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Symbolic constant in c Language
A symbolic constant is name that substitute for a
sequence of character that cannot be changed. The character may represent a
numeric constant, a character constant, or a string. When the program is
compiled, each occurrence of a symbolic constant is replaced by its
corresponding character sequence. They are usually defined at the
beginning of the program. The symbolic constants may then appear later in the
program in place of the numeric constants, character constants, etc., that the
symbolic constants represent.
For example, a C program consists of the following symbolic constant
definitions.
#define PI 3.141593
#define TRUE 1
#define FALSE 0
#define PI 3.141593 defines a symbolic constant PI whose
value is
3.141593. When the program is preprocessed, all occurrences of the
symbolic constant PI are replaced with the replacement text 3.141593.
Note that the preprocessor statements begin with a #symbol, and are
not end with a semicolon. By convention, preprocessor constants are written in
UPPERCASE.
Example: 1
#include<stdio.h>
#include<conio.h>
#define TRUE 1
#define PI 3.141593
void main()
{
float a;
float b;
float c;
float d=PI;
clrscr();
if(TRUE)
{
a=100;
b=a*10;
c=b-a;
}
printf("\na=%f\nb=%f\nc=%f\nPI=%f",a,b,c,d);
getch();
}
Example: 2
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