

int add_function(int x , int y)

{

return x + y ;

}

main()

{

int z = 0;

int (*function_pointer)(int , int);

function_pointer = &add_function;

z = (*function_pointer)(5,4);

printf("%d",z);

getch();

}

First we have a function called “add_function” which accepts two integers and returns the addation of the two integers , now inside the main function we declare a function pointer like this

int ( *function_pointer ) ( int , int ) ;

as we can see this is a function pointer which accepts two integers and return an integers , notice the “*” operator before the name “function_pointer” which signifies that this is a function pointer , now this function pointer is not pointing to any function so to do that we write the following code

function_pointer = &add_function;

from the above code of line we now store the address of the “add_function” function on our function pointer or initialized our function pointer

z = ( *function_pointer ) ( 5 , 4 ) ;

after declaration and initialization of our function pointer we can use our function pointer to actually do something , here we are passing two integers to the “add_function” by using function pointers and storing the result in the variable called “Z” and displaying the result

This is a very simple example of how function pointers can be used in our programs

Pointers and structures = structures are very important part of c programming which can be used for user defined data types , now let us say we have created a structure , fill the structure with data and now we pass the structure to a function , So in this case what happens is that that a copy our structure is made and this copy is passed to the function , In case of large scale structures it will consume more memory and also will make our program slow , So to handle this situation instead of passing a whole structure we pass a pointer pointing to the structure , let us see an examples of it

struct my_structure

{

char first_name[20];

char last_name[20];

int age;

int id_number;

};

struct my_structure my_s;

display_result(struct my_structure *pointer)

{

printf("Information in my_structure is \n%s \n%s \n%d \n%d \n\n\n",

pointer->first_name,pointer->last_name,pointer->age,

pointer->id_number);

strcpy(pointer->first_name,"Agent");

strcpy(pointer->last_name,"007");

pointer->age = 99;

pointer->id_number = 99999999;

printf("Information in my_structure is \n%s \n%s \n%d \n%d ",

pointer->first_name,pointer->last_name,pointer->age,

pointer->id_number);

}

main()

{

struct my_structure *structure_pointer;

structure_pointer = &my_s;

strcpy(structure_pointer->first_name,"James");

strcpy(structure_pointer->last_name,"Bond");

structure_pointer->age = 70;

structure_pointer->id_number = 12345678;

display_result(structure_pointer);

getch();

}

In this example we first declare a structure called “my_structure” having the appropriate fields and also “my_s” of “my_structure” type

Now we have a function called “ display_result” which accepts a structure pointer type of type “my_structure”

Now inside main function we declare a structure pointer

struct my_structure *structure_pointer;

and assign this pointer to “my_s” of “my_structure” type

structure_pointer = &my_s;

now we use structure pointer to assign values to the fields of “my_structure” and pass “structure_pointer” to “display_result” function which accepts a structure pointer as its parameter

inside “display_result” we display the fields and also assign new set of values to “my_structure” through the use of pointers

pointers and array = we can use array and pointers side by side with each other or replace arrays with pointers or pointers with arrays , but they have to be declared first , One point to remember is that the size of a pointer is not the actual size of the array because pointers only store the address of the array which is in a 32 bit system is 4 byte

following example can help us to understand the use of pointers and array

main()

{

int i;

int array[] = {1,2,3,4,5};

int *pointer;

pointer = &array;

for(i=0;i<5;i++)

{

printf("%d\n",pointer[i]);

}

getch();

}

One point to remember is that when we assign a pointer to an array we actual store the address of the first index of the array in the pointer

Pointer to pointer = it is possible to assign a pointer to a pointer , which means we have a pointer which stores the address of a variable and another pointer which stores the address of that pointer , but I will not only show you pointer to pointer but pointer to pointer to pointer

main()

{

int x = 100;

int *p1;

int **p2;

int ***p3;

int *pt1,*pt2,*pt3;

p1 = &x;

printf("address in p1 is %d\n\n",p1);

p2 = &p1;

printf("address in p2 is %d\n\n",p2);

p3 = &p2;

printf("address in p3 is %d\n\n",p3);

printf("content of pointer p1 : %d\n",*p1);

printf("content of pointer p2 : %d\n",*p2);

printf("content of pointer p3 : %d\n",*p3);

pt1 = p1;

printf("\n\naddress in pt1 is %d\n",pt1);

pt2 = pt1;

printf("address in pt2 is %d\n",pt2);

pt3 = pt2;

printf("address in pt3 is %d\n",pt3);

printf("\n\ncontent of pointer pt1 : %d\n",*pt1);

printf("content of pointer pt2 : %d\n",*pt2);

printf("content of pointer pt3 : %d\n",*pt3);

getch();

}

In the above example we first declare a integer variable “X” and then three pointers p1 , p2 , p3 , notice the increasing “*” symbols with pointers , which signifies that they are pointer to pointer and pointer to pointer to pointer

Now we assign the address of x in p1 and display the address , then we pass the address of p1 into p2 and display the address and finally we pass the address of p2 into p3 and display the address , we also display the contents of the pointers or the thing the pointers are pointing to , for p1 it will be the value of x but for p2 and p3 it will be the address of the former pointer

We also declare three pointers pt1 , pt2 and pt3 . Pt1 stores p1 , then pt2 stores pt1 and finally pt3 stores pt2 and display their address and contents

This might look confusing , so I have included a screenshot of the output , so that you can relate it with the program

Coming soon

Dynamic Memory

2012-07-30T03:57:00.005-07:00

Dynamic memory is the process of obtaining memory by the programmer in the program by requesting the operating system to allocate memory and if memory is available then the operating system allocates memory to the program

Dynamic memory is created when we need it and destroyed when we are finished with it , we use the malloc function in order to obtain memory from the operating system , mellocs are used extensively used with pointers in order to function properly

The syntax looks like

#include<stdlib.h>

int * ptr

ptr = malloc(100);

we have to use the c standard library stdlib for the malloc function to function ,

we create a pointer pointing towards an integer

now we use the pointer to assign memory of 100 bytes , but instead of typing a number we can write the following

ptr = malloc(25 * sizeof(int));

the above syntax means that we need memory for storing 25 integers so we have 25 multiply by size of a int that would in most case 25 * 4 = 100 byte

some malloc programs are

#include<stdio.h>

#include<stdlib.h>

main()

{

int i;

int sum = 0;

float ans = 0;

int total;

int *avg;

printf("Total Numbers Of Number \n ");

fflush(stdin);

scanf("%d",&total);

avg = malloc(total * sizeof(int));

if(total == NULL)

{

printf("malloc error \n");

exit(1);

}

for(i=0;i<total;i++)

{

printf("Enter number %d ........ \n",i+1);

fflush(stdin);

scanf("%d", &avg[i]);

sum = sum + avg[i];

}

free(avg);

ans =(float) sum/total;

printf(" Average is %f ",ans);

getch();

}

In this program we ask the user for a number that would be the total number of number of which we would find average , we store this value in “total” , now we ask the OS to allocate memory for that amount integer and we use a pointer to refer to it “avg” , sometime the system may not be able to provide memory so to tackle this situation we have written this piece of code

if(total == NULL)

{

printf("malloc error \n");

exit(1);

}

Which means if no memory is available then exit the program , now we use a for loop which runs the “total” time and with each run we accepts a number from the user which is summed up in the variable sum , then we free the memory used using the free function and finally we display the average

Static keyword

2012-07-30T03:57:00.002-07:00

It is not a very complicated concept , if we use static with global variable then it restricts the scope of that variable to the program in which the variable is declared only same with function also

Static functions are only visible to the source code containing the function only , but if we declare a local variable static that means the lifetime of that variable will be from the first function call to the ending of the program otherwise local variable dies as soon as the function in which they are declared is over

static int x = 20; // global variable

static hello() //static function

{

static int y = 0; //static local variable

}

main()

{

hello();

getch();

}

File IO

2012-07-30T03:56:00.003-07:00

A file can be defined as a location on the disk where we store logically related data under a same name

In c programming we can make file in which we can store and retrieve data

Before writing data to a file we first have to define a file and we do this by using the following syntax

FILE *fp ;

Fp = fopen(“file name”,”mode”) ;

In the first line of the syntax we declare a pointer “*fp” which is of FILE type , it is a special type which handles files

Now we use this pointer to open a file , this is very important , weather we want to read or write to a file we first have to open it and we do this by using “fopen” which means “file open”

fopen takes two parameter , one is the file name and other is the mode . Mode can be read , write or append which is represented by keywords “r” , “w” , “a”

after we open the file , we can manipulate the file and then we close the file . Closing of the file is done by writing

fclose( fp ) ;

let us now see a program which creates a file and writes characters to it

#include<stdio.h>

main()

{

FILE *fp;

char c;

printf("Enter Data\nTo finish writing press enter then type ctrl + z to end\n\n");

fp = fopen("f:\\file one.txt","w");

while((c=getchar())!=EOF)

{

putc(c,fp);

}

fclose(fp);

printf("Press Enter To Exit\n");

getch();

}

We have seen how to write characters to a file , now let us see how we can read data from a file we have created

#include<stdio.h>

main()

{

FILE *fp;

char c;

printf("The Contents Of The File\n\n");

fp = fopen("f:\\file one.txt","r");

while((c = getc(fp)) != EOF)

{

printf("%c",c);

}

fclose(fp);

getch();

}

Soon going to update more

Pointers

2012-07-30T03:56:00.000-07:00

Well pointers are the most important part in c programming and it is very important to understand pointers because they are very confusing , so lets get started

Pointers can be defined as variables that stores the address of other variable

Address means the name of the location on the memory where we store our variable for example

int x = 10;

so here we have declared a integer variable called x which contain the value of 10 and lets say the memory address if it is 123

In the above diagram lets consider the three box as memory and x = 5 is the box where we have stored our value having the address of 123 , but in real life also we can find the address of a variable with this piece of code

main()

{

int x = 10;

printf("address of x is %d",&x);

getch();

}

We have stored our variable , given it a value and also find its address

pointers are also variables that stores the address of other variables and also have the power of manipulating them

In the above diagram we have declared a pointer “ptr” which contains the address on int x =10 , we can also use pointers to change the value of x , so let us see the syntax of how to use pointers

int x;

int *ptr;

ptr = &x;

*ptr = 12;

So let us examine the steps

int x; = in this step we just declared a integer without any value to in

int *ptr; = this is how we declare a pointer , notice the star symbol , if you remove the "*" then ptr will become just an integer , so "*" means , it is pointer , there is int before the pointer because this pointer is going to store the address of a integer , if int x was float x then then the pointer will be float and so on

ptr = &x; = we have declared the integer and also the pointer but in order to get the address of x and store it in the pointer “ptr” we use this statement , &x means the address of x which we are storing in ptr

*ptr = 12; = this means that the thing the pointer is pointing to change it to the value of 12 , in other words now x from 10 is changed to12 by using a pointer , the above steps in a code looks like this

main()

{

int a;

int *ptr;

ptr = &a;

*ptr = 123;

printf(" value of a is %d\n\n",a);

printf(" value of a is %d",*ptr);

getch();

}

We can also use pointers as function parameter for example

#include<stdio.h>

double_it(int *x) //pointer to accept the address of y

{

*x = *x * 2; //thing the pointer points to (that is the VALUE of y)

} // = thing the pointer points to (VALUE of y) * 2

main()

{

int y;

printf("enter number \n");

scanf("%d",&y);

double_it(&y); //pass address of y

printf(" double is %d",y);

fflush(stdin);

getch();

}

In the above code we ask the user to give a number which we store in the variable y , we then pass the address of y (&y) to the function double_it which only accepts pointers as a parameter *x , we then multiply the contents of the pointer which the pointer is pointing to by 2 and modify the content , and then we display y

To Know More On Pointers Click Here

Structure

2012-07-30T03:55:00.002-07:00

structure can be defined as a user defined data type that contains a range of other data types . we can say that it is a composite type

lets see example of a structure of a book database

struct structure_name

{

Char title[30];

Char author[30];

Int page;

};

So we can see that the structure starts with a struct keyword followed by the structure name and then we have the different fields of the structure or data type declared

Individual fields of a structure can be assessed by the dot operator

We can declare other variable of the structure we have made

For example

struct employee //structure defination

{

char name[20];

float salary;

int age;

}

main()

{

struct employee emp1,emp2; // structure variable declaration

emp1.age = 28; //assigning vale to the age field of the structure

printf(" age is %d \n",emp1.age); //printing the structure field content

getch();

}

In this example we first define the body of the structure above the main function , then we declare some variable of the structure type and then we use the dot operator with the structure variable to assign value to one of the field of the structure , and last we display the content of the structure

We can pass structure to a function just like any other variable

Function( employee) // passing a structure variable employee to a function

Function_2(struct employee employee2) // accepting the passed value

{

printf(“%d”,employee2.age);

}

We can also return a structure like this

employee1 = read_enployee();

The function look likes this

read_employee()

{

struct employee emp

scanf(“%d”,&emp.age);

return emp;

}

C Functions

2012-07-30T03:54:00.006-07:00

Functions are basic blocks of codes , till now we have been using a lot of functions , can you remember , yes one of it is the prints function , before going to discuss function let us see the syntax for a function

Function name ( function parameter )

{

Function body

}

So function name is quite easy to understand , so the function parameter is what we pass into that function , we can say that it is the doorway for a function

Function body is the part where all the action happens

This figure might help to understand this well

But programmatically how this work , to see this lets make a simple program that display a message from a function outside main and how it works

function()

{

printf(“hello world”);

}

main()

{

printf(“inside main”);

function();

getch();

}

As we can see we are calling the function “function” inside the main by just referring its name , this is how we call a function , we can call as many functions as we want , we can call multiple functions but for that the functions should exist first

One thing to remember is that if a variable is declared inside a function then that variable is just accessible to that function only , in order to make a variable accessible to all the functions we make a global variable , it is nothing but a variable declared at the very above of every function , this example will make this clear

#include<stdio.h>

int total; //global variable

int i;

input() //function

{

printf("Enter a number\n");

scanf("%d",&i); // taking a value and changing the value of i for all function

}

output()

{

total = i *2; // global variable total calculation

}

main() // main fnction

{

input(); // calling input function

output(); // calling output function

printf("total is %d",total); //displaying the total from main

getch();

}

As we can see , "total" and "I" are global variable and input and output are two user defined functions

We can also pass parameter to a different function and then process the result , this example will make this more clear

int total;

take(int a)

{

total = a * 2;

printf("\n\ndouble is %d",total);

}

main()

{

int i;

printf("Enter a number\n");

scanf("%d",&i);

take(i);

getch();

}

Here we take the variable i in main and pass it to function called take , in take inside its parenthesis we declare a variable of same data type that accepts the value of i , once a=I then everything becomes easy now

It is also possible that a function can return a value to the mother function like

int add(int n1 ,int n2)

{

int result;

result = n1 + n2;

return result;

}

main()

{

Int z;

z = add( 3,5);

printf(“%d”,z);

getch();

}

In this program we first pass value to the add function , the int before the function name signify that this function will return a int value , then the add function accepts the value and returns the result which get stored in the variable called z , and we display the “z” , this is how returning of a value works in a function

C pre processor

2012-07-30T03:54:00.003-07:00

These are the part of the program that is processed before the actual compilation of the program , by processing means substitution of some text by another

Let us take an example to make this more clear

Suppose in our program we are using the value pi a lot of time , so instead of writing the value again and again we can write this before the main part

#define PI 3.14;

So now we can replace the value with the word pi in our program like

PI * 20;

Or something like this

This is one of the pre processor directive , we also have #include followed by the file name

The c pre processor makes the program more user friendly and readable

The following example will make it more clear

#include<stdio.h> // #include pre processor

#define PI 3.14 // #define preprocessor

main()

{

float radius = 4;

float area;

area = PI * (radius * radius);

printf(" area is %f \n",area);

getch();

}

Array

2012-07-30T03:54:00.000-07:00

Array is a variable that represents a collection of identical objects , that means we can store a group of variables of same data type and name together

Do you remember the strings , yes that was a character array , but now we will see integer array

Each member of an array is referred by a index value starting with 0 and the last element of a array is an null character that is \0

The above figure shows a array of elements of size 20 , but remember that since the last position is occupied by a null character so the actual size of the array is 19

As said we can have array of integers or array of characters also called strings

Syntax for array is

Data_type array_name [size of array];

We can accept values for every array element one by one but that is not how it is done , instead we use a loop (for loop ) to enter and to print the values of an array , but it is possible to do one by one if needed

main()

{

int array[5];

int i;

for(i=0;i<5;i++)

{

printf("Enter number fo position %d \n",i+1);

scanf("%d",&array[i]);

}

for(i=0;i<5;i++)

{

printf(" Array Element in %d is ..... %d\n",i+1,array[i]);

}

getch();

The above program accepts values for the array “int arrya” , loops it in a for loop that runs from 0 to 4 and in each time changes the index of the array “array[i]” to save the values at different positions and in the next for loop prints the array elements one by one

Multi dimensional Array

Sine now we were only seeing array that can store values like the compartments of a train each one having one value but now we will see multi dimensional array , think it of like a stack of train on one another

So multidimensional array looks like

Data_type array_name [column size] [row size];

So if we have an array of [2][20]

It will look like this

We can use these kind of array to form a grid but for now let us print time table from 1 to 10 using multi dimensional array and for loop

main()

{

int i,j;

int array[10][10];

for(i=0;i<10;i++)

{

for(j=0;j<10;j++)

{

array[i][j] = (i+1)*(j+1);

}

for(i=0;i<10;i++)

{

for(j=0;j<10;j++)

{

printf("%3d ",array[i][j]);

}

printf("\n");

}

getch();

}

This programs just display the times table from 1 to 20

Loops

2012-07-30T03:53:00.003-07:00

Loops are one of the most important part in c programming , loops are a piece of coding that repeats itself again and again until a condition or a terminating condition is meet , there are different kinds of loops and we will look at each of them

In order to better understand loops let us take an example and see how we can use different loops to solve it

So let us consider that we want to find the sum of all the number from 1 to 100 in a program , In this type of condition we use loop

While Loop

The syntax of while loop is like

While ( condition )

{

Coding

}

So to better understand this let us look an example of finding the sum of 1 to 100

main()

{

int total = 0;

int counter = 1;

while(counter <= 100)

{

total = total + counter;

counter = counter + 1;

}

printf("%d",total);

getch();

}

So as you can see in the program the coding inside the while loop will continue until the value of counter becomes 100 , that means the loop will run for 100 times and within this time total will be incremented to find the sum of all the number from 1 to 100

How about writing the multiplication table of two

main()

{

int num =2;

int total = 0;

int counter = 0;

int val ;

while(counter < 10)

{

counter = counter +1;

val = num * counter;

printf("%d * %d = %d\n",num,counter,val);

}

getch();

}

These are some of the thing we can do with loop , but there are many more

For Loop

For loop is another kind of loop , its syntax is different from while loop but we can do almost the same thing with for loop also

for( initialization ; condition ; increment )

{

}

Initialization is much like declaration , here we define the starting point , the condition defines the ending point and increment defines how we will go from initial point to end , the following example will make more sense

Lets do the above examples using for loop

main()

{

int total = 0;

int counter = 1;

int i;

for(i = 1 ; i<=50 ; i++)

{

total = total + i;

}

printf("%d\n\n",total);

getch();

}

above program also finds the sum of numbers from 1 to 50

now let us do the multiplication table of 2 in for loop

main()

{

int total = 0;

int counter = 1;

int I , j = 2;

for(i = 1 ; i<=10 ; i++)

{

total = j * i;

printf("\n%d * %d = %d\n",j,i,total);

}

getch();

}

We have made a program to display multiplication table of two using for loop

Do while Loop

Do while loop is like while loop but the difference is that the code inside the do while loop execute once even if the condition is not meet

The syntax for do while loop is

{

}

while (condition );

the sum of 1 to 100 with do while loop looks like this

main()

{

int total = 0;

int counter = 1;

do {

total = total + counter;

counter = counter + 1;

}while(counter <= 100);

printf("%d",total);

getch();

}

Logical operators

2012-07-30T03:52:00.004-07:00

These operators provide logic to our programming , there are basically 3 types of logical operator

And operator	&&
Or operator	\|\|
Not operator	!

We use logical operators with other operators in order to make our programming more efficient

Now to better understand this let us make a program that’s takes a number called marks as input and display the result based on following conditions

0 to 30 ---------- D

31 to 40 ------- C

41 to 50 --------B

51 to 70 --------A

71 to 100 ------ A+

So our program will look like

main()

{

int marks;

printf("Pl enter your marks\n");

scanf("%d",&marks);

if((marks >=71) && (marks <=100))

{

printf("A+");

}

else if((marks >=51)&&(marks <=70))

{

printf("A");

}

else if((marks >=41)&&(marks <=50))

{

printf("B");

}

else if((marks >=31)&&(marks <=40))

{

printf("C");

}

else if((marks >= 0)&&(marks <=30))

{

printf("D");

}

else

{

printf("invalid");

}

getch();

}

We can have combinations of "and , or , not" to have many results

Or and “and” have same syntax with different symbols but not is slightly different , for example if we have to check if a value is not some value then we write

if(!(variable == value));

Relational operators and Selection Statement

2012-07-30T03:51:00.003-07:00

Relational operators are operators which we use to evaluate two or more statements , like weather statement A is equal to statement B and so on , different relational operators are

= =	Equal to operator
! =	Not equal to operator
>	Greater than operator
<	Less than operator
>=	Greater than equal to
<=	Less than equal to

These are our basic relational operator . But these operator does not work alone , they are used with other operators in order to get some output and these are called selection statements .

Selection statements and relational operators have to work side by side in order to get result , so let us see what are selection statements and how we use relational operators with them

Selection Statements

These are used in a program to make logical decision which is the heart of programming language , so let us see different selection statement with working examples

If statement – in order to understand if statement let us consider a example , suppose you have a

variable that stores age of a person and you want that if the age is above 80 you display a special message , so how you are going to do it , we do it with if statement and relational operator ,

The syntax for if statement looks like

if (condition)

{

}

So our above example will look like

If ( age > 80)

{

printf(“ Welcome sir ! you have made a long way “);

}

That is how if statement works , now if you want to display another message for those whose age is not 80 , we do it with if else statement , like this

If ( age > 80)

{

printf(“ Welcome sir ! you have made a long way “);

}

else

{

printf(“ Welcome sir”);

}

this is how we use if else statement , now imagine a situation in which we want to display multiple message based on multiple conditions , so in this situation we use else if statement like this

If ( age > 80)

{

printf(“ Welcome sir ! you have made a long way “);

}

else if(age >70)

{

printf(“ Welcome sir”);

}

else if(age >50)

{

printf(“good day”);

}

else if(age > 30)

{

printf(“hello”);

}

else

{

printf(“hi”);

}

This is how we use the if statement , we can use the if statement with all the relational operators to get the output

In order to understand the if statement let us make a program to accept a single number from the user from 0 to 9 and display a quote for each number

main()

{

int number;

printf("Please enter a number between 0 to 9\n");

scanf("%d",&number);

if(number == 0)

{

printf("I like the dreams of the future better than the history of the past");

}

else if(number == 1)

{

printf("You cannot dream yourself into a character: you must hammer and forge yourself

into one");

}

else if(number == 2)

{

printf("Commitment leads to action. Action brings your dream closer");

}

else if(number == 3)

{

printf("To unpathed waters, undreamed shores.");

}

else if(number == 4)

{

printf("Hope is the dream of the waking man");

}

else if(number == 5)

{

printf("The best way to make your dreams come true is to wake up.");

}

else if(number == 6)

{

printf("The future belongs to those who believe in the beauty of their dreams");

}

else if(number == 7)

{

printf("Imagination is more important than knowledge.");

}

else if(number == 8)

{

printf("Your imagination is your preview of life's coming attractions");

}

else

{

printf("Believe that you have it, and you have it");

}

getch();

}

This is a very simple program , just type a digit and it will display a message corresponding to the digit

Switch Statement

As we can see if statement can be very useful but switch is another selection statement that is widely used , unlike if statement switch statement only compare a single value with a multiple conditions , the switch syntax is

switch(integer_expression)

{

Case 1: printf(“statement “);

Break;

Case 2: printf(“statement “);

Break;

Case 3: printf(“statement “);

Break;

default: printf(“statement”);

}

Switch statement does not accept conditions or comparisons , it takes a value and evaluates according to the cases , we add a break; because if the required case is obtained then the program comes out of the structure saving resources , So the above example on quotes can be re-written as

main()

{

int number;

printf("Please enter a number between 0 to 9\n");

scanf("%d",&number);

switch(number)

{

case 0:

printf("I like the dreams of the future better than the history of the past");

case 1:

printf("You cannot dream yourself into a character: you must hammer and forge yourself into one");

break;

case 2:

printf("Commitment leads to action. Action brings your dream closer");

break;

case 3:

printf("To unpathed waters, undreamed shores.");

break;

case 4:

printf("Hope is the dream of the waking man");

break;

case 5:

printf("The best way to make your dreams come true is to wake up.");

break;

case 6:

printf("The future belongs to those who believe in the beauty of their dreams");

break;

case 7:

printf("Imagination is more important than knowledge.");

break;

case 8:

printf("Your imagination is your preview of life's coming attractions");

break;

default:

printf("Believe that you have it, and you have it");

}

getch();

}

This program also does the same thing , just type a digit and it will display a message corresponding to the digit

Arithmetic operators

2012-07-30T03:50:00.003-07:00

In order to perform some basic calculation we need these arithmetic operators , these are nothing but our old arithmetic operations like addition , subtraction , multiplication and division , there is not much to say about them , so let see some examples to make it clear

main()

{

int a , b; //we can declare multiple variable at a same time like this

int add,sub,mul,div;