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Callbacks in C

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  • Difficulty Level : Medium
  • Last Updated : 05 Mar, 2019
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A callback is any executable code that is passed as an argument to other code, which is expected to call back (execute) the argument at a given time [Source : Wiki]. In simple language, If a reference of a function is passed to another function as an argument to call it, then it will be called as a Callback function.

In C, a callback function is a function that is called through a function pointer.

Below is a simple example in C to illustrate the above definition to make it more clear:




// A simple C program to demonstrate callback
#include<stdio.h>
  
void A()
{
    printf("I am function A\n");
}
  
// callback function
void B(void (*ptr)())
{
    (*ptr) (); // callback to A
}
  
int main()
{
    void (*ptr)() = &A;
      
    // calling function B and passing
    // address of the function A as argument
    B(ptr);
  
   return 0;
}

I am function A

In C++ STL, functors are also used for this purpose.

This article is contributed by Ranju Kumari. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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