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C语言各种类型变量初始化     所属分类 c 浏览量 55
全局 和 静态变量会自动初始化为零值
局部变量需要显示初始化,否则值不确定

定义时初始化 


int    i  = 0;
float  f = 0.00f;
double d = 0.00;
char ch = '\0'; 
char str[10] = "";

char str[10];
memset(str, 0, sizeof(str));

memset 按字节进行填充 注意是按字节填充

int num;
memset(&num, 0, sizeof(int));
printf("step1=%d\n", num);
memset(&num, 1, sizeof(int));
printf("step2=%d\n", num);

step1 = 0
step2 = 16843009

int  4个字节
00000000 00000000 00000000 00000000
00000001 00000001 00000001 00000001

char year[4+1];
memset(year, 0, sizeof(year));
strcpy(year,"2021");

指针一般初始化为 NULL 

int *pnum = NULL;
int num = 0;
pnum = &num ;

typedef struct student
{
 int id;
 char name[20];
}Student;
Student student1;
memset((char *)&student1, 0, sizeof(student1));



https://gitee.com/dyyx/hellocode/blob/master/web/tech/c/demo/init.c #include<stdio.h> #include<stdlib.h> #include <string.h> typedef struct student { int id; char name[20]; }Student; int main(int argc,char *argv[]){ int i = 0; float f = 0.00f; double d = 0.00; char ch = '\0'; char str[3] = ""; char str2[] = "hello"; char str3[7]; memset(str3, 0, sizeof(str3)); char str4[7]={0}; int num; memset(&num, 0, sizeof(int)); printf("step1=%d\n", num); memset(&num, 1, sizeof(int)); // 16843009 // memset 按字节填充 // 00000001 00000001 00000001 00000001 printf("step2=%d\n", num); char year[4+1]; memset(year, 0, sizeof(year)); strcpy(year,"2021"); printf("year=%s\n",year); int *pnum = NULL; pnum = &num ; printf("%p\n",pnum); Student student1; memset((char *)&student1, 0, sizeof(student1)); printf("id=%d, name=%s\n", student1.id,student1.name); Student student2={0}; printf("id=%d, name=%s\n", student2.id,student2.name); }

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