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Callbacks in C

  • Difficulty Level : Medium
  • Last Updated : 05 Mar, 2019

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
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
   return 0;
I am function A

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

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Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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