【C语言笔记】变量的初始值是？

#include <stdio.h>

int a1, a2;
float b1, b2;
char c1, c2;

int main(void)
{
 int a3, a4;
 float b3, b4;
 char c3, c4;

 printf("全局变量：a1 = %d, a2 = %d, b1 = %f, b2 = %f, c1 =%d, c2 =%d\n", a1, a2, b1, b2, c1, c2);
 printf("局部变量：a3 = %d, a4 = %d, b3 = %f, b4 = %f, c3 =%d, c4 =%d\n", a3, a4, b3, b4, c3, c4);

 return 0;
}

全局变量：a1 = 0, a2 = 0, b1 = 0.000000, b2 = 0.000000, c1 =0, c2 =0
局部变量：a3 = 4200660, a4 = 4200754, b3 = 0.000000, b4 = 0.000000, c3 =0, c4 =0