PASCAL

Introduction:

This is a 3^rd generation language which mainly used as an instructional language.

Contribution to the modern programming languages:

1.        Introduced a new primitive data type ‘Character’ denoted as char in the programming language.

2.       

Features:

Ø  Program structure:

o   Single main block structure where all the subprograms were defined under that same block as nested levels as same as in ALGOL.

o   Two types of subprograms,

§  Functions

§  Procedures

Ø  Variable declaration:

Syntax is as follows,

                        <name> : <type>

Ø  Data types:

Declaration syntax is as follows,

<name> = <type>

Ø  Data structures:

Ø  Control structures:

For loop – loop variable was only incremented or decremented by one at a single time of the loop body execution.

Repeat – until loops and While – do loops are used – execution of indefinite iterations was possible.

Case statements are used.

Ø  Parameter passing mechanisms:

§  Pass by value

§  Pass by reference     

Strengths and Weaknesses:

Strengths:

§  More advance compared to the 2^nd generation programming languages.

§  More focused on its efficiency and the simplicity.

§  Depth of the data structures can be extended up to any depth.

Weaknesses:

o   Difficult to understand the programs as the variables are declared far away from the place they are used.

o   Not possible to compile modules independently as the extensions are exist all over the program.