#include <stdio.h>
#include <string.h>

void size()
{
    printf("\n**************************\n");

    char *ptr1 = "Hello word";
    char ptr2[] = "Hello word";
    char ptr3[100] = "Hello word";

    printf("sizeof (*ptr1) = %d\n",sizeof (ptr1));		//測量char *ptr的長度
    printf("strlen(*ptr1) = %d\n",strlen(ptr1));		//測量字串的長度
    printf("sizeof (ptr2[]) = %d\n",sizeof (ptr2));
    printf("strlen(*ptr2[]) = %d\n",strlen(ptr2));
    printf("sizeof (ptr3[]) = %d\n",sizeof (ptr3));
    printf("strlen(*ptr3[100]) = %d\n",strlen(ptr3));
    printf("\n");
    
	printf("sizeof (long) = %d\n",sizeof (int));		//測量int型的長度
    printf("sizeof (short) = %d\n",sizeof (short));
	printf("sizeof (long) = %d\n",sizeof (long));
	printf("sizeof (long long) = %d\n",sizeof (long long));
    printf("sizeof (float) = %d\n",sizeof (float));
    printf("sizeof (double) = %d\n",sizeof (double));
	printf("sizeof (char) = %d\n",sizeof (char));


    printf("\n**************************\n");
}

int main()
{
    size();
	
	return 0;
}
 

<span style="font-size:18px;">結果如下</span>

在實際操作中發現，sizeof的書寫格式為：

sizeof（空格）（需要測量的變數名或資料型別）

其中空格可有可無，對變數的測量還可寫成：

sizeof（空格）變數名

測量資料型別時括號不可省略。

由此可見，sizeof並不是一個函式，sizeof是一個運算子。

sizeof與strlen的區別總結為以下幾點：