COMPUTER PROGRAMMING

Computer Programming

Computer Programming

Programming Language

A programming language is a set of characters, rules for combining them, and rules specifying their effects when executed by a computer, which have the following four characteristics:

It requires no knowledge of machine code on the part of the user. In other words, the user needs only learn the particular programming language, and can use this quite independently of (perhaps nonexistent) knowledge of any particular machine code. This does not mean that the user can completely ignore the actual computer. For example, the user may need to know how floating-point numbers are represented, or may wish to take advantage of certain known machine resources which provide more efficient programs. In particular, the user obviously cannot use input-output equipment that does not exist on a particular computer configuration. However, the fundamental point is that a knowledge of the basic machine code for the given computer is not needed.

A programming language must have some significant amount of machine independence. This means that there must be some high potential of having a source program (a program written in a high-level language) run on two computers with different machine codes without major rewriting of the source program. (Although complete machine independence is an ideal that is often approximated rather than achieved, it is now increasingly common to move programs from one computer to another with little or no change.)

When a source program is translated into machine language, there is normally more than one machine instruction per executable unit created. For example, an executable unit in a programming language might be something of the form “A : = B + C * D” or “OPEN FILE ALPHA.” Normally, each of these executable units would be translated into more than one machine instruction.

A programming language employs a notation that is closer to that of the specific problem being solved than is machine code. Thus, for example, the example “A: = B + C * D” might be translated into a sequence of machine instructions such as which is clearly less understandable than the programming language form.

CLA C

MPY D

ADD B

STO A

To teach a computer to solve that problem and how he way he should do so, one needs a method to communicate with the computer. People generally use a language as a means of communication. Even computers, speak a language ``. However, it is considerably simpler than the language of the people. Thus, the native language of the computer consists of an alphabet that contains only the two characters, 0 and ``, 1 ``. Based on this, the words of the computer language with a circumference of a few tens up to a maximum of a few hundred made. In contrast, includes the contemporary German language has a vocabulary of about hundred and twenty thousand words. In principle, satisfy the two characters of the alphabet, the computer language, for all that is in principle expressible in some language to express. This would arise, however, very long and for the people no longer directly ...