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PASCAL PROGRAMMING

 

PROCEDURE IN PASCAL

While coding, the need to reuse a part of the code might arise. It is not a good practice to copy this part again within the program. Instead, PASCAL has components, that is subprograms called procedures and functions for this purpose. These two components are make the program easier to write, debug and enhances readability.

A procedure is a block of code which only runs when it is called. You can pass data, known as parameters, into a procedure. Procedures are used to perform certain actions. Why use procedures? To reuse code: define the code once, and use it many times. Procedures are subprograms that can return a single value or a group of results. Procedures have a set of parameters, value or variable. Value parameters are those which are only passed to the procedure, because otherwise the procedure would not be able to do the task it is said to. Value parameters do not change after the execution of procedures. They are given in the parentheses which comes after the procedure declaration. Variable parameters are those which may affect the execution of the procedure and need to be updated according to this procedure. They are also given in the parentheses after the procedure declaration, however they have a 'var' keyword before them to indicate that they are variable parameters.

 

Syntax to declare a procedure in pascal:

procedure procedureName(arg(s) : datatype1, arg(s) : datatype2 …);

begin

//statements

end;

TIP: Start with the keyword procedure

Program exercises implementing PROCEDURE in Pascal programming

Lab1

//Pascal program to display your details using procedure

program displayDetailsLabEx;

var

name1, name2 : string;

procedure displayDetails( var yourName : string; fullname : string);

begin

yourName := fullname;  //just like we assign a value to result variable

end;

 

begin

//pass values directly

displayDetails(name1, 'dmactutor');

displayDetails(name2, 'www.whitepaceblog.blogspot.com');

 

writeln('Your name is:: ', name1);

writeln('Your blog site is:: ', name2);

end.

 

 

Lab2

//Pascal program to calculate area of rectangle using procedure

program areaRectangleUsingProcedure;

var

answer, len, wid :real;

procedure calculateAreaRec( var area : real; length : real; width : real);

begin

area := length * width;

end;

 

begin

//ask users for input

writeln('Insert Length in cm''s');

readln(len);

writeln('Insert Width in cm''s');

readln(wid);

calculateAreaRec(answer, len, wid);

writeln('The area of rectangle is:: ', answer:0:2);

end.

TIP: Here, the procedure has three parameters, a variable and two values. area is the variable parameter, length and width are the value parameters. In the procedure call, the value of answer is passed to area, although it does not have any significant initial value, and the value of len is passed to length, while wid is passed to width, that is the input from the user. In the procedure, area gets the value length * width. Then, after the procedure has finished execution, the new value of area is passed to answer. Now, answer stores the calculated value and can be output with precision 2.

TIP2: If you separate the parameters with commas and decide to use one datatype, it generate error, saying 'variable identifier expected'

 

Lab3

//Pascal program to calculate area of rectangle using procedure

program areaRectangleUsingProcedure;

var

a1, a2, a3 : real;

procedure calculateAreaRec( var area : real; length : real; width : real);

begin

area := length * width;

end;

 

begin

//pass values directly

calculateAreaRec(a1, 5, 3);

calculateAreaRec(a2, 2.5, 8.13);

calculateAreaRec(a3, 12.9, 10.5);

writeln('The first area of rectangle is:: ', a1:0:2);

writeln('The second area of rectangle is:: ', a2:0:2);

writeln('The third area of rectangle is:: ', a3:0:2);

end.

 

 

Lab4

program lab4;

var

   n1, n2, n3,  min: integer;

procedure findMin(p, q, r: integer; var ans: integer);

//Finds the minimum of the 3 values

 

begin

   if p < q then

      ans:= p

   else

      ans:= q;

  

   if r < ans then

      ans:= r;

end;

 

begin

   writeln(' Insert three numbers: ');

   readln(n1, n2, n3);

  

   //call the procedure

   findMin(n1, n2, n3, min);

  

   writeln(' Minimum: ', min);

end.

OUPTUT

Insert three numbers:

45 20 199

Minimum: 20

 

 

FUNCTION IN PASCAL

Functions are similar to procedures, except that they return one value with a specified type and all its parameters should be input parameters, that is value parameters. That is only one value should be able to be changed.

Syntax to declare a function in Pascal:

function functionName(arg(s) : datatype1, arg(s) : datatype2 …) : datatype;

begin

//statements

end;

TIP: Start with keyword function

 

Program exercises implementing FUNCTION in Pascal programming


Lab5

//Pascal program to display your details using function

program displayDetailsLabEx;

var

fname : string;

function displayDetails(fullname : string) : string;

begin

displayDetails := fullname;

end;

 

//main

begin

 

fname := displayDetails('dmactutor');

writeln('Your Youtube handle is:: ', fname);

end.

 

Lab6

//Pascal program to calculate area of rectangle using function

program areaofRectLabEx;

var

answer, len, wid : real;

function areaRect(length, width:real) : real;

begin

areaRect := length * width;

end;

 

//main

begin

writeln('Insert length in cm''s ');

readln(len);

writeln('Insert width in cm''s ');

readln(wid);

 

answer := areaRect(len,wid);

writeln('The area of Rectangle is:: ', answer:0:2);

end.

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