C++ int double float对应的长度以及二进制

#include <iostream>

using namespace std;

void showIntBit(int a);
void showDoubleBit(double a1);
void showFloatBit(float a1);

int main()
{
    int a1 = 20;
    double a2 = 20.0;
    float a3 = 20.0f;

    cout << "" << sizeof(a1) <<"  "<<sizeof(a2)<< "  "<<sizeof(a3)<<endl;
    showIntBit(a1);
    showDoubleBit(a2);
    showFloatBit(a3);

    system("pause");
    return 0;
}

//按位置取元素判断 int 4个字节，char 1个字节， 1个字节8位 
void showIntBit(int a1) {
    char *c1 = (char *)&a1;
    char byte1;
    int len1 = 0;
    if (a1 <= 255)
    {
        len1 = 1;
    }
    else if (a1 > 255 && a1 <= 65535)
    {
        len1 = 2;
    }
    else if (a1 > 65535 && a1 < 16777215)
    {
        len1 = 3;
    }
    else
    {
        len1 = 4;
    }

    for (int i = 0; i<len1; i++) 
    {
        byte1 = *c1;
        for (int j = 0; j<8; j++) 
        {
            if (0b10000000 & byte1)
            {
                cout << "1";
            }
            else
            {
                cout << "0";
            }
            byte1 = byte1 << 1;
        }
        cout << " ";
        c1++;
    }
    cout << endl;
}

void showDoubleBit(double val1)
{
    unsigned idx;
    unsigned char arr[sizeof val1];

    memcpy(arr, &val1, sizeof val1);

    for (idx = CHAR_BIT * sizeof val1; idx--; ) 
    {
        putc(
            (arr[idx / CHAR_BIT] & (1u << (idx%CHAR_BIT)))
            ? '1'
            : '0'
            , stdout
        );
    }

    cout << endl;
}

void showFloatBit(float val1) {
    unsigned idx;
    unsigned char arr[sizeof val1];

    memcpy(arr, &val1, sizeof val1);

    for (idx = CHAR_BIT * sizeof val1; idx--; )
    {
        putc(
            (arr[idx / CHAR_BIT] & (1u << (idx%CHAR_BIT)))
            ? '1'
            : '0'
            , stdout
        );
    }

    cout << endl;
}

4 8 4
00010100
0100000000110100000000000000000000000000000000000000000000000000
01000001101000000000000000000000
请按任意键继续. . .