C语言字符型、整型和变量的长度

C语言通过使用sizeof运算符，可以判断出包括char型在内的所有数据类型的长度。

#include <stdio.h>
int main(void) {
  printf("zizeof(char)  = %u\n", (unsigned)sizeof(char));
  printf("zizeof(short) = %u\n", (unsigned)sizeof(short));
  printf("zizeof(int)   = %u\n", (unsigned)sizeof(int));
  printf("zizeof(long)  = %u\n", (unsigned)sizeof(long));
  return 0;
}

运行结果：

程序的运行结果因编译器和运行环境的不同而不用。但**sizeof(char)**必定为1。
short、int 和 long具有以下关系。
sizeof(short) ≤ sizeof(int) ≤ sizeof(long)
注：根据编译器的不同，也可能三者为同样长度。

#include <stdio.h>
int main(void) {
  int int_a, int_b;
  double double_a, double_b;
  printf("sizeof(int) = %u\n", (unsigned)sizeof(int));
  printf("sizeof(double) = %u\n", (unsigned)sizeof(double));
  printf("sizeof(int) = %u\n", (unsigned)sizeof(int_a));
  printf("sizeof(double) = %u\n", (unsigned)sizeof(double_a));
  printf("sizeof(int + int) = %u\n", (unsigned)sizeof(int_a + int_b));
  printf("sizeof(int + double) = %u\n", (unsigned)sizeof(int_a + double_b));
  printf("sizeof(double + double) = %u\n", (unsigned)sizeof(double_a + double_b));
  return 0;
}

运行结果：