Programming is a practice of making a set of instructions which serves for useful purpose. It is instructing a computer to do something for someone and is used to write instructions in a specific format. It allows certain data manipulations to be expressed with a set of symbols. Programming languages allow us to 'speak' to the computer at a level that is closer to how humans think than how computers 'think'.
The role of a programming language can be described in two ways:
Technical: It is a means for instructing a Computer to perform Tasks
Conceptual: It is a framework within which we organize our ideas about things and processes.
According to the last statement, in programming we deal with two kind of things:
data, representing ``objects'' we want to manipulate
procedures, i.e. ``descriptions'' or ``rules'' that define how to manipulate data.
According to Abelson and Sussman,
``.....we should pay particular attention to the means that the language provides for combining simple ideas to form more complex ideas. Every language has three mechanisms for accomplishing this: primitive expressions, which represent the simplest entities with which the language is concerned
means of combination, by which compound expressions are built from simple ones, and
means of abstraction, by which compound objects can be named and manipulated as units.''
A programming language should both provide means to describe primitive data & procedures and means to combine & abstract those into more complex ones. With the passage of time, a number of programming languages evolved, some of which are - Basic, Fortran, C, C++, Java, Delphi, VB, VC++, C# etc. Each of them has its own characteristics. The instructions written in a programming language are referred to as a program. A computer program is simply a set of instructions to tell a computer how to perform a particular task. Basically a programmer writes a program in a high level language which is interpreted into the bytes that the computer understands. In technical speak the programmer generates source code and the interpreter generates object code. Sometimes object code has other names like: P-Code, binary code or machine code.
The interpreter has a couple of names, one being the interpreter and the other being the compiler. These terms actually refer to two different techniques of generating object code from source code. It used to be the case that compilers produced object code that could be run on its own (an executable file - another term) whereas an interpreter had to be present to run its program as it went along. The difference between these terms is now blurring however since some compilers now require interpreters to be present to do a final conversion and some interpreters simply compile their source code into temporary object code and then execute it.
