黑马程序员—C学习笔记—指针字符串与其内存细节

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    本节是个人学习过程中的笔记，供初学者一起学习，欢迎大家批评指正，留言参与讨论，谢谢。    本节涉及到指针字符串和数组字符串的存储等基本问题，涉及很多细节，详细变化请参考代码，谢谢。

#include <stdio.h>#include <string.h>int main(){    char name[]="Jack";    char* name1="Jack";    char* name2="Jack";    char* name3="Jack\0";    char name4[]="Jack\0";    char n1[]={'J','a','c','k'};    char n2[]={'J','a','c','k','\0'};//    char* n3={'J','a','c','k'};这两种做法应该是错误的，指针字符串应该指向字符常量，而右侧字符数组的值是可以改变的//    char* n4={'J','a','c','k','\0'};    //如何把'\0'作为最后一个字符输入数组中呢？放在中间啥效果？    char n5[]={'J','a','\0','k','\0'};    char n6[]={'J','a','\0','c','k'};    printf("name:%s\n",name);  //这5行都输出 jack    printf("name1:%s\n",name1);    printf("name2:%s\n",name2);    printf("name3:%s\n",name3);//默认都不输出\0    printf("name4:%s\n",name4);    printf("n1:%s\n",n1);//输出jackjack ==》n1的定义方法有错，需要写出最后一个\0 否则容易出错    printf("n2:%s\n",n2); //输出jack    //printf("n3:%s\n",n3);输出错误，程序中断    //printf("n4:%s\n",n4);输出错误，程序中断    printf("n5:%s\n",n5); //这两行输出ja  ==》遇到\0就停止输出，printf函数中的%s机制类似strlen函数，都是遇到\0为判断标准    printf("n6:%s\n",n6);//    printf("name:%s\n",name[]);  //这两行错误，不符合语法//    printf("name1:%s\n",name1[]);    printf("sizeof(name)=%zd\n",sizeof(name)); //输出5, jack四个字符+'\0'，输出的是name数组所占空间为5个字节    printf("sizeof(name1)=%zd\n",sizeof(name1));//输出8,name1为指针变量，所占空间为8个字节，如何输出这个字符串所占空间，即为5呢？？    printf("sizeof(name2)=%zd\n",sizeof(name2));//8    printf("sizeof(name3)=%zd\n",sizeof(name3));//8    printf("sizeof(name4)=%zd\n",sizeof(name4));//6    printf("sizeof(\"Jack\")=%zd\n",sizeof("Jack"));//5    printf("sizeof(n1)=%zd\n",sizeof(n1));//4    printf("sizeof(n2)=%zd\n",sizeof(n2));//5//    printf("sizeof(n3)=%zd\n",sizeof(n3));//    printf("sizeof(n4)=%zd\n",sizeof(n4));    printf("sizeof(n5)=%zd\n",sizeof(n5));//5    printf("sizeof(n6)=%zd\n",sizeof(n6));//5    //sizeof()函数，如果是指针类型就输出8，其他只看元素个数说话，不管\0与否，只有char name[]="Jack";这种情况才默认加一个\0，计算成5.    printf("strlen(name)=%zd\n",strlen(name)); //字符串长度，表示元素个数，'\0'不是有效原酸，所以输出都是4，    printf("strlen(name1)=%zd\n",strlen(name1));//这四个都是4    printf("strlen(name2)=%zd\n",strlen(name2));    printf("strlen(name3)=%zd\n",strlen(name3));    printf("strlen(name4)=%zd\n",strlen(name4));    printf("strlen(n1)=%zd\n",strlen(n1));//8    printf("strlen(n2)=%zd\n",strlen(n2));//4    //printf("strlen(n3)=%zd\n",strlen(n3));    //printf("strlen(n4)=%zd\n",strlen(n4));    printf("strlen(n5)=%zd\n",strlen(n5));//2    printf("strlen(n6)=%zd\n",strlen(n6));//2    printf("name[1]=%c\n",name[1]);//四个都是a    printf("name[1]=%c\n",*(name+1));    printf("name1[1]=%c\n",name1[1]);    printf("name1[1]=%c\n",*(name1+1));    printf("address of name = %p\n",name);    printf("address of name1 = %p\n",name1);//name1 name2地址相同    printf("address of name2 = %p\n",name2);// ==》指针字符串，字符串是常量放在静态内存中    printf("address of name3 = %p\n",name3);    printf("address of name4 = %p\n",name4);    printf("address of n1 = %p\n",n1);    printf("address of n2 = %p\n",n2);//    printf("address of n3 = %p\n",n3);  //n3 n4 都输出地址0x4a，应该是报错//    printf("address of n4 = %p\n",n4);    printf("address of n5 = %p\n",n5);    printf("address of n6 = %p\n",n6);    printf("address of \"Jack\" = %p\n",&"jack");//两个jack地址相同，与指针字符串地址又不同。    printf("address of \"Jack\" = %p\n",&"jack");//有无指针指向的字符串常量，也是有区别的。    printf("address of \"Jack\\0\" = %p\n",&"jack\0");}

运行结果如下：