# C++ 程序：将二进制数转换为十进制，反之亦然

> 原文： [https://www.programiz.com/cpp-programming/examples/binary-decimal-convert](https://www.programiz.com/cpp-programming/examples/binary-decimal-convert)

#### 在此示例中，您将学习通过创建用户定义的函数将二进制数转换为十进制，以及将十进制数手动转换为二进制。

要理解此示例，您应该了解以下 [C++ 编程](/cpp-programming "C++ tutorial")主题：

*   [C++ 函数](/cpp-programming/function)
*   [C++ 中用户定义函数的类型](/cpp-programming/user-defined-function-types)
*   [C++ 递归](/cpp-programming/recursion)
*   [C++ `if`，`if...else`和嵌套`if...else`](/cpp-programming/if-else)
*   [C++ `while`和`do...while`循环](/cpp-programming/do-while-loop)

* * *

访问此页面以了解[如何将二进制数转换为十进制](http://www.wikihow.com/Convert-from-Binary-to-Decimal "Binary number to Decimal")。

## 示例 1：将二进制数转换为十进制

```cpp
#include <iostream>
#include <cmath>

using namespace std;

int convertBinaryToDecimal(long long);

int main()
{
    long long n;

    cout << "Enter a binary number: ";
    cin >> n;

    cout << n << " in binary = " << convertBinaryToDecimal(n) << "in decimal";
    return 0;
}

int convertBinaryToDecimal(long long n)
{
    int decimalNumber = 0, i = 0, remainder;
    while (n!=0)
    {
        remainder = n%10;
        n /= 10;
        decimalNumber += remainder*pow(2,i);
        ++i;
    }
    return decimalNumber;
} 
```

**输出**

```cpp
Enter a binary number: 1111
1111 in binary = 15 
```

访问此页面以了解[如何将十进制数转换为二进制](http://www.wikihow.com/Convert-from-Decimal-to-Binary "Binary number to Decimal")。

## 示例 2：将十进制数转换为二进制

```cpp
#include <iostream>
#include <cmath>
using namespace std;

long long convertDecimalToBinary(int);

int main()
{
    int n, binaryNumber;

    cout << "Enter a decimal number: ";
    cin >> n;
    binaryNumber = convertDecimalToBinary(n);
    cout << n << " in decimal = " << binaryNumber << " in binary" << endl ;
    return 0;
}

long long convertDecimalToBinary(int n)
{
    long long binaryNumber = 0;
    int remainder, i = 1, step = 1;

    while (n!=0)
    {
        remainder = n%2;
        cout << "Step " << step++ << ": " << n << "/2, Remainder = " << remainder << ", Quotient = " << n/2 << endl;
        n /= 2;
        binaryNumber += remainder*i;
        i *= 10;
    }
    return binaryNumber;
}
```

**输出**

```cpp
Enter a decimal number: 19
Step 1: 19/2, Remainder = 1, Quotient = 9
Step 2: 9/2, Remainder = 1, Quotient = 4
Step 3: 4/2, Remainder = 0, Quotient = 2
Step 4: 2/2, Remainder = 0, Quotient = 1
Step 5: 1/2, Remainder = 1, Quotient = 0
19 in decimal = 10011 in binary
```