Programming for A2 Computing High Level Languages By David Halliday Module 4

High and Low Level languages High Level languages Examples: C, C++ Pascal BASIC Portable (can be compiled on different systems) Problem oriented (designed around solving different types of problem) Statements resemble English language (formalised) Low level Languages Examples Assembly Machine Oriented: designed for individual machine or processor architectures Each statement translates into one machine instruction Statements resemble machine instructions in mnemonics

High Level languages

Examples:

C, C++

Pascal

BASIC

Portable (can be compiled on different systems)

Problem oriented (designed around solving different types of problem)

Statements resemble English language (formalised)

Low level Languages

Examples

Assembly

Machine Oriented: designed for individual machine or processor architectures

Each statement translates into one machine instruction

Statements resemble machine instructions in mnemonics

High Level Language Facilities Selection statements: If, Then, Else, Case Iteration (repetition) statements: While...EndWhile, Repeat...Until, For… EndFor Built in/Library routines, functions and enumerated data types to simplify I/O Readln, writeln Sqr, log String, Array, Record

Selection statements:

If, Then, Else, Case

Iteration (repetition) statements:

While...EndWhile, Repeat...Until, For… EndFor

Built in/Library routines, functions and enumerated data types to simplify I/O

Readln, writeln

Sqr, log

String, Array, Record

High Level Language Paradigms High level languages often fit into one of 3 categories Imperative (procedural) Imperative programs explicitly specify an algorithm to achieve a goal Examples include: C, C++ Pascal Fortran Declarative Declarative programs explicitly specify the goal and leave the implementation of the algorithm to the support software Examples include: Prolog Functional Emphasizes the application of functions, unlike imperative programming, which emphasizes changes in state and the execution of sequential commands. Examples include: Haskell

High level languages often fit into one of 3 categories

Imperative (procedural)

Imperative programs explicitly specify an algorithm to achieve a goal

Examples include:

C, C++

Pascal

Fortran

Declarative

Declarative programs explicitly specify the goal and leave the implementation of the algorithm to the support software

Examples include:

Prolog

Functional

Emphasizes the application of functions, unlike imperative programming, which emphasizes changes in state and the execution of sequential commands.

Examples include:

Haskell

Imperative (procedural) Languages Imperative programs explicitly specify an algorithm to achieve a goal They are concerned with changing of states of variables in memory The closest paradigm to assembly/machine code Problem Oriented… They are developed to solve particular types of problem: FORTRAN (FORmula TRANslation) dev'd in 1950s for use in scientific and engineering COBOL (COmmon Business Oriented Language) dev'd in 1950s for data processing (first to use records) 'C‘ developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. Pascal dev'd in 1970s to teach structured programming Extended by Boreland with Delphi making a useful RAD tool

Imperative programs explicitly specify an algorithm to achieve a goal

They are concerned with changing of states of variables in memory

The closest paradigm to assembly/machine code

Problem Oriented… They are developed to solve particular types of problem:

FORTRAN (FORmula TRANslation)

dev'd in 1950s for use in scientific and engineering

COBOL (COmmon Business Oriented Language)

dev'd in 1950s for data processing (first to use records)

'C‘

developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system.

Pascal

dev'd in 1970s to teach structured programming

Extended by Boreland with Delphi making a useful RAD tool

Embedded systems Computer is component in a larger system. Examples include: microprocessor-controlled washing machine or video recorder; a modern jet aircraft; a system for controlling traffic lights; a process control system for controlling the flow of water along a pipe by means of a valve; a robot used in a car assembly plant. Modern mobile phones

Computer is component in a larger system.

Examples include:

microprocessor-controlled washing machine or video recorder;

a modern jet aircraft;

a system for controlling traffic lights;

a process control system for controlling the flow of water along a pipe by means of a valve;

a robot used in a car assembly plant.

Modern mobile phones

Criteria for Selecting a Language The nature of the application; The availability of facilities within the language for implementing the software design; The availability of a suitable compiler/interpreter for the hardware; The expertise of the programmers.

The nature of the application;

The availability of facilities within the language for implementing the software design;

The availability of a suitable compiler/interpreter for the hardware;

The expertise of the programmers.

Homework Heathcote Chapter 35 Page 219 All Questions

Heathcote Chapter 35 Page 219 All Questions