How to use sizeof in c language

sizeof Usage in C

sizeof is an operator used to determine the number of bytes that a data type or variable occupies in memory. It is a unary operator, and the parentheses can be data types or variable names.

Syntax:

<code>sizeof(数据类型/变量名)</code>

Usage:

• Get the size of the data type:

int i;
printf("int 的大小：%d 字节\n", sizeof(int));

• Get the size of the variable:

int array[10];
printf("array 的大小：%d 字节\n", sizeof(array));

• Get the size of the pointer variable:

int *ptr;
printf("ptr 的大小：%d 字节\n", sizeof(ptr));

• Get the size of the structure or union:

struct person {
    char name[20];
    int age;
};

printf("person 结构体的大小：%d 字节\n", sizeof(struct person));

• Get the size of the array element type:

int array[10];
printf("array 元素类型的大小：%d 字节\n", sizeof(array[0]));

Note:

• sizeof operator returns a compile-time constant, not a run-time constant value. The
• sizeof operator cannot be used to obtain the length of an array. The
• sizeof operator cannot be used to obtain the size of a pointer variable to an array.

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