Chapter 1 Reasons to study concepts of PLs. 1. To Increase ability - - PDF document

CSCI325 Concept of Programming Languages, Dr Ahmed Rafea 1

Chapter 1

Reasons to study concepts

• f PLs.
• 1. To Increase ability to learn new

languages

• 2. To Increase ability to design

new languages

• 3. To choose appropriate

languages

CSCI325 Concept of Programming Languages, Dr Ahmed Rafea 2

Chapter 1

What is a Programming Language? A Programming Language is a notational system for describing computation in machine-readable and human-readable form Computation- Processing Any process that can be carried out by a computer Machine-Readability For a language to be readable, it must have a simple enough structure to allow for efficient translation Human-Readability Unlike machine-readability, this is a much less precise notion, and it is also less understood. It requires that a programming language provide abstractions of the actions

• f computer that are easy to understand by persons not

completely familiar with the underlying details of the machine.

CSCI325 Concept of Programming Languages, Dr Ahmed Rafea 3

Chapter 1

Abstractions in Programming Languages

• Data abstractions
• Basic abstractions
• E.g. variables and types
• Structured abstraction
• E.g. arrays and records
• Unit abstraction
• E.g. ADT, packages, class, module
• Control abstractions
• Basic abstractions
• E.g. assignment statement
• Structured abstraction
• E.g. if-statement, procedure declaration and

invocation

• Unit abstraction
• E.g. a collection of procedures, unit, the

same as unit-level data abstraction

• Parallel Programming
• E.g. threads, tasks

CSCI325 Concept of Programming Languages, Dr Ahmed Rafea 4

Chapter 1

Computational Paradigms

• 1. Imperative ( procedural)

A programming language that is characterized by the sequential execution of instructions , the use of variables representing memory locations and the use of assignment to change the values

• f varables is called imperative langauge, the

Von Neumann model

• 2. Functional (applicative)

The functional paradigm bases the description of computation on the evaluation of functions or tha application of functions to known values

• 3. Logic

This language paradigm is based on symbolic logic

• 4. Object-oriented (closely related to imperative)

The OOP is based on the notion of object which can be loosely described as a collection of memory locations together with all the operations that can change the values of these memory locations.

CSCI325 Concept of Programming Languages, Dr Ahmed Rafea 5

Chapter 1

Language Implementation

• 1. Compilation
• Translate high-level program to machine code
• Slow translation
• Fast execution
• 2. Pure interpretation
• No translation
• Slow execution
• Becoming rare
• 3. Hybrid implementation systems
• Small translation cost
• Medium execution speed