Computer Language Definition

A language that is acceptable to a computer system is called a computer language or programming language.A computer language consists of all the symbols, characters and rules that permit the user to communicate with the computers.

Computer Languages is broadly classified into the following three categories:

1. Machine Language

2. Assembly Language

3. High Level Language

Machine Language

Machine Language is the language directly understood by a computer without any language translator. Any information or instruction in this language is to be represented in terms of 0’s and 1’s

.A machine language instruction normally has a two-part format

1. First part of an instruction is the operation code, which tells the computer what function to perform.

2.Second part is the operation, which tells the computer where to find or store the data or instructions.

Advantages:
Machine language is directly understood by CPU and it takes shorter time for execution than a program written,There is no need of language translator for execution of machine language.

Disadvantages:
 Machine dependent, Difficult to program,Error prone, Difficult to modify, Non Portable

Assembly Language

A language which allows instructions and storage location to be represented by letters and symbols instead of numbers is called assembly language.

Assembly language is also called symbolic language and it was developed in 1952 to overcome machine language limitations.

In assembly language:- Mnemonic codes are used instead of numeric code instructions.E.g. Add instead of (1110) , Sub instead of (1111),Storage locations to be represented in form of alphanumeric addresses instead of numeric addresses.

Advantages

• Easier to understand and use
•  Easier to locate and correct errors
• Easier to modify
• Human effort required to write a program is much less compared to that needed in writing a machine language program.

Disadvantages

• Assembly language is machine dependent
• Difficult to understand as compare to high level language 
• Programming involves lot of writing.
• Less efficient as compare to machine level language.   

High level language

High level language uses symbols and words that are similar to those of English and ordinary arithmetic. High level language removed the limitation of low level language.

For example C, C++, Java etc.

Advantages:

1.      Machine independent

2.      Easier to learn and understand

3.      Error can be easily removed

4.      Easier to maintain

5.      Coding can be easily done in high level language.

Disadvantages:

1.      Less efficient as compare to machine level language.

2.      Language translator is required for its execution.

4GL

The fourth generation languages are non-procedural languages and hence are highly user friendly.

For easy use most of the 4GL’s are menu driven languages and provide interactive menus. Once the user has made a choice to avail a particular facility to solve a problem, the computer automatically executes a suitable program to deliver the required results.

Language Translator

A translator is a program which converts statements written in one language to statements in another language especially to machine language. There are three types of translators:

1. Assemblers

2. Compilers.

3. Interpreters.

Assembler

It is a program that translates assembly language into machine code. During the process of translation source code (mnemonic code) is converted into its equivalent object code by assembler.

Assembler of two types:

a. Resident Assembler
 An assembler which resides and runs on the same computer for which it is producing object code is called self assembler or resident assembler.

b. Cross Assembler
Cross Assembler run on the computer other than the computer for which it has to         produce the object code.

Compiler

Compiler translates a high level language into machine language. The compiler translates the whole source program into object program prior to the object being loaded into main memory for execution.

Features of Compiler

1.      Difficult to design a Compiler.

2.      Compiler is large program which reside permanently on secondary memory.

3.      Compiler translates the entire program to object code.

4.      Conversion is possible only when all the errors are removed.

5.      Compiler automatically detects and indicates certain types of errors in source code.

6.      Once source code is translated to object code, object code is stored on secondary storage. There is no need to repeat compilation process unless there is modification in object code.

Interpreter

Interpreter is a program that translates high level language into machine level language.

It takes one statement of H.L.L and translates it into a machine instruction which is immediately executed. So in case of interpreter no object code is saved.

Features of Interpreter

1.      In case of interpreter the input to an interpreter is source code but unlike compiler its output is the result of program execution instead of an object code.

2.      No object code is saved so statement must be reinterpreted every time it is encountered during program execution.

3.      Interpreter is easy to design.

4.      It requires less memory space for execution

5.      Errors are detected during every statement execution so it easier and faster to correct programs.

6.      Interpreter is slower than compiler.