PROGRAMMING LANGUAGE BASIC - Leo Tutorials

                                        PROGRAMMING LANGUAGE 
The functioning of a computer is controlled by a set of instructions ( called a computer program ). These instruction are written to tell the computer:
         What operation to perform?
         Where to locate data?
         How to present results?
         When to make certain decisions? and so on.
        The communication between two parties whether they are machines or human beings always needs a common language or terminology. The language used in the communication of computer instructions is known as the programming language.The computer has its own language and any communication with the computer must be in its language or translated into this language.
Three levels of programming language are available. They are:

  1. Machine language (low level language)
  2. Assembly (or symbolic) language, and 
  3. Procedure-oriented language (high level language)
MACHINE LANGUAGE 

Computer are made of two-state electronic components which can understand only pulse and no-pulse (or '1' and '0' ) conditions. Therefore, all instructions and data should be written using binary codes 1 and 0. The binary code is called the machine code or machine language.
       Computer do not understand English, Hindi, or Tamil. They respond only machine language. Added to this, computers are not identical in design. Therefore, each computer has its own machine language. (However, the script, 1 and 0, is the same for all computers.) This poses two problems for the user.
       First, it is a traumatic experience to understand and remember the various  combinations of 1's and 0's representing numerous data and instructions . also, writing error-free instructions is a slow process.
       Secondly, since every machine has its own machine language, the user cannot communicate with other computers (if he does not know its language). Imagine a Tamilian making his first trip to Delhi. He would face enormous obstacles as soon as he moved out for shopping. A Language barrier would prevent hi, from communicating.



ASSEMBLY LANGUAGE 

An assembly language uses mnemonic codes rather than numeric codes (as used in machine language). For example,ADD or A is used as a symbolic operation code to represent addition and SUB or S is used for subtraction. Memory locations containing data are given names such as TOTAL, MARKS,TIME,MONTH,etc.
         As the computer understands only machine-code instructions, a program written in assembly language must be translated into machine language before the program is executed. This translation is done by a computer program referred to as assembler.
        The assembly language is again a machine-oriented language and hence the program has to be different for different machines. The programmer should remember machine characteristics when he prepares a program. Writing a program is assembly in assembly language is still a slow and tedious task.

PROCEDURE-ORIENTED LANGUAGE (POL)

These languages consist of a set of words and symbols and one can write program using these in conjunction with certain rules like 'English' language. These languages are oriented toward the problem to be solved or procedures for solution rather than mere computer instructions. These are more user-centered than the machine-centered languages. They are better known as high-level languages.
       The most important characteristics of a high-level language is that it is machine-independent and a program written in a high-level language can be run on computers of different makes with little or no modification. The programmer need not know the characteristics of that machine.However,such programs are to be translated into equivalent machine-code instruction before actual implementation.
       A program written in a high-level language is known as the source-program and can be run on different machines using different translators. The translated program is called the object program.

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