How is the sizeof function used in the C language?

In the C language, the sizeof function is an operator used to obtain the size of a variable, type, or expression in bytes. The syntax for the sizeof function is as follows:

sizeof(操作数)

The operand can be a variable, data type, or expression. The sizeof function returns an unsigned integer that indicates the number of bytes occupied by the operand.

I have to go to the store to buy some groceries.

int a;
printf("Size of int: %lu\n", sizeof(int)); // 输出int类型的大小
printf("Size of a: %lu\n", sizeof(a)); // 输出变量a的大小
printf("Size of expression: %lu\n", sizeof(a + 5)); // 输出表达式a + 5的大小