Pointers

Function Pointer

• A function pointer is a pointer in which we can store address of a function.
• A function pointer can be defined by using syntax:

• A function Pointer can contains address of a function.
• Address of a function can be find out by using addressof operator.

• If a function pointer contains address of function in it then such a function can be called by using that pointer.

  #include<stdio.h>
  void display(int n)
  {
    int i;
    for(i=1;i<=n;i++)
        printf("%d ",i);
  }
  int max(int a,int b)
  {
    if(a>b)
        return a;
    else
        return b;
  }
  void main()
  {
    int z;
    void (*p1)(int);
    int (*p2)(int,int);
    int (*p3)(int,int);
    p1=&display;
    p2=&max;
    p3=&min;
    //display(15);
    (*p1)(15);
    //z=max(4117,3012);
    z=(*p2)(4117,3012);
    printf("\nGreatest no is %d",z);
    //z=min(4117,3012);
    z=(*p3)(4117,3012);
    printf("\nLowest no is %d",z);
  }

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Greatest no is 4117
Lowest no is 3012
  

Declaration expressions

• int a;
Syntax
datatype name;
• variable of type int
• int a[ ];
Syntax
datatype name[ ];
• an array of type int
• int a[10];
Syntax
datatype name[n];
• an array of type int of size 10
• int *p;
Syntax
datatype * name;
• a pointer of type int
• int * p[10];
Syntax
datatype * name[n];
• an array of pointer which can store address of 10 variables of type int
• int f(int , int );
Syntax
datatype name (datatype of args);
• A function decleration of name 'f' whose return type is int and accepts 2 arguments of type int.
• int f(int* , int* );
Syntax
datatype name( datatype of args);
• A function decleration of name 'f' whose return type is void and accepts 2 arguments of type int pointer.
• int* f( int *, int * );
Syntax
datatype name( datatype of args);
• A function decleration of name 'f' whose return type is int pointer and accepts 2 arguments of type int pointer.
• int **p;
Syntax
datatype **name;
• A pointer to pointer in which we can store address of int pointer.
• int ( * p )[ 10 ];
Syntax
datatype ( * name)[ n];
• a pointer to an int array which can store address of an array of size 10.
• int ( * p )( int , int );
Syntax
datatype (*name)( datatype of args) ;
• A function pointer in which we can store address of function returning a int value & accepting 2 int args.
• int ( * p[ 3 ] ) ( int );
Syntax
datatype (*name [n])( datatype of args);
• An array of function pointer of size 3 in which we can store address of function returning an int value & accepting 1 int args.