c macros

Macros

MACRO is a String Replacer.

We DEFINE a SYMBOL as a DEFINITION

Whenever the SYMBOL is encountered in the Program the DEFINITION

attached to the SYMBOL is REPLACED.

Difference between Function and macro

The Parameter Mechanism Performed by a MACRO is Illegal Operation.

The Parameter Mechanism Performed by a FUNCTION is a Logical One.

In case of MACRO there will not be any TRANSFER of CONTROL.

The Definition of MACRO is already Stored in a TABLE and will be REPLACED

whenever the MACRO is CALLED at Compile Time.

Whenever a FUNCTION is called the CONTROL will JUMP from the MAIN

FUNCTION to the DEFINITION of the CALLED FUNCTION.

Program

#include<stdio.h>

#define UPPER 20

void main()

{

int x;

for(x = 1; x <= UPPER; x++)

printf("\nThe Value is : %d", x);

}

Program

#include<stdio.h>

#define PI 3.1415

void main()

{

float r, area;

printf("\nEneter Value of Radius : "); scanf("%f", &r);

area = PI * r * r;

printf("\nArea of The Circle is : %0.2f", area);

}

Program

#include <stdio.h>

#define SQR(x) x * x

void main()

{

int result, a;

printf("\nEneter Any Value : ");

scanf("%d", &a);

result = SQR (a + 2);

printf("\nThe Result is : %d", result);

}

Recursion

The ability of a FUNCTION to CALL ITSELF UNTIL BASE CONDITION is

reached is called RECURSION.

Properties of Recursive Procedure:

BASE CONDITION.

RECURSIVE STATEMENT.

Base condition

The BASE CONDITION of a recursive procedure indicates when the recursive

calls are going to be TERMINATED.

Recursive statement:

The RECURSIVE STATEMENT is used to reduce Nth order problem to (n-1)th

order.

Illustrative Examples

Factorial Using Recursion

Program

#include<stdio.h>

void main()

{

int factorial(int);

int m;

printf("\nEnter Any Number : "); scanf("%d", &m);

printf("\nFactorial of %d is %d.", m, factorial(m));

}

int factorial(int n)

{

int x, y;

if(n == 0)

return 1;

else

x = n - 1; y = factorial(x); return(n * y);

}

Finding ‘A’ to the power of ‘B’ using Recursion

Program

#include<stdio.h>

void main()

{

int power(int, int);

int a, b;

printf("\nEnter Values of a and b : ");

scanf("%d%d", &a, &b);

printf("\n%d To The Power of %d is %d.", a, b, power(a, b));

}

int power(a, b)

{

if(b == 0)

return 1;

else

return (a * power(a, b - 1));

}