C Passing Pointers to Functions
C language allows you to pass pointers to functions; you simply need to declare the function parameters as pointer types.
In the following example, we pass a pointer to an unsigned long to the function, and change this value within the function:
Example
#include <stdio.h>
#include <time.h>
void getSeconds(unsigned long *par);
int main ()
{
unsigned long sec;
getSeconds( &sec );
/* Output the actual value */
printf("Number of seconds: %ld\n", sec );
return 0;
}
void getSeconds(unsigned long *par)
{
/* Get the current number of seconds */
*par = time( NULL );
return;
}
#include <time.h>
void getSeconds(unsigned long *par);
int main ()
{
unsigned long sec;
getSeconds( &sec );
/* Output the actual value */
printf("Number of seconds: %ld\n", sec );
return 0;
}
void getSeconds(unsigned long *par)
{
/* Get the current number of seconds */
*par = time( NULL );
return;
}
( ) calling the write operation, and so on. In practice, the pointer action can be associated with a mouse or other GUI objects to achieve the corresponding purpose.
Number of seconds :1294450468
Functions that can accept pointers as parameters can also accept arrays as parameters, as shown below:
Example
#include <stdio.h>
/* Function declaration */
double getAverage(int *arr, int size);
int main ()
{
/* An integer array with 5 elements */
int balance[5] = {1000, 2, 3, 17, 50};
double avg;
/* Pass a pointer to the array as an argument */
avg = getAverage( balance, 5 ) ;
/* Output the return value */
printf("Average value is: %f\n", avg );
return 0;
}
double getAverage(int *arr, int size)
{
int i, sum = 0;
double avg;
for (i = 0; i < size; ++i)
{
sum += arr[i];
}
avg = (double)sum / size;
return avg;
}
/* Function declaration */
double getAverage(int *arr, int size);
int main ()
{
/* An integer array with 5 elements */
int balance[5] = {1000, 2, 3, 17, 50};
double avg;
/* Pass a pointer to the array as an argument */
avg = getAverage( balance, 5 ) ;
/* Output the return value */
printf("Average value is: %f\n", avg );
return 0;
}
double getAverage(int *arr, int size)
{
int i, sum = 0;
double avg;
for (i = 0; i < size; ++i)
{
sum += arr[i];
}
avg = (double)sum / size;
return avg;
}
When the above code is compiled and executed, it produces the following results:
Average value is: 214.40000other extensions