Computer program

Computer programs may be categorized along functional lines: system software and application software. Two or more computer programs may run simultaneously on one computer, a process known as multitasking.

Computer Languages

A computer program (also a software program, or just a program) is a sequence of instructions written to perform a specified task for a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute the instructions. The same program in its human-readable source code form, from whichexecutable programs are derived (e.g., compiled), enables a programmer to study and develop its algorithms.

Computer source code is often written by computer programmers. Source code is written in a programming language that usually follows one of two main paradigms: imperative or declarative programming. Source code may be converted into an executable file (sometimes called an executable program or a binary) by a compiler and later executed by a central processing unit. Alternatively, computer programs may be executed with the aid of aninterpreter, or may be embedded directly into hardware.

A programming language is an artificial language designed to express computations that can be performed by a machine, particularly a computer. Programming languages can be used to createprograms that control the behavior of a machine, to express algorithms precisely, or as a mode of human communication.

The earliest programming languages predate the invention of the computer, and were used to direct the behavior of machines such as Jacquard looms and player pianos. Thousands of different programming languages have been created, mainly in the computer field, with many more being created every year. Most programming languages describe computation in an imperative style, i.e., as a sequence of commands, although some languages, such as those that support functional programming or logic programming, use alternative forms of description.

A programming language is usually split into the two components of syntax (form) and semantics (meaning) and many programming languages have some kind of written specification of their syntax and/or semantics. Some languages are defined by a specification document, for example, the C programming language is specified by an ISO Standard, while other languages, such asPerl, have a dominant implementation that is used as a reference.

Generation of Programming Languages

1. The first generation languages, or 1GL are low-level languages that are machine language.
2. The second generation languages, or 2GL are also low-level languages that generally consist of assembly languages.
3. The third generation languages, or 3GL are high-level languages such as C.
4. The fourth generation languages, or 4GL are languages that consist of statements similar to statements in a human language. Fourth generation languages are commonly used in database programming and scripts.
5. The fifth generation languages, or 5GL are programming languages that contain visual tools to help develop a program. A good example of a fifth generation language is Visual Basic.