Linux C Program (TEN)

Pointer arrays and level two pointers

1#include <stdio.h>2 3 intMain () {4         inta[5] = {1,3,5,7,9};5         int*p[5], I;6         int**PP =p;7     //point the P pointer array to each a8          for(i =0; I <5; i++){9P[i] =&A[i];Ten         } One     //"" Priority is higher than *, * (P[i]) p[i] = &a[i],so==> *p[i] = *&a[i] = A[i] A          for(i =0; I <5; i++){ -printf"%d",*p[i]); -         } theprintf"\ n"); -     //p and PP are all level two pointers, i=0, *pp=p[0], p[0]=&a[i],*pp=a[0]. -     //after the pp++ is executed, pp points to p[1],*pp=p[1],p[1]=&a[1]. -          for(i =0; I <5; i++,pp++){ +printf"%d",**pp); -         } +      A         return 0 ; at } - Output: - 1 3 5 7 9 - 1 3 5 7 9

The relationship of pointers to arrays

1Nclude<stdio.h>2 3 intMain () {4         inta[2][5] = {1,3,5,7,9,2,4,6,8,Ten};5         //indicates that P is a pointer to a one-dimensional array containing five elements6         int(*p) [5],i;7         //p points to the first row of a two-dimensional array8p =A;9     //after P=a, p=&a, *p = a[1].Ten     //p is an array pointer One          for(i =0; I <5; i++){ Aprintf"%d",(*p) [i]); -         //(*P) [i] is the first to take the contents of P as the starting address of the array, and then go to the first element.  -         //*p[i] is the first element that takes p as the starting address, which is a pointer and then takes the contents of the pointer.  the         } -printf"\ n"); -     //p move to the second row -p++; +          for(i =0; I <5; i++){ -printf"%d",(*2) [i]); +         } Aprintf"\ n"); at  -         return 0; - } -  - int(*p) [5] ；//A pointer - int*p[5]  ;//An array of five elements with a length of 5, with each element in the array pointing to an integer variable. 

Functions and pointers
1. Pointers as Function parameters
The function is to transfer the address of a variable into a function.

1#include <stdio.h>2 voidChangeintIint*p) {3i++;4         if(P! =NULL) {5(*p) + +;//find variable b,b+1 by address6         }7 }8 intMain () {9         intA =5, B =Ten ;TenChange (a,&b); Oneprintf"a=%d,b=%d", A, b); A         return 0; -}

2. return pointer to function
1 int *f ( int i, int j);
() has a higher priority than *
Indicates that f is a function with a pointer to the function name, indicating that the function has a return value type of pointer.

1Include<stdio.h>2 //defines a pointer array named name, with each array element pointing to a string3 Char*name[7] = {"Monday","Tuesday","Wednessday","Thursday","Friday","Saturday","Sunday"};4 //defines a pointer that points to a string5 Char*message ="wrong input";6 //functions that return pointers7 Char*week (intDay ) {8         if(Day <0|| Day >7){9                 returnmessage;Ten}Else{ One                 returnname[day-1] ; A         } - } -  the  - intMain () { -         intDay ; -         Char*p; +  -printf"input a number of a week:\n"); +scanf"%d",&Day ); A      atp =Week (day); -printf"%s\n", p); -  -         return 0; -}

3. Pointer to function 87 page----------

Linux C Program (TEN)