STRUCTURE OF A PASCAL PROGRAM / PDF
STRUCTURE OF A PASCAL PROGRAM / PDF
Sample of the PDF document
Program Heading
This is the
opening statement of all Pascal programs. In this section the program is given
a name which should not contain any space or special character. Standard I/O devices are referred to as
(Input, Output).
Format
Program program-name
(Input, Output);
Example
Program
SUM (Input, Output);
Constant Declaration
Any constant
value to be used in the program may be declared (assigned) here, and the name
of the constant used in the program instead of the actual value. This allows for easy modification of the
program in case we need to change the value of the constant. This concept is similar to the use of Absolute
Addressing in spreadsheets.
Format
const constant-name = value-of-constant;
Example
const int-rate = 0.15;
Variable Declaration
Each variable
that is used in the program must be declared in this section, along with its
data type. The most common data types we
will encounter at this level are Integer, Real and String.
Format
var variable-name : data-type;
variable-name : data-type;
Example
var A, B : Integer;
C : Real;
Name : String[20];
Body of Program
This section
contains all the executable statements of the program, and is generated from
the pseudocode algorithm we would have written prior to attempting to write the
program.
Structure
1.
This section must start with
the reserved word begin and terminate with the reserved word end, followed by a full-stop.
2.
Each statement is terminated by
a semi-colon (;).
3.
:= is used to represent the assignment symbol.
4.
The format of the input
statement is:
Read (variable-name);
5.
The format of the output
statement is:
Either
Write
(variable-name);
Or
Write
(‘comments’);
6.
When using a conditional
statement, (i.e. IF-THEN, FOR-DO, WHILE-DO, DO-UNTIL), we should note the
following:
(a)
Each conditional statement is considered to be a single
statement, and is terminated
with a semi-colon.
Example
If A > B then
A:= A – 10
else
B := B – 10;
(b)
If more than one statement is contained within a
statement-block, then they
should be enclosed within a begin-end pair.
Example
If A > B then
begin
A:=
A – 10;
Write (A);
end
else
begin
B := B – 10;
Write (B);
end;
7.
Comments used to explain the
program are enclosed using the following for each comment line.
(* comments
*)
Example
Program Subtractten (Input, Output);
(* This program was written by Peter Davis
of Vere Tech, *) (* and was designed to read two values,
and to subtract 10 *) (* from the larger one and add ten to the
smaller one. *)
etc........
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