Examples of function declarations, definitions, and use

[sourcecode language=’cpp’]
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#include
/* Examples of declarations of functions */

void square1(void); /* Example of a function without input parameters
and without return value */

void square2(int i); /* Example of a function with one input parameter
and without return value */

int square3(void); /* Example of a function without input parameters
and with integer return value */

int square4(int i); /* Example of a function with one input parameter
and with integer return value */

int area(int b, int h); /* Example of a function with two input parameters
and with integer return value */

/* Main program: Using the various functions */
int main (void) {
square1(); /* Calling the square1 function */
square2(7); /* Calling the square2 function using 7 as actual
parameter corresponding to the formal parameter i */
printf(“The value of square3() is %d\n”, square3()); /* Ysing the square3
function */
printf(“The value of square4(5) is %d\n”, square4(5)); /* Using the square4
function with 5 as actual parameter corresponding to i */
printf(“The value of area(3,7) is %d\n”, area(3,7)); /* Using the area
function with 3, 7 as actual parameters corresponding
to b, h respectively */
}

/* Definitions of the functions */

/* Function that reads from standard input an integer and prints
it out together with its sum */
void square1(void){
int x;

printf(“Please enter an integer > “);
scanf(“%d”, &x);
printf(“The square of %d is %d\n”, x, x*x);
}

/* Function that prints i together with its sum */
void square2(int i){
printf(“The square of %d is %d\n”, i, i*i);
}

/* Function that reads from standard input an integer and returns
its square */
int square3(void){
int x;
printf(“Please enter an integer > “);
scanf(“%d”, &x);
return (x*x);
}

/* Function that returns the square of i */
int square4(int i){
return (i*i);
}

/* Function that returns the area of the rectangle with base b
and hight h */
int area(int b, int h){
return (b*h);
}

/* The output of this program is:

Please enter an integer > 3
The square of 3 is 9
The square of 7 is 49
Please enter an integer > 4
The value of square3() is 16
The value of square4(5) is 25
The value of area(3,7) is 21

*/[/sourcecode]