Pointer to function 1
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This document explains function pointers in C, highlighting their definition, motivation for use, declaration, initialization, and how to call them. Function pointers are crucial for implementing features like callback mechanisms and achieving object-oriented programming concepts. It includes examples and demonstrations of using function pointers in practice.
![Example
#include <stdio.h>
#include <stdlib.h>
//function used to add two numbers
int AddTwoNumber(int iData1 ,int iData2)
{
return (iData1 + iData2);
}
int main(int argc, char *argv[])
{
int iRetValue = 0;
//Declaration of function pointer
int (*pfAddTwoNumber)(int,int) = NULL;
//initialise the function pointer
pfAddTwoNumber = AddTwoNumber;
//Calling the function using function pointer
iRetValue = (*pfAddTwoNumber)(10,20);
//display addition of two number
printf("nnAddition of two number = %dnn",iRetValue);
return 0; }](https://image.slidesharecdn.com/pointertofunction1-180225182022/85/Pointer-to-function-1-8-320.jpg)
Pointer to function 1
- 1. Abu Bakr Mohamed Ramadan eng.abubakr@gmail.com
- 2. Content: What is function pointer? Motivation, what is the use cases of function pointer? Declaration of function pointer in c Initialization of function pointer in c Calling a function using the function pointer Example on function pointer Function pointer as arguments
- 3. What is function pointer? A function pointer is one of the most important pointer tools which is often ignored and misunderstood by the people. A function pointer is similar to the other pointers but the only difference is that it points to a function instead of the variable. Unlike normal pointers, a function pointer points to code, not data. Typically a function pointer stores the start of executable code.
- 4. Motivation, what is the use cases of function pointer? Interrupt Vector table is an array of pointers to function (ISR), Callback mechanism in modular layered application, Basic concept in OS and RTOS programing, we can achieve OOP concepts like inheritance and polymorphism in C using function pointers.
- 5. Declaration of function pointer in c int fpData(int); int *fpData(int); int (*fpData)(int); int (*fpData)(char *); int* (*fpData)(char *); int (*fpData)(int, char *);
- 6. Initialization of function pointer in c declaration of function pointer int (* pfAddTwoNumber) (int, int); Initialize the function pointer with the address of AddTwoNumber pfAddTwoNumber = & AddTwoNumber; or pfAddTwoNumber = AddTwoNumber; We can also initialize the function pointer in a single line. int (* pfAddTwoNumber) (int, int) = AddTwoNumber;
- 7. Calling a function using the function pointer First, write the name of a function pointer. pfAddTwoNumber; We know that function pointer is also similar to another pointer but the only difference is that function pointer pointed to a function except for the variable. So we put the * as a prefix to the name of function pointer to take the value of the function pointer. *pfAddTwoNumber; Finally, we have a function. For the function calling just simply add the arguments list with extra parenthesis to the above expression. (*pfAddTwoNumber)(10, 20);
- 8. Example #include <stdio.h> #include <stdlib.h> //function used to add two numbers int AddTwoNumber(int iData1 ,int iData2) { return (iData1 + iData2); } int main(int argc, char *argv[]) { int iRetValue = 0; //Declaration of function pointer int (*pfAddTwoNumber)(int,int) = NULL; //initialise the function pointer pfAddTwoNumber = AddTwoNumber; //Calling the function using function pointer iRetValue = (*pfAddTwoNumber)(10,20); //display addition of two number printf("nnAddition of two number = %dnn",iRetValue); return 0; }
- 9. Function pointer as arguments we can pass the function pointer as an argument into the function like the other pointers. Example on Function pointer as arguments
Editor's Notes
- #6: . It seems like difficult in beginning but once you are familiar with function pointer then it becomes easy. void ( *pfDisplayMessage) (const char *); In above expression, pfDisplayMessage is a pointer to a function taking one argument, const char *, and returns void.