C语言进阶课程学习记录-第29课 - 指针和数组分析（下）

本文学习自狄泰软件学院 唐佐林老师的 C语言进阶课程，图片全部来源于课程PPT，仅用于个人学习记录

数组名与指针

实验-数组形式转换

#include <stdio.h>int main()
{int a[5] = {0};int* p = a;int i = 0;for(i=0; i<5; i++){p[i] = i + 1;}for(i=0; i<5; i++){printf("a[%d] = %d\n", i, *(a + i));}printf("\n");for(i=0; i<5; i++){i[a] = i + 10;//可行 }for(i=0; i<5; i++){printf("p[%d] = %d\n", i, p[i]);}return 0;
}/*
output:
a[0] = 1
a[1] = 2
a[2] = 3
a[3] = 4
a[4] = 5p[0] = 10
p[1] = 11
p[2] = 12
p[3] = 13
p[4] = 14用指针+下标代替数组赋值，可行*/

实验-数组名与指针的差异

//ext.c
int a[] = {1, 2, 3, 4, 5};

#include <stdio.h>int main()
{// extern int a[];//case1/*output:&a = 00402000 //数组地址a = 00402000  //首元素地址*a = 1*/extern int *a;//case2/*output:&a = 00402000a = 00000001*/printf("&a = %p\n", &a);//printf("a = %p\n", a);//1printf("*a = %d\n", *a);//访问地址00000001 报错return 0;
}

实验-转化后数组名加一的比较

#include <stdio.h>int main()
{int a[5] = {1, 2, 3, 4, 5};int* p1 = (int*)(&a + 1);int* p2 = (int*)((int)a + 1);int* p3 = (int*)(a + 1);printf("%d, %d, %d\n", p1[-1], p2[0], p3[1]);return 0;
}/*output:小端 数据低位放在低地址中01 00 00  00    02 00 00  00     03 00 00  00    04 00 00  00     05 00 00  005    33554432  3*/

实验-数组名作为函数形参

#include <stdio.h>void func1(char a[5])
{printf("In func1: sizeof(a) = %d\n", sizeof(a));*a = 'a';a = NULL;
}void func2(char b[])
{printf("In func2: sizeof(b) = %d\n", sizeof(b));*b = 'b';b = NULL;
}int main()
{char array[10] = {0};func1(array);printf("array[0] = %c\n", array[0]);func2(array);printf("array[0] = %c\n", array[0]);return 0;
}/*output:
In func1: sizeof(a) = 4
array[0] = a
In func2: sizeof(b) = 4
array[0] = b
数组名作为函数形参会退化为指针*/

小结

数组名与指针仅使用方式相同
数组名的本质不是指针；指针的本质不是数组
数组名并不是数组的地址，而是数组首元素的地址
函数的数组参数退化为指针