C Function Pointer
A function pointer is a pointer that contains the address of a function. It can be declared in following way. You must follow the same syntax for declaration otherwise you will get an error.
Syntax
return_type (* pointer_name) (argument_list);
Example
int (*p) (int, int);
In above example we are declaring a pointer to function or a function pointer that will contain the address of a function with return type integer and having two integer arguments.
The above function pointer p can be assigned address of a function and can call that function in following way. Lets assume the function with name fun1().
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//storing address of function in the function pointer p p = fun1; //first way p = &fun1 //second way //calling the function using function pointer p int c = (*p)(2,3); //first way int c = p(2,3); //second way |
As you can see in above example that function pointer can be assigned address and can call a function in two ways. You can use any one of them.
Lets make one program that will calculate addition of two numbers using the concept of function pointer in C.
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#include<stdio.h> int add(int a,int b) { return a+b; } void main() { int (*p)(int,int); p=&add; printf("Sum=%dn",(*p)(5,3)); } |
Output
Explanation
1. Firstly I have made a function add() that will take two integer arguments, calculate their addition and return the result.
2. Now in the main() function I am declaring a function pointer p and then storing the address of function add(). This can be done without using the address of operator i.e. &.
3. Finally I am calling the function using the function pointer and then displaying the result. As I have already mentioned above that the calling can also be done in two ways. So here we can call the function by simply writing p(5,3).
Below I have added a video that will help you in understanding the concept of function pointer or pointer to function in C.
C function pointer is an advance topic of pointer and a little bit difficult too. If you have any kind of queries then please mention it in comments.
//storing address of function in the function pointer p
p = fun1; //first way
p = &fun1 //second way
but in the next example, it was stored like given below
p=&add;// is this is the third way of storing?