C Programming Online

C Programming Tutorials : printf Format String

noreply@blogger.com (Anonymous) — Tue, 12 Mar 2013 14:08:00 +0000

This post describes the use of Format String or Control String in printf function. An example of printf function is :
printf(" [FORMAT_STRING/CONTROL_STRING] ", arg1, arg2, ... );

Basic Structure of Format String or Control String in printf() Function:

% [FLAG] [WIDTH] . [PRECISION] [MODIFIER] [TYPE]

[FLAG]

- (minus)

Output is left-adjusted within the field. Remaining field will be blank.

If no used, output is right-adjusted within the field.

Works with: char, int , float, double, string.

+ (plus)

The sign of the numeric will be added before the numeric value i.e. if the numric value is positive, then a + sign will be added before the value.

Works with: int, float, double
Prints nothing with: char, string

0 (zero)

Causes leading zeros to appear.

Works with: string, int, float, double.
Prints nothing with: char

(with o or x)

Causes octal and hex items to be preceded by 0 (zero) and 0x , respectively.

Works with:

( Octal )	%#o
( Hex )	%#x or %#X

(with e, f or g)

Causes decimal point to be present in all floating point numbers.
Prevents the truncation of trailing zeros in g-type conversion.

Note: FLAGS can be mixed in any order

[WIDTH]

It is a +ve integer. It defines minimum field width.

Case 1: Length of data < [WIDTH]
=> Data is printed right-adjusted

Case 2: Length of data >= [WIDTH]
=> Entire data gets printed.

Note: If the [WIDTH] is given as -ve, then the - (minus) sign will be treated as flag

[PRECISION]

with String	Indicates no of charecters to be printed . If [PRECISION] > Length of data, entire String gets printed
with float, double and long double	Indicates no. of digits to be printed after decimal point. If [PRECISION] < no. of digits after decimal point, rounded value will be printed. If [PRECISION] > no. of digits after decimal point, trailing zeros will be added.
with integer	If [PRECISION] > Length of data, prints (precision - length of data) no. of zeros.
with char	Does nothing

Note: [PRECISION] is a positive integer. If it is given as negative, then - (minus) sign + precision value + type gets printed.

[MODIFIERS]

h	for short integer
l	for long integers or double
L	for long double

[TYPE]

%a	Hexadecimal output in the form 0x h.hhhhhh p+ or - xxxx (C99 only)
%A	Hexadecimal output in the form 0x h.hhhhhh P+ or - xxxx (C99 only)
%x	Hexadecimal integer e.g. 0x5fc8
%X	Hexadecimal integer e.g. 0x5FC8
%o	Octal integer e.g. 0879
%c	type char e.g. 'a', 'A', '8' etc.
%d	decimal integer (signed ) e.g. 5, -4 etc.
%i	decimal integer (signed ) e.g. 6, -6 etc.
%u	unsigned decimal integer etc. 5, 6 etc.
%s	String e.g. "Do you like this article?" etc.
%e	scientific notation in the form d.xxxxxx e + or - xxx
%E	scientific notation in the form d.xxxxxx E + or - xxx
%f	float in the form d.xxxxxx e.g. 5.000000
%g	uses %e or %f whichever is shorter e.g. 100000, 1e+006, 0.0005, 5e-005 etc.
%G	uses %E or %f whichever is shorter
%p	Segment address (of pointer variable) in Hex. e.g. 12ao
%Fp	Segment address and offset address in Hex. e.g. 0001:00f2
%n	The associated argument must be a pointer to an integer. This specifier causes the number of charecters written (upto the point at which %n is entercounted) to be stored in that integer.
%%	prints a % sign

Note: [WIDTH] and [PRECISION] can be specified as a argument variable in printf() function. For example,
printf( "%*.*s" , width, precision );

Few Examples of printf() Function

Assume, the following variable declarations:
char str[]="world";
int a = 50;
int b = -50;
float c = 4.5446;
unsigned int d = 5;

Note: The following examples are Tested on 32 bit GCC compiler

Statements	Output
printf("%s", str); printf("%-10s",str); printf("%2s",str); printf("%-2s",str); printf("%(-10)s",str); printf("%-(-10)s",str); printf("%20(-10)s",str); printf("%5s",str); printf("%-5s",str); printf("%+10s",str); printf("%010s",str);	world world world world (-10)s (-10)s (-10)s world world world 00000world
printf("%-10d",a); printf("%+-10d",a); printf("%010d",a); printf("%0+10d",a); printf("%+0+10d",a); printf("%010d",b); printf("%#d",a); printf("%#x %x",a,a); printf("%#o %o",a,a); printf("%f",6); printf("%f",6.); printf("%f",6.0); printf("%f"); printf("%d");	50 +50 0000000050 +000000050 +000000050 -000000050 50 0x32 32 062 62 0.000000 6.000000 6.000000 0.000000 garbage value
printf("%10.2s",str); printf("%10.8s",str); printf("%10.-4s",str); printf("%1.-4s",str); printf("%10.5f",c); printf("%10.3f",c); printf("%10.9f",c); printf("%.5f",c); printf("%4.3d",a); printf("%.0d",a); printf("%d %d", 5, -5); printf("%i %i", 6, -6); printf("%u %u", 7, -7); printf("%5.3c",'d'); printf("%0c",'d'); printf("%I64"); printf("%s","Hello"); printf("%s","%d",5); printf("I64d",5); printf("%I64d",-5); printf("%d"+1,5);	wo world -4s -4s 4.54460 4.545 4.54600000 4.54460 050 50 5 -5 6 -6 7 4294967289 d d prints nothing Hello %d 21474836485 25769803771 d

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Online C Programming Test

noreply@blogger.com (Anonymous) — Tue, 04 Sep 2012 19:13:00 +0000

Test Description

Subject = C Programming
No of Questions = 20
Time = 30 mins
Total Marks = 20

Correct Answer = 1 mark
Wrong Answer = - 0.25 mark (negative)

C Program to find Armstrong Number

noreply@blogger.com (Anonymous) — Tue, 04 Sep 2012 10:05:00 +0000

Definition of Armstrong Number:
A number is Armstrong if the sum of cubes of individual digits of a number is equal to the number itself.

Example:
0, 1, 153, 370, 371, 407 etc.

Explanation:
Let us take 153.

So, the sum of cubes of individual digits

= 1^{3 +}5^{3 +}3³

= 1 + 125 + 27

= 153

Programming Approach (Algorithm):

Step 1: number = <Entered Number>

Step 2: Right Most Digit = number % 10

Step 3: number = number / 10

Step 4: Sum = Sum + Cube of Right Most Digit

Step 5: Repeat Step 2, 3 & 4 until number = 0

Step 6: if Sum = <Entered Number> then return 1

// <Entered Number> is Armstrong number

else return 0 // <Entered Number> is not an Armstrong number

C Program:

/*
* PROGRAM NAME: Armstrong Number
* SOURCE: http://CProgrammingOnline.blogspot.com
*/

/* HEADER FILE DECLARATION SECTION */
#include<stdio.h>

/* FUNCTION PROTOTYPE DECLARATION SECTION */
_Bool armstrong(int );

/* MAIN PROGRAM SECTION */
int main(char* argv[], int argc){
int number; //Used to store the given number

printf("\nProgram to Test Whether a Number is Armstrong Number or Not\n");
printf("Enter an Integer Value (Max Size = %d bytes): ",sizeof(int));
scanf("%d",&number);

if(armstrong(number)==1){
printf("\n%d is an armstrong number.",number);
} else {
printf("\n%d is not an armstrong number.",number);
}
}

/*
* FUNCTION SIGNATURE: _Bool armstrong(int );
* INPUT: int number
* OUTPUT: 1 if number(INPUT) is an armstrong number
* 0 if number(INPUT) is not an armstrong number
*/
_Bool armstrong(int number){
int stored_number = number; //Used to Store the given number
int sum = 0; //Used to Store the sum of digits
char digit; //Used to Store the digits

while(stored_number > 0){
digit = stored_number % 10;
sum += digit * digit * digit;
stored_number /= 10;
}

if(sum == number){
return 1;
} else {
return 0;
}
}

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Copy Text File using C Program

noreply@blogger.com (Anonymous) — Sat, 04 Aug 2012 06:14:00 +0000

#include<stdio.h>

int main(int argc, char* argv[]){
FILE *sfp; // Source File Pointer
FILE *tfp; // Target File Pointer
char SourceFilename[255]; // Stores the source file name
char TargetFilename[255]; // stores the target file name
char ch; // used to read charecter
// from source file name

/* Get sourcefile name and targetfile name from the user */
printf("\nEnter Soucefile Name: ");
gets(SourceFilename);
fflush(stdin);
printf("Enter Targetfile Name (NOTE : If Targetfile already exists, its content will be overwritten): ");
gets(TargetFilename);

/* Open source file in read mode and target file in write mode */
sfp=fopen(SourceFilename,"r");
if(sfp==NULL){
printf("\nERROR: Failed to open %s in read mode. Closing the program...",SourceFilename);
return;
}
tfp=fopen(TargetFilename,"w");
if(tfp==NULL){
printf("\nERROR: Failed to open %s in write mode. Closing the program...",TargetFilename);
return;
}

/* read charecter by charecter from sourcefile
and write those charecters accordingly in targetfile */
while(1){
ch=fgetc(sfp);
if(ch==EOF){
break;
}else{
fputc(ch,tfp);
}
}

/* close file pointers */
fclose(sfp);
fclose(tfp);
}