将十进制转换成二进制输出

以下代码使用四种方式实现了转换输出的功能：

1、运用“除2求余”的方法；

2、运用位运算的方式（不太明白为什么？），而且是倒序输出；

3、也是运用位运算，容易理解，但是输出零太多了：（

4、同上，输出做了处理：）

// L11_1.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <math.h>
#include <iostream>
using namespace std;


void ToIntBinary(int nNum);//it is for integer;
void ToDecimalBinary(float nNum);//it is for decimal data;



int main(int argc, char* argv[])
{
    //No1.using math
    float fDecNum;
    int nDecNum;
   
    cout << "Please input a unsigned number:";
    cin >>fDecNum;

    cout <<"The Number "<<fDecNum<<" into binary is:";
    //whether the number is unsigned?only integer?
    if (fDecNum<0)
    {
        cout<<"-";
        fDecNum=abs(fDecNum);
    }
    if (!(fDecNum-(int)fDecNum))
    {
        ToIntBinary(fDecNum);
    }
    else
    {
        ToIntBinary((int)fDecNum);
        cout<<".";
        ToDecimalBinary(fDecNum);

    }
   
    cout <<'/n';

    //No.2 using Bit arithmetic
    cout << "Please input a unsigned integer number:";
    cin>>nDecNum;
    cout <<"The Number "<<nDecNum<<" into binary is:";
    while( nDecNum )
    {
        //change into binary (negative sequence)
        cout<<(!(( nDecNum ^ (nDecNum-1))&(nDecNum-1)));    
        nDecNum = nDecNum >> 1;
    }
    cout<<endl;

   
    //No.3  using Bit arithmetic
    cout << "Please input a unsigned integer number:";
    cin>>nDecNum;
    cout <<"The Number "<<nDecNum<<" into binary is:";
    //because integer have 4 bytes,so it have 32 bits;
    //if int nMask=0x80000000,the result is not correct!
    //if use "int",the highest position must be '0';
    unsigned int unMask=0x80000000;//or int nMast=0x40000000;   
    int nBit;
    //the result of following have more '0'
    for(int i=0;i<32;i++)
    {
        nBit=(nDecNum & unMask)?1:0;
        cout<<nBit;
        //equal to nMask/2,move to next,getting the next mask word
        unMask=unMask>>1;
    }
    cout<<endl;

   
    //No.4 using Bit arithmetic
    //the result of following looks better
    cout << "Please input a unsigned integer number:";
    cin>>nDecNum;
    cout <<"The Number "<<nDecNum<<" into binary is:";
    int nMask=0x40000000;
    int nBitAnother;
    while(nMask)
    {
        nBitAnother=(nDecNum & nMask)?1:0;
        if (nBitAnother)
        {
            break;
        }
        nMask=nMask>>1;
    }
    while(nMask)
    {
       
        nBitAnother=(nDecNum & nMask)?1:0;
        nMask=nMask>>1;
        cout<<nBitAnother;
    }
    cout<<endl;


    return 0;
}



void ToIntBinary(int nNum)
{
    if(nNum==0)
    {
        cout <<"0";
    }
    else
        if(nNum==1)
        {
            cout <<"1";
        }
        else
        {
//            ToIntBinary(nNum/2);//using recursion
            ToIntBinary(nNum>>1);//same as the up;
           
            cout << nNum%2;
        }
}


void ToDecimalBinary(float nNum)
{
    nNum=nNum-(int)nNum;   
    while(nNum)
    {
        nNum*=2;//equal to nNum=nNum<<1,but only with integer;

        cout<<(int)nNum;
        nNum=nNum-(int)nNum;

    }
   
}