Understanding of c arrays and pointers

1#include <stdio.h>2 3 intMainvoid)4 {5     inta[]={1,2,3,4,5};6     int*p = (int*) (&a +1);7printf"%d,%d\n", *a+1, * (P-1));8 9//int(*PTR1) [5] = &A; √Ten//int(*PTR2) [5] =A; X One//int(*PTR1) [3] = &A; X A//int(*PTR2) [3] =A; X - } -  the //2,5

The array name can only be used as the right value!

When we define an array, the compiler determines the allocated memory size based on the number and type of elements specified. and assign the name of the address to an array name.

A[0], a[1] ... An array element, but not an element name!

Pointers, 32 systems always have a value of 4 bytes (0x11111111) to hold only one address cell, so the first address is always stored.

However, you need to move the pointer according to the type size when you visit.

Array Name: The value is equivalent to the "first address" of the array "first element" (pointer to the first element of the array)

P + 1

Char* moves a byte, int* moves 4 bytes! Array pointer moves an array element type length! The second level pointer moves a pointer length (4)!

&a: Represents an array pointer (pointer to array variable a)

Access to an array, always converted to access to pointers!

Two-dimensional arrays

1 int b[2[2] = {{1,2},{3,4}}; 2 // int *p2 = b;         X3//  Int (*P5) [2] = b;    √4//  int **p      = b;    X

Two-dimensional array name, pointer to the first element b[0], array pointer "one-level pointer"!

1 // int *p3 = b[0];             √2//  Int (*P4) [2][2] = &b;    √

Access to all elements of a two-dimensional array (first-level pointers):

1#include <stdio.h>2 intMain ()3 {4     intiarray[2][3] =        {{1,2,3},{4,5,6}};5     int*parray =NULL;6 7Parray = (int*) IArray;8   9 Tenprintf"array[0][0] =%d\n", *Parray); Oneprintf"array[1][2] =%d\n", * (Parray +5)); Aprintf"array[1][2] =%d\n", * (Parray +1*3+2));/*The array itself is continuously arranged in the address space.*/ -printf"array[1][2] =%d\n", *((int*)(*((int(*) [3]) Parray +1)) +2)); -     return 0; the}

Access to all elements of a two-dimensional array (array pointers):

1#include <stdio.h>2 3 intMain ()4 {5     intiarray[2][3] = {{1,2,3},{4,5,6}};6     int(*parray) [3] = NULL;7    8Parray =IArray;9 Tenprintf"array[0][0] =%d\n", **Parray); Oneprintf"array[1][2] =%d\n", * (* (parray+1)+2)); A     return 0; -}

1 intMain ()2 {3         intiarray[2][3] =        {{1,2,3},{4,5,6}};4 5         int(*parray) [3] =NULL;6 7Parray =IArray;8 9printf"array[0][0] =%d\n", parray[0][0]);Tenprintf"array[1][2] =%d\n", parray[1][2]); One         return 0; A}

Second-level pointers

As a pointer to a pointer, the value pointed to must be a pointer.

1 intMain ()2 {3         intiarray[2][3] =        {{1,2,3},{4,5,6}};4         int*iparray[2] = {iarray[0], iarray[1]};5         int**parray =NULL;6 7Parray =Iparray;8      9printf"array[0][0] =%d\n", parray[0][0]);Tenprintf"array[1][2] =%d\n", parray[1][2]); One       A         return 0; -}

Understanding of c arrays and pointers