Lecture 02

Question 1

Algol

Answer 1

Algol (ALGOrithmic Language),
designed to overcome
the problems of FORTRAN in the late 50s

Question 2

Algol 60 Major Concepts

Answer 2

• use of formal notation for syntax (BNF notation - lecture 5);

– block structure (with locally-defined variables);

– recursive procedures; and

– “readable” if and for statements.

Question 3

Pascal

Answer 3

It is a direct descendant of Algol, intended to be more
efficient in order to compete with Fortran as a general purpose language.

Pascal compiler was designed to be portable, by compiling to a virtual machine (the p-code
system).

Pascal became popular in the late 70s as a teaching
language in universities

More recent versions of Pascal have added modules and classes (e.g., the Object Pascal language, also called
Delphi)

Question 4

Pascal continued

Answer 4

The program statement is a required first line of every program.

Program must have a name.

• input means that the keyboard may be used to put information into the program.

– output means that the program may write information to the video display.

program must have a “begin” to mark, likewise with an “end” statement too.

Question 5

C

Answer 5

Fortran and COBOL proved successful in the 60s.

C was developed in 1972, alongside UNIX OS at Bell Labs.

C has high-level features like functions, loops and has low-level operations like arithmetic on memory addresses.

Question 6

Object Oriented Language

Answer 6

Major application of computers is simulation of real-world systems.

Early programming languages developed for simulation include GPSS (1961) and Simula 1 (1965).

Designers of Simula, Dahl, Nygaard added the concept of the “class” to represent simulated entitites.

Simula 67 is considered as orginial object oreintated language.

Influential object-orientated languages that followed Simula 67 include Smalltalk (1980) and Eiffel (1986).

Question 7

Scripting Languages

Answer 7

They are used to write programs that run for a special run-time environment that automate execution of tasks, or alternatively be executed by one-by-one by a human operator. For example shell scripts (CLI).

Question 8

Scripting Languages Examples

Answer 8

High Level languages such as Perl, Python, Ruby, PHP, JavaScript, and MatLab.

Scripting languages have a simple syntax and semantics, interpreted and intended to be very fast to learn and write in.

Question 9

Logical Languages: Prolog

Answer 9

ProLog building blocks are variables, constants, and structures.

Variables begin with capital letter.

Constants are either atoms like words or integers.

Structures consist of functor and arguments.

Question 10

Prolog Queries

Answer 10

Used to answer queries ( arithmetic operations possible)

Query is a fact or rule that initiates a search for success in Prolog program.

Question 11

Language Evaluation Criteria

Answer 11

Simplicity
Lexical elements.
Orthogonality
Control Structures
Data Types
Expressiveness
Type Checking
Exception Handling.

Question 12

Simplicity

Answer 12

Language with simple syntax and small number of constructs. Smalltalk is considered simple vs C++ which is complex/large.

Programmers tend to learn only a subset of large language.

An example is i++, i = i + 1 in C++ and Java.