Course : Simple Pascal Programming / PDF

Course : Simple Pascal Programming / PDF

Sample of the PDF document

A program is a list of instructions written in predefined language.  A program aims to teach the computer to solve a problem step by step following a user-designed algorithm.

A.        Structure of a Simple Pascal Program

PROGRAM FtoC(input,output);............................Program heading

USES WinCrt;                                                                Display results in windows

VAR

            fahr, celsius : Real;...............variable declaration

BEGIN

     Writeln('Temperature Converter');

     Writeln('Fahrenheit to Celsius');

     Write (‘Temperature in degree Fahrenheit? ’);

     Readln (fahr);                                

     celsius:=((fahr - 32)*5)/9;  

Writeln('Equals ', celsius:4:1,' degrees Celsius');

Writeln;

END.

1.         Program Heading

Program heading consists of the keyword PROGRAM, the name of the program, the program parameter.

2.         Variable Declarations

You should tell the computer the variables that you would use in your program. Then the computer will reserve space in RAM to store these variables. Variable declaration consists of the keyword VAR, the variables and their types. Multiple variables of the same type can be declared in the same statement.

Data type for variables: integer, real, char, string

3.         BEGIN and END

BEGIN and END signal respectively the beginning and the end of a statement block.

4.         Input and Output Statement

Writeln (‘XXXXX’) can output a statement on the VDU.

Readln(fahr) will read a data entered by the keyboard into the variable identifier.

5.         Assignment Operator (:=)

Once a variable is declared, you may assign it a value using the assignment operator (:=). The assigned value can be a constant, another variable, or an expression. A variable must be put in the left-hand side of an assignment operator.

a := 30;

Celsius :=((fahr - 32)*5)/9;

Arithmetic signs: +, -, *, /

 

6.      Output format

Writeln('Equals ', celsius :4 :1,'degrees Celsius');

           

	The number of decimal place for a real number vairable

 

7.         Punctuation

The semicolon ( ; ) is used to separate statements.

The full stop ( . ) is used to indicate the end of the program.

*          Try to find out the different in output format of using “writeln” and “write”.

Exercise 1

1.          Write a PASCAL program to calculate the area and circumstance of circle by inputting the radius of the circle.

Given:

1.          Variables names:  radius, pi, area, circumstance with data type : real

2.          pi := 3.1416

3.          Sample Output:

Please enter the radius? 8

The area of the circle is 201.1

The circumstance of the circle is 50.3

B.        Condition/Selection Statement

IF condition is true THEN do statement one ELSE do statement two;

I.         Logical Operators

                        =,>,<,>=,<=,<>

, AND, OR

           

            Example 1:

            USES

WinCrt;

VAR

num : Integer;

BEGIN

Write('Input a number : ');

Readln(num);

IF num > 0 THEN Writeln(num,' is positive.');

Writeln('Goodbye.')

END.

Example 2:

USES

WinCrt;

VAR

num : integer;

BEGIN

Write('Input a number : ');

Readln(num);

IF (num >= 1) AND (num <=10)

THEN Writeln(num,' is between 1 and 10 inclusively.');

Writeln('Goodbye.')

END.

Example 3:

            USES

WinCrt;

VAR

num : Integer;

BEGIN

Write('Input a number : ');

Readln(num);

IF num>0 THEN Writeln(num,' is positive.')

ELSE Writeln(num,' is non-positive. ')

END.

Course :Simple Pascal Programming / PDF