Third generation software languages

Late 1950's - High Level Languages
Sample
/* HELLO.C -- Hello, world in C*/ #include <stdio.h> main() { printf("Hello, world\n"); }

Examples

BASIC (Beginners All-purpose Symbolic Instruction Code)

COBOL (Common Business Oriented Language)

C, C++

Pascal, and

Many, many more !!

Characteristics

Late 1950's

High Level Languages
FORTRAN, COBOL, PL/1, BASIC
Application Packages
Database Languages
English-type words/statements
Less dependency on environment
Friendlier interface

Translated by;

Compiler (to OBJect file) then LINKED or;
Interpreter
Generally Procedural in nature
Packaged, re-useable solutions

Users

Programmer
Data Processing Professional

Compiled Code

Code is typed into a text file

This code is then "Compiled" and "Linked" to produce a "Machine code" program.

This machine code program is then executed by the computer.

May be likened to a speech being typed out, then given to a translator to convert to another language. The text of the converted speech is then distributed.

Mush faster than interpreted code.

Interpreted Code

A program is used to enter the "code".

Each line of code is then "interpreted" before execution by the computer.

May be likened to a speech being delivered with the aid of an interpreter. As each sentence is completed the interpreter converts it and relays it to the audience.

Much slower than compiled code.

Commonly used in "BASIC", though with the advent of faster computers, a program is now usually compiled.

Procedural structure

HOW the task needs to be accomplished

Programming Languages

Programmers must say what the desired results are and how they will be achieved

Through the definition of a set of executable instructions that are executed in a predefined sequence
ie. Concerned with computer procedures

Samples

Hello World in Pascal, Basic and COBOL

Pascal

{ HELLO.PAS -- Hello, world } program HelloWorld; begin writeln('Hello, world'); end.

BASIC

BASIC (Beginners All-purpose Symbolic Code)

REM HELLO.BAS - Hello World PRINT "Hello, World" END

The following instructions are entered into the BASIC development software

INPUT "Enter Your Name, and Press [Enter] ", A$ PRINT "Hello "+A$

When interpreted by the computer ( You type in the bit in red, [Enter] is the [Enter] key )

Enter Your Name, and Press [Enter] ? Michael[Enter] Hello Michael

C

/* HELLO.C -- Hello, world in C*/ #include <stdio.h> main() { printf("Hello, world\n"); }

The world's last C bug

while (1) { status = GetRadarInfo(); if status = 1) LaunchMissiles(); }

(Keall 1995, Nov)

COBOL

COBOL (Common Business Oriented Language)

IDENTIFICATION DIVISION. ENVIRONMENT DIVISION. DATA DIVISION. PROCEDURE DIVISION. A0000-PRINT-PARAGRAPH. DISPLAY "Hello, World". STOP RUN.

Selecting a language

Selecting a Programming Language Made Easy

==========================================

Daniel Solomon & David Rosenblueth
Department of Computer Science, University of Waterloo
Waterloo, Ontario, Canada N2L 3G1

With such a large selection of programming languages, it can be difficult to choose one for a particular project. Reading the manuals to evaluate the languages is a time-consuming process. On the other hand, most people already have a fairly good idea of how various automobiles compare. So in order to assist those trying to choose a language, we have prepared a chart that matches programming languages with comparable automobiles:

Assembler A Formula I race car. Very fast, but difficult to drive and expensive to maintain.

FORTRAN II A Model T Ford. Once it was king of the road.

FORTRAN IV A Model A Ford.

FORTRAN 77 A six-cylinder Ford Fairlane with standard transmission and no seat belts.

COBOL A delivery van. It's bulky and ugly, but it does the work.

BASIC A second-hand Rambler with a rebuilt engine and patched upholstery. Your dad bought it for you to learn to drive. You'll ditch the car as soon as you can afford a new one.

PL/I A Cadillac convertible with automatic transmission, a two-tone paint job, white-wall tires, chrome exhaust pipes, and fuzzy dice hanging in the windshield

C A black Firebird, the all-macho car. Comes with optional seat belts (lint) and optional fuzz buster (escape to assembler).

ALGOL 60 An Austin Mini. Boy, that's a small car.

Pascal A Volkswagon Beetle. It's small but sturdy. Was once popular with intellectuals.

Modula II A Volkswagon Rabbit with a trailer hitch.

ALGOL 68 An Astin Martin. An impressive car, but not just anyone can drive it.

LISP An electric car. It's simple but slow. Seat belts are not available.

PROLOG/LUCID Prototype concept-cars.

Maple/MACSYMA All-terrain vehicles.

FORTH A go-cart.

LOGO A kiddie's replica of a Rolls Royce. Comes with a real engine and a working horn.

APL A double-decker bus. Its takes rows and columns of passengers to the same place all at the same time. But, it drives only in reverse gear, and is instrumented in Greek.

Ada An army-green Mercedes-Benz staff car. Power steering, power brakes and automatic transmission are all standard. No other colors or options are available. If it's good enough for the generals, it's good enough for you. Manufacturing delays due to difficulties reading the design specification are starting to clear up.