CP1020 University of Wolverhampton - Steve Garner and Ian Coulson1 Week 1 - Principles of...

CP1020 University of Wolverhampton - Steve Garner and Ian Coulson

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Week 1 - Principles of programming

Welcome from the Presenters Steve Garner

and Dr Ian Coulson


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Essential information [1]

The module is a means to learn programming principles

Quick Basic is a language to do this -available on most machines which have DOS, Windows or NT

We assume you know NOTHING about programming a computer


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Essential Information [2]

Module continually assessed

1 workshop exercises weeks 2 to 11 - 40%

2 Assignment 1 week 5 - 35%Assignment 2 week 12 - 25%

You must PASS BOTH of these components

1 hour lecture, 3 hour workshop


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Essential information [3]

You must attend ALL lectures, workshops and work in study time

To learn this subject you must actually do the practical work, (like riding a bike)!

You must have the course book - QBasic 2nd ed. - Bauman and Mandell 0314206590


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Principles of computingComputer hardware consists of several

fundamental parts - monitor, system and keyboard

A Computer programme is set of instructions that tells the computer what to do. Written in English and interpreted into the computers working language (Binary), and then executed.

It is too difficult for humans to work in computer language directly !


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How to tackle a problem

We will now look at how we will tackle a real problem

we will go through the steps needed to produce a working program


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Where to startWhy programme ?

All computers require a program in order to work. i.e. Word processing package has been written using a programming language.

First… look at the thing we are trying to get the computer to do.i.e. add two numbers

To produce the program we must follow a series of steps


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The Steps (it’s all down hill)

Program

Problem

Analysis & Design

Testing

Document

Review Solution

Start


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Problem - Requirements and Specification

Develop a full understanding of the problemCan be difficult to do:

Users do not know what they want!Users keep changing their minds!

Once the problem is understood, a Program Specification can be produced

This specification will summarise the problem, and act as the agreement of what the developers must produce for the users


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Analysis & Design [1]

Once we fully understand the problem, then we can attempt to design a solution.

Probably the most important stage of the process as a good design will greatly simplify later steps

Will involve looking at: Input data and corresponding output data What processing is involved


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Analysis & Design [2]

There are many design techniques used, we will use what is known as pseudo code simply write down the steps in words -

known as pseudo code


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Testing

We must test the design to ensure it gives the correct answers.

By using sample data and applying the pseudo code steps to it, we can prove the design works.


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Program or Coding

The design and testing must be complete before this stage

You should know what you want to achieve before beginning to code it!

It should now be quite straightforward to implement our designs in code


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Document

If anyone else needs to look at or run your program it will need DOCUMENTING

What the problem isHow did you design it?How did you test it?What sort of data does it use?What does each line of code do?How do you run it?


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An example problem

We wish to design and code a program that will convert a measurement in kilometres to it’s equivalent in miles - write down the steps needed in the program

We will set the constraint that input of the number of Kilometres will be from the keyboard, and the result displayed in miles on the screen


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Analysis and Design

a. Read the Problemb. Read it again!c. Do it on paper

test datatest algorithmscheck results

d. Produce Design


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a. Read The Problem

a. Read the Specification - Understandable - OK

b. Read it again Identify the purpose of program :-

To calculate the number of kilometres equivalent to a given number of miles


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c. Do it on Paper

c. Do it on paper A typical number of kilometres inputted

may be 3. the answer should be 1.86 miles

as 1 mile is equal to 1.61 km


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Output to be displayed (with suitable instructions ):

Enter the number of miles : 3 Users input

There are 1.86 miles in 3 kilometres

Screen output


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Prepare Design [1]

The first simple design, in pseudo code, would be: 1. enter number of km. 2. Calculate miles. 3. Display the answer.

These steps can be broken down further


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Prepare Design [2]

New, more detailed, design:1. Get number of km

1.1 Prompt user to enter the number of km 1.2 Read in the km from the keyboard

2. Calculate miles 2.1 divide km by number of km in one mile

3. Display the number of miles 3.1 Display number of miles with corresponding

message


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The solution - Prepare code

REM program : to convert miles to kilometresREM written by : Ian CoulsonREM date written: 15/9/98

DIM Km AS SINGLE ‘Create variablesDIM Miles AS SINGLE

CLS ‘this will clear the screenPRINT “This program converts km to miles.” ‘ message

INPUT “Enter the number of km to be converted; “, km

LET Miles = km / 1.61 ‘calculation

PRINT “There are”; Miles; “miles in”; km; “kilometres.” END


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Using Print statements

Your first steps in learning to programme is usually to display a suitable message on the screen

The keyword PRINT in Qbasic is an instruction to display something on the screen.

Here is the way it works


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Using the print statement

The Print statement has the format

PRINT “This is the text I want displayed on the screen”

Use the Print keyword

Enclose the text to bedisplayed in quotation marks

This is the text I want displayed on the screen

Resultingoutput on the screen


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Printing on the screenQbasic divides the screen into 80 columns

and 25 rows.

25 rows

80 columnsQbasic has a number of mechanisms to arrange where on the screen you wish to print informationHave a look at the following examples


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Print formatting

PRINT “This is the first thing printed ”PRINT “Next thing printed”

This is the first thing printedNext thing printed

Each print statement causes a new row to be used


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Print formatting - using the ; character

PRINT “This is the first thing printed ”;PRINT “Next thing printed”

This is the first thing printedNext thing printed

The ; causes the next string to be printed starting in the next column on the same line


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Print formatting using the , character

PRINT “This is the first thing printed ”,PRINT “Next thing printed”

The , causes the next string to be printed in the next available print zone

This is the first thing printed Next thing printed

The screen is divided into 5 print zones each 14columns wide

14 columns


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Questions

1 Why don’t we program in the computers natural language directly ?

2 Why do we need to go through all the Steps to write a program ?

3 Write the code to display the message Hello World on the screen

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http://www.wlv.ac.uk/~cm1810/CP1020/

CP1020 University of Wolverhampton - Steve Garner and Ian Coulson1 Week 1 - Principles of...

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