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November 14, 2017

IBPS Specialist (IT) Officers Professional Knowledge Study Material - Programming Languages

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Programming Language

A programming language consists of words, symbols and usage rules pertaining to the grammar that permits people to communicate with the computer. Understanding of computer software is imperfect without a basic knowledge of programming languages. Programming languages allow the programmers and end users to develop the programmes that are executed by the computer. Many programming languages exist in the world today. Each one of the languages have their own unique vocabulary, grammar and usage. Some of these languages have been created to serve a special purpose while others are more flexible and general purpose and are suitable for many types of applications. However in general, programming languages must cater to the following tasks : 
  • input/ output
  • text manipulations/ calculations 
  • logic/ comparison 
  • storage/ retrieval 

CLASSIFICATION OF PROGRAMMING LANGUAGES

Machine Languages : Machine language is the lowest form of computer language. Programmes  were only written in binary based machine level language in the first generation computers. The computer understands this language only at its lowest level. 

An instruction perpared in machine language has two parts :
  1. Op-code : This is the first part and is the command or operation and it tells the computer what function to perform.
  2. Operand : The second part of the instruction is the operand and it tells the computer where to find or store the data or instructions that are to be manipulated. The number of operands in an instruction varies from computer to computer. In a single operand machine, the binary equivalent of "ADD0481" could cause the value in a storage location 0481 to be added to a value stored in the arithmetic & logic unit. The single operand format is popular in the smallest microcomputers whereas the two operand structure is found in most other machines. 
The set of instructions in a machine level language can be divided into four categories :
  1. Arithmetic — add, subtract, multiply and divide 
  2. Control — load, store, jump instructions 
  3. Input output — Read and write 
  4. Direct use — Halt, start and end
No arithmetic or comparison operations are done in the primary memory of the computer. Instead it is done in the ALU's special register called accumulator. Thus if we need to add two numbers, we require one instruction which will order the control unit to place a nuber in the accumulator and another instruction to identify the operation of addition.

Symbolic / Assembly Languages : In order to reduce the burden, symbolic languages, commonly known as assembly languages were developed in 1950's for the second generation computers.

Assembly language permits the use of symbols or mnemonics which are two or three letter abbreviations for the function to be performed by the instruction. These are then translated by using symbolic equivalence table, to control registers etc. So, the disadvantage of using binary language has been removed. 

Functions of Assembler
  • The Assembler translates the function code into its machine code equivalent. 
  • It assigns absolute addresses to any symbolic address or label names. 
  • It places each instruction in central memory. 
  • It identifies indirect addresses from direct addresses and sets the appropriate bit in the address portion of the instruction. 
  • It checks the syntax of each instruction and generates error messages. 
  • It provides, optionally, a cross reference table between all symbolic names and their absolute addresses. 
  • It informs the control unit to exceute the program after all errors have been corrected.
Advantages of Assembly languages
  • They save time and reduce detail as compared to machine language. 
  • Lesser number of errors are made and errors are easier to detect.
  • Assembly programs are easier to modify than machine language programs
Disadvantages of Assembly Language
  • Writing a code is time consuming.
  • Assembly languages are machine dependent.
HIGH LEVEL LANGUAGES

The disadvantages of using assembly language brought about the development of higher level languages. Unlike the assembly programs, high level language programs may be used different types of machines with little modification. High level languages are easier to learn than symbolic languages. They require less time to write, are easier to maintain, provide better documentation and 4 or 5 low- level instructions are reduced to a single high level statement. Being from IT, all of us know the high level languages like C, C++ and Java. Here are some more popular high level languages. 


Language
Meaning
Main Application Area
FORTRAN
Formula Translator
Scientific & Engineering
COBOL
Common Business Oriented Language
Commercial
ALGOL
Algorithmic Language
Scientific
RPG
Report Generator
Commercial
APL
A Programming Language
The Sharing System
PL / 1
Programming Language
The Sharing System
BASIC
Beginners All Symbolic Instruction Code
Teaching
PASCAL
Named after the French Philosopher
Teaching

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