The ﬁrst operand must be a function pointer (a function designator is also acceptable because it will be converted to a pointer to the function), identifying the function to call, and all other operands, if any, are collectively known as the function call's arguments. Evaluates into the return value resulting from calling the appropriate function with the respective arguments.
int myFunction(int x, int y)
return x * 2 + y;
int (*fn)(int, int) = &myFunction;
int x = 42; int y = 123;
printf("(*fn)(%i, %i) = %i\n", x, y, (*fn)(x, y)); /* Outputs "fn(42, 123) = 207". */
printf("fn(%i, %i) = %i\n", x, y, fn(x, y)); /* Another form: you don't need to dereference explicitly */