Macros in C

Macros :

•   Macro is a process where an identifier in a program is replaced by a predefined string or value.
•   #define is a preprocessor statement and is used to define macros.

Syntax:

 Form 1 : (simple macro)

    #define  identifier    predefined_string or value

Example :

#define  pf   printf

#define sf   scanf

C – MACRO EXAMPLE PROGRAM :

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

#include<stdio.h> #include<conio.h> #define pf printf #define sf scanf #define vm void main() #define cls clrscr #define gt getch #define val 100 void main() {   int n;   cls();   printf("Enter a number : ");   scanf("%d",&n);   printf("Given Number  = "%d",n);   p("\nval = %d",val);   getch(); }

Form 2 : (complex macro   or   macro with arguments)

Syntax:

#define     identifier(arg-1,arg-2,……….arg-n)       definition

Example :

#define   square(x)     x*x

C – COMPLEX MACRO EXAMPLE PROGRAM :

1 2 3 4 5 6 7 8 9 10 11 12 13

#include<stdio.h> #include<conio.h> #define square(x) x*x void main() {   int n,s;   clrscr();   printf("Enter a number : ");   scanf("%d",&n);   s=square(n);   printf("Square of given number = %d",s);   getch(); }

Difference between function and macro :

Function	Macro
Function is a self contained block of statements.	Macro is a preprocessor statement.
Function replaces its return value	Macro replaces its definition.
We can use only specified  data types in functions.	In Macros Data types are generic.
Execution speed of function is less.	Execution speed of Macro is more compared to function.

C – MACRO EXAMPLE PROGRAM :

1 2 3 4 5 6 7 8 9 10 11

#include<stdio.h> #include<conio.h> //#define square(x) x*x //#define square(x) (x*x) void main() {   int n;   n=100/square(5);   printf("n = %d",n);   getch(); }