What does sizeof mean in c++

The sizeof operator is used in C to get the byte size of a data type, returning an integer of type size_t. It can be applied to basic types, user-defined types and pointer types, and can be used to optimize memory usage and improve code efficiency.

The meaning of sizeof in C

sizeof is an operator in C that is used to determine the data type size in bytes.

Function

The sizeof operator returns the size in bytes of a specific data type. It can be applied to basic types (such as int, float), user-defined types (such as classes, structures) and pointer types.

Syntax

sizeof(data_type);

Where:

• data_type is the data type to be determined.

Return type

The sizeof operator returns an integer of type size_t, which represents the byte size of the data type.

Example

int main() {
    int x;
    double y;
    struct Point {
        int x;
        int y;
    };
    Point point;

    // 输出基本类型的字节大小
    std::cout << sizeof(int) << std::endl;  // 输出 4
    std::cout << sizeof(double) << std::endl;  // 输出 8

    // 输出用户自定义类型的字节大小
    std::cout << sizeof(Point) << std::endl;  // 输出 8

    return 0;
}

Output:

<code>4
8
8</code>

Notes

• sizeof operator returns is the memory footprint of the data type, excluding alignment bytes.
• The sizeof operator can be applied to variables, functions, arrays, and pointers.
• The sizeof operator can be used to optimize memory usage and improve code efficiency.

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