This document will help you to understand the main features as well as contribution of ADA ALGOL PASCAL languages, major strengths and weakness of them clearly.

1. Sri Lanka Institute of Information Technology
Programming Language Design Concepts
Unit Code: IT340
Year 3, Semester 1 – 2015
Topic: Evaluate and analyze Algol, Pascal and ADA programming
languages
Student Information:
No
Student Registration
Number
Student Name
1 IT13118082 Charitha D.G.

2. Major contribution of ALGOL
1. The assignment operation
2. The block structure
3. Regularity of language
4. Guided the notation to define the syntax of programming languages
5. Dynamic memory management
6. Introduction of the programming language concept
Major contribution of Pascal
1. Pascal contributed some features such as simplicity, security and reliability
2. Type safety: Pascal was seminal in creating the belief that type safety is important and critical in
a language.
3. Compiler efficiency
Major contribution of ADA
1. Portability
2. Reuse of software
3. Support to large scale software systems
Main Features of ALGOL
The statements are of two types: declarative statements and imperative statements. The declarative
statements were used for variable declarations, procedure declarations and switch declarations. In Algol
variable names did not have restrictions on the number of characters used. Mainly three data types
used as integer, real and string. Arrays in Algol are generalizes and dynamic: space is allocated at block
entry time and fixed until block exit. Alogol-60 had strong typing and keywords. There are control
structures in Algol as goto, if-then-else, for loop, switch conditions. There are two ways of parameter
passing as call by value (copy going into the procedure), call by reference (pass a pointer to the actual
parameter. And indirect through the pointer), call by result (copy going out of the procedure), call by
value result (copy going in, and again going out)
Strengths:
 Strong typing
 Efficiency
 Easy to read and learn
 Allows procedures to be recursive
Weaknesses
 Lack of input-output statements was a mistake
 Dynamic scoping in Algol makes programs a lot more difficult to read
 Display method in Algol requires extra memory for the array implementing the display

3. Main features of Pascal
A Pascal program is formed from a single main program block which contains within it the definitions of
the subprograms used. A Pascal program basically consists of heading statement, a declaration and an
execution part strictly in that order. In Pascal variable declarations are introduced by using the keyword
var – syntax is name: type. The type declarations are introduced by the keyword type –syntax is name =
type. The type declaration is used to declare the data type of an identifier. Syntax of type declaration is:
type-identifier-1, type-identfier-2 = type-specifier; Pascal adds character (char) and a secure (typed)
pointer type to Algol's real, integer, and Boolean types. Pascal has more control constructs than Algol-
60, but they are simpler and more structured. Pascal's for loop is restricted to definite iteration -- it
steps only by increments of 1, upward or downward. Pascal provides two constructs for indefinite
iteration: a leading-decision iterator and a trailing-decision iterator. Pascal introduced labeled case-
statement Pascal supports only pass by value and pass by reference.
Strengths:
 Strong data typing
 Simplicity and expressivity
 Supports structured programming
 Ability to write your own libraries
 Easy compilation to .EXE programs
 Security and reliability
Weaknesses
 Not mainstream
 Weak String Handling Capabilities
 Pascal Does Not Support Object Oriented Programming
 Pascal is Not For Serious Programmers

4. Main features of ADA
Packages are the principle structuring facility in Ada. Packages are intended to be used to directly
support abstraction, information hiding, and modularization. For example, packages are useful for
encapsulating machine dependencies. Variable declarations in ADA allow the initialization of the
variable. ADA uses fully bracketed syntax. Ada control structures are designed for maximum readability,
all control structures are clearly ended with an 'end something'. The case statement must have an action
for every possible value of the case item. The compiler checks that this is the case. All Ada looping
constructs use the loop/ end loop form. Several variations exist. The exit statement can be used to break
out of loops. The goto statement is provided in Ada for use in exceptional situations. ADA has three
parameter passing modes called IN, OUT, IN OUT. IN is the same as call by value, OUT is the same as call
by result, and IN OUT is the same as call by value result. In addition, IN parameters are local constants --
you can't assign into them.
Strengths:
 Safe type system
 Modularity
 Information hiding
 Readability
 Portability
 Standardization
 Interoperability with other languages
 Successful usage in practice
Weaknesses
 Complexity of language
 Compiler inefficiency (Ada 83)
 Implementation is expensive
 Increased cost of validation due to complexity of language