Programmer's Den

Programming - What's the fuss all about...

2008-04-16T08:44:00.000-07:00

Computer Programming - is simply writing down instructions for the computer to follow. For stating the instructions, we need some language in which to state the instructions. Unfortunately, natural languages such as English are insufficiently precise for giving instructions to computers. Instead, we use special purpose languages called programming languages.Thus programing can be defined as the process of writing, testing, debugging/troubleshooting, and maintaining the source code of computer programs. The code may be a modification of an existing source or something completely new. The purpose of programming is to create a program that exhibits a certain desired behavior (customization). The process of writing source codes requires expertise in many different subjects, including knowledge of the application domain, specialized algorithms & formal logic.

What is Algorithm?

An algorithm is a set of instructions for carrying out a particular task. ( The task does not necessarily has to be related to programming, although the word algorithm is usually used in terms of programming.) Unlike a program, which must be expressed in a form suitable for processing by a computer, an algorithm can be expressed in whatever form is convenient for a person to understand. Every correct algorithm comes with a guarantee that, if followed the instructions correctly, the particular task will be accomplished. For an algorithm to live up to the guarantee, every algorithm must have the following characteristics:

An algorithm must be precise. Each step in an algorithm must state unambiguosly what action is to be taken.
An algorithm must be effective. It must be possible to actually carry out every step of the algorithm.
An algorithm must have a fixed, finite number of instructions.
The execution of the algorithm must always terminate .

Different programming languages support different styles of programming (called Programming Paradigms). The choice of language used is subject to many considerations, such as company policy, suitability to task, availability of third-party packages, or individual preference.

Programming Paradigms:

A programming paradigm is a fundamental style of computer programming. Different programming languages adovate different programming paradigms. Some languages are designed to support one particular paradigm (Smalltalk supports object-oriented programming, Haskell supports functional programming), while other programming languages support multiple paradigms (such as Object Pascal, C++, C#, Visual Basic, Common Lisp, Scheme, Python, Ruby & Oz).

For more information on types of programming paradgims, visit : http://en.wikipedia.org/wiki/Programming_paradigm

Next : Types of Programming Languages.

Types of Programming Languages

2008-04-16T08:33:00.000-07:00

Programing Languages can be classified into basic 3 categories.

Machine Level Language
High Level Language
Assembly Language

Machine Level Language:

Machine Level Language ( A.K.A - Lower Level Language) - instructions are written as sequences of 1s and 0s, called bits, that a computer can understand directly.
An instruction in machine language generally tells the computer four things:

Where to find one or two numbers or simple pieces of data in the main computer memory (Random Access Memory, or RAM).
A simple operation to perform, such as adding the two numbers together.
Where in the main memory to put the result of this simple operation.
Where to find the next instruction to perform.

While all executable programs are eventually read by the computer in machine language, they are not all programmed in machine language. It is extremely difficult to program directly in machine language because the instructions are sequences of 1s and 0s. A typical instruction in a machine language might read 10010 1100 1011 and mean add the contents of storage register A to the contents of storage register B.

According to the Utah State Office of Education, a low level language is one that does not need a compiler or interpreter to run. The processor in which the language was written for would be able to run the code without the use of either of these. These type of programming languages are sometimes described as being "close to the hardware."

These type of languages fall under the 1st Generation Language (1GL).

Assembly Language:

An assembly language is a low-level language for programming computers. It implements a symbolic representation of the numeric machine codes and other constants needed to program a particular CPU architecture. This representation is usually defined by the hardware manufacturer, and is based on abbreviations (called mnemonics) that help the programmer remember individual instructions, registers, etc. An assembly language is thus specific to a certain physical or virtual computer architecture (as opposed to most high-level languages, which are portable). Computer programmers use assembly languages to make machine-language programs easier to write.

In an assembly language, each statement corresponds roughly to one machine language instruction. An assembly language statement is composed with the aid of easy to remember commands. The command to add the contents of the storage register A to the contents of storage register B might be written ADD B,A in a typical assembly language statement. Assembly languages share certain features with machine languages. For instance, it is possible to manipulate specific bits in both assembly and machine languages. Programmers use assembly languages when it is important to minimize the time it takes to run a program, because the translation from assembly language to machine language is relatively simple. Assembly languages are also used when some part of the computer has to be controlled directly, such as individual dots on a monitor or the flow of individual characters to a printer.

Assembly languages were first developed in the 1950s, when they were referred to as 2nd Generation Language (2GL). They eliminated much of the error-prone and time-consuming 1st generation programming needed with the earliest computers, freeing the programmer from tedium such as remembering numeric codes and calculating addresses. They were once widely used for all sorts of programming.

High Level Language:

High-level languages are relatively sophisticated sets of statements utilizing words and syntax from human language. They are more similar to normal human languages than assembly or machine languages and are therefore easier to use for writing complicated programs. These programming languages allow larger and more complicated programs to be developed faster. However, high-level languages must be translated into machine language by another program called a compiler before a computer can understand them. For this reason, programs written in a high-level language may take longer to execute and use up more memory than programs written in an assembly language.

Some eg. of High Level Languages:Visual Basic, C/C++, Pascal, BASIC etc..

High Level Languages comes under the 3rd Generation Language (3GL).

Back : Introduction
Next : Types of High Level Language

Classification Of High Level Programming Languages

2008-04-16T08:24:00.000-07:00

The High Level Language is basically classified into 3 types namely:

Procedural Language
Functional Language
Object Oriented Language

Procedural Language:

The most common high-level languages today are procedure-oriented languages. In these languages, one or more related blocks of statements that perform some complete function are grouped together into a program module, or procedure, & given a name such as “Procedure A.” If the same sequence of operations is needed elsewhere in the program, a simple statement can be used to refer back to the procedure. In essence, a procedure is just a mini-program. A large program can be constructed by grouping together procedures that perform different tasks.

Procedural languages allow programs to be shorter and easier for the computer to read, but they require the programmer to design each procedure to be general enough to be used in different situations.

Functional Language:

Functional languages treat procedures like mathematical functions and allow them to be processed like any other data in a program. This allows a much higher and more rigorous level of program construction. Functional languages also allow variables—symbols for data that can be specified and changed by the user as the program is running—to be given values only once. This simplifies programming by reducing the need to be concerned with the exact order of statement execution, since a variable does not have to be redeclared, or restated, each time it is used in a program statement. Many of the ideas from functional languages have become key parts of many modern procedural languages.

Object Oriented Language:

Object-oriented languages are outgrowths of functional languages. In object-oriented languages, the code used to write the program and the data processed by the program are grouped together into units called objects. Objects are further grouped into classes, which define the attributes objects must have.

A simple example of a class is the class Book.

Objects within this class might be Novel and Short Story. Objects also have certain functions associated with them, called methods. The computer accesses an object through the use of one of the object’s methods. The method performs some action to the data in the object and returns this value to the computer. Classes of objects can also be further grouped into hierarchies, in which objects of one class can inherit methods from another class. The structure provided in object-oriented languages makes them very useful for complicated programming tasks.

Logic Language:

There's also one more classification called as Logic Language.Logic languages use logic as their mathematical base. A logic program consists of sets of facts and if-then rules, which specify how one set of facts may be deduced from others, for example:If the statement X is true, then the statement Y is false.In the execution of such a program, an input statement can be logically deduced from other statements in the program. Many artificial intelligence programs are written in such languages.

Back : Types of Programming Languages
Next : Language - Structure & Components

Language Structures & Components

2008-04-16T08:11:00.000-07:00

Programming languages use specific types of statements, or instructions, to provide functional structure to the program. A statement in a program is a basic sentence that expresses a simple idea—its purpose is to give the computer a basic instruction. Statements define the types of data allowed, how data are to be manipulated, and the ways that procedures and functions work. Programmers use statements to manipulate common components of programming languages, such as variables and macros (mini-programs within a program).

Statements known as data declarations give names and properties to elements of a program called variables. Variables can be assigned different values within the program. The properties variables can have are called types, and they include such things as what possible values might be saved in the variables, how much numerical accuracy is to be used in the values, and how one variable may represent a collection of simpler values in an organized fashion, such as a table or array. In many programming languages, a key data type is a pointer. Variables that are pointers do not themselves have values; instead, they have information that the computer can use to locate some other variable—that is, they point to another variable.

An expression is a piece of a statement that describes a series of computations to be performed on some of the program’s variables, such as X + Y/Z, in which the variables are X, Y, and Z and the computations are addition and division. An assignment statement assigns a variable a value derived from some expression, while conditional statements specify expressions to be tested and then used to select which other statements should be executed next.

Procedure and function statements define certain blocks of code as procedures or functions that can then be returned to later in the program. These statements also define the kinds of variables and parameters the programmer can choose and the type of value that the code will return when an expression accesses the procedure or function. Many programming languages also permit minitranslation programs called macros. Macros translate segments of code that have been written in a language structure defined by the programmer into statements that the programming language understands.

Back : Types of High Level Languages (3GL)