write a program that uses a function to swap values stored in two integer variables to understand the concept of global variables.

C Programming Language Function in C Language (Article) Function in C Language (Program)

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Program:

#include<stdio.h>

void exchange(void);
int a, b; /* declaration of global variables */

int main()
{ /* main program starts here...*/
	a = 5;
	b = 7;
	printf(" In main: a = %d, b = %d\n", a, b);
	exchange(); /* function call, no parameters are passed */
	printf("\n Back in main: ");
	printf("a = %d, b = %d\n", a, b);
	return 0;
} /* main program ends here */

void exchange(void)
{ /* function body starts here...*/
	int temp; /* decl. of local variable in function*/
	printf("\n In function exchange() before change: just received from\
	main... a=%d and b=%d",a,b);
	temp = a;
	a = b;
	b = temp; /* interchange over */
	printf("\n In function exchange() after change: ");
	printf("a = %d, b = %d\n", a, b);
} /* function body ends here*/
 

Output:

 In main: a = 5, b = 7

 In function exchange() before change: just received from       main... a=5 and
b=7
 In function exchange() after change: a = 7, b = 5

 Back in main: a = 7, b = 5

Explanation:

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