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Introduction
A language usually consists of all the verbal or written symbols, grammatical rules and
expressions that are used to exchange ideas and information. Communications can take place
between individuals or between an individual and a computer. The two BASIC types of
languages used in computers are low-level language and high-level languages. Low-level
languages are again subdivided into machine and assembly languages. High-level languages
may be general purpose or special purpose. They may be either compiler based or interpreter
based. High-level languages look similar to our English language and hence are better
understood by the programmers rather than the computers. Low-level languages are compatible
with the hardware of the computer and consist of binary or mnemonic codes. Hence, low-level
languages are understood by the computers in a better manner. It is difficult for the programmer
to understand the low level language.
Machine language
The lowest form of computer language is machine language. In the first generation computers,
programs were written only in binary based machine level languages. It has to be remembered
that the only language that is understood by the computer is the machine language. However,
almost all the programs that are written today are in high level languages. Since computers can
understand only machine language, these programs (written in higher level languages) are
translated to machine level languages using a software program called compiler/interpreter.
Machine language is the most BASIC form of programming and hence explicit instructions are
to be given to the machine to perform each operation. Hence, it is necessary to tell the machine
where to store numbers in its memory and how to add the numbers and so on. A statement of the
form P = Q + R is meaningless in a machine code. If you want to add Q with R, then you have to
instruct the machine exactly how to transfer and process the numbers, where to store the result P,
etc.
Any set of instructions in a machine level language can be divided into the following four
categories: Arithmetic, control, input-output and direct use. The functions of these statements are
as follows:
Arithmetic : Add, subtract, multiply and divide
Control : Load, store and jump
Input-output : Read and write
Direct use : Start, halt and end
The arithmetical operations or comparisons are done in the arithmetic logic unit with the use of
accumulators. Hence, if you want to add two numbers together, we will need one instruction
which will order the control unit to place a number in an accumulator and another
instruction to identify the addition operation. Machine language instructions are represented by
binary numbers, i.e.,sequences consisting of 0s and 1s. For example, the binary sequence.
001010011010 could represent a 12 bit machine language instruction. The instruction is
divided into two parts: operation code (or Op code) and an operand.Op code Operand
0010 10011010
The Op code specifies the operations such as add, multiply, etc. and the operand is the address of
the data item that is to be operated upon. Thus, while using a machine language, we have to
remember the code numbers for the operations and also keep track of the addresses of all the
data items. Hence, machine language is highly complicated and complex and subject to error.
Also, the programs written in machine language are machine dependent. That means, a program
that has been developed for a particular machine cannot be run on another machine. It is clearly
