Developing Software Solutions

 

 

 

 

 

 

 

 

 

 

 

Conditional Statements

There are many wasys of asking a question in a program. The reason for asking a question could be to save doing unnecessary calculations or to check that the user is no entering DUMB data.

 

 

 

 

Example 3.1

            This uses an IF...THEN...ELSE statement. If you enter a number between 4.5 and 5.5 the output is "ACCEPTABLE" otherwise it is "UNACCEPTABLE"

 

PROGRAM TestNumber;

 

VAR

            Number:real;

 

BEGIN

            Clrscr;

            Write('Enter the number: N= ');

            Read (Number);

            Writeln;

            Writeln;

            IF Number >=4.5 THEN

                        IF Number <=5.5 THEN

                                    Writeln('ACCEPTABLE')

                        ELSE

                                    Writeln('UNACCEPTABLE')

            ELSE

                        Writeln('UNACCEPTABLE')

END.

 

    

 

 

Example 3.2

            This uses a CASE...ELSE which is useful if there are more than two answers to a question. Note that there are two END statements.

 

PROGRAM Colour:

 

VAR

            Entry:integer;

 

BEGIN

            Clrscr;

            Writeln('Enter a number 1,2,3 or 4 and a colour name is displayed');

            Read(Entry);

            CASE Entry OF

                        1: Writeln('Brown');

                        2: Writeln ('Red');

                        3: Writeln('Orange');

                        4:Writeln('Yellow');

            ELSE

                        Writeln('This is an invalid entry');

            END

END.

 

    

Looping Operations

A looping operation is a way to get the computer to do the same job over and over again.

 

Example 3.3

This is a WHILE/DO LOOP. note how TESTSCORE and COUNT are set to zero at the beginning. The WRITE statement in the loop to tell you what the COUNT is each time.

 

PROGRAM Test_Average;

 

VAR

            Number, Count: integer;

            TestScore, Sum, Average:real;

 

BEGIN

            Clrscr;

            Writeln('This program will work out the average of any number');

            Writeln('of test scores');

            Writeln;

            Writeln;

            Write('Enter the number of scores you wish to average: Number= ');

            Readln(Number);

            Writeln;

            Writeln;

            TestScore:=0;

            Count:=0;

            WHILE Count < Number DO

                        BEGIN

                                    Count:=Count+1;

                                    Write('Enter test score #',Count,': ');

                                    Readln(TestScore);

                                    Sum:=Sum+TestScore

                        END; {while}

            Average:=Sum/Number;

            Writeln;

            Writeln;

            Writeln('The average of ',Number,'scores is ',Average:5:2)

END.

 

 

Exercise 3.4

Write a Pascal program. It should be handwritten on A4 paper.

You can use a WHILE/DO LOOP to work out reciprocal equation.

S:=S+1/R

This refers to Tasks 1.3,1.4, 1.5

 

This is due 28^th February

 

    
Example 3.5

            This is a REPEAT/UNTIL LOOP. Note how COUNT is set to 0.  This program works out the sum of numbers entered.

 

PROGRAM SUM;

 

VAR

            Number, Count:integer;

            RT,R1,R:real;

 

BEGIN

            Clrscr;

            Writeln('This program will work out the sum of numbers entered');

            Writeln;

            Writeln;

            Write('Enter the number of numbers to be added: Number = ';

            Readln(Number);

            Writeln;

            Count:=0;

            REPEAT         

                        Count:=Count+1;

                        Write('Enter number #',Count,' = ');

                        Read(R);

                        IF Count=1 THEN

                                    RT:=R

                        ELSE

                                    RT:=RT+R

            UNTIL Count = Number;

            Write ('The total sum is RT);

END.

 

 

    
Example 3.6

            This is a FOR/DO LOOP. Note how TestScore is set to zero.

 

PROGRAM Test_Average;

 

VAR

            Number, Count:integer;

            TestScore,Sum,Average:real;

 

BEGIN

            Clrscr;

            Writeln('This program will work out the average of test scores');

            Writeln;

            Writeln;

            Write('Enter the number of scores you wish to average: Number = ');

            Readln(Number);

            Writeln;

            Writeln;

            TestScore:=0;

            FOR Count:=1 TO Number DO

                        BEGIN

                                    Write('Enter test score #',Count,': ';

                                    Readln(TestScore);

                                    Sum:=Sum+TestScore

                        END; {for loop}

            Average:=Sum/Number;

            Writeln;

            Writeln;

            Writeln('The average of ',Number,' scores is ',Average:5:2)

END.