Dark Horse Programmer-C language Pointer learning

The difficulty and essence of C language is the pointer, the ability to fully understand the pointer and use it skillfully is not an easy thing, there are a few points of knowledge more around.

1. The difference between an array pointer and an array of pointers.

An array pointer is a pointer to a pointer to an array, just like a int*,char* pointer, except that it is an array (the first element) with a size of 4 (under a 32-bit platform) that can be used to find the entire array.

1#include <stdio.h>2 intMainintargcChar*argv[])3 {4     inta[3][4] = {{0,1,2,4},5{5,6,7,8},6{9,Ten, One, A}};7     int(*p) [4];8p =A;9printf"%d", * * (P +1)) ;Ten     return 0; One}

where int (*p) [4] is a two-dimensional array pointer.

And the pointer array is an array, the elements of the array are pointers only, see the following code

1#include <stdio.h>2 intMainintargcChar*argv[])3 {4     inta[3][4] = {{0,1,2,4},5{5,6,7,8},6{9,Ten, One, A}};7   　　 int*p[3];8   　　  for(intI=0;i<3; i++){9P[i] =A[i];Ten  } Oneprintf"%d", *p[1]) ; A   　　 return 0; -}

int *p[3] There are pointers.

2. The difference between pointer function and function pointer

A pointer function is a function whose return value is a pointer. In fact, there is no pointer function to say that only the return value is a function of a pointer or a function that is a pointer to a parameter.

A function pointer is a pointer to a specific function. It is very useful in programming, can significantly reduce the amount of code and optimize the code structure , here is a simple usage example.

1#include"stdio.h"2 3 #defineOK 14 5 intFUN1 (intnum)6 {7printf"The Fun1 value is%d\n", num);8     returnOK;9 } Ten  One intFun2 (intnum) A { -printf"The Fun2 value is%d\n", num); -     returnOK; the }  -  - intFUN3 (intnum) - { +printf"The Fun3 value is%d\n", num); -     returnOK; + }  A  at  - intMain () - {    -     inti,state; -     //Defining function Pointers -     int(*fun_p[3])(intnum);  in     //Initializing function Pointers -fun_p[0] =Fun1;  tofun_p[1] =Fun2; +fun_p[2] =Fun3; -      the      for(i=0;i<3; i++) *State =Fun_p[i] (i); $ GetChar ();Panax Notoginseng     return ; -}

Dark Horse Programmer-C language Pointer learning