Callbacks in C

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 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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