# C++ 程序：将二进制数转换为八进制，反之亦然 > 原文： [https://www.programiz.com/cpp-programming/examples/octal-binary-convert](https://www.programiz.com/cpp-programming/examples/octal-binary-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八进制，以及将八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++ `if`，`if...else`和嵌套`if...else`](/cpp-programming/if-else) * [C++ `while`和`do...while`循环](/cpp-programming/do-while-loop) * * * * * * ## 示例 1：将二进制转换为八进制的程序 在此程序中，我们将首先将二进制数字转换为十进制。 然后，十进制数字转换为八进制。 ```cpp #include <iostream> #include <cmath> using namespace std; int convertBinarytoOctal(long long); int main() { long long binaryNumber; cout << "Enter a binary number: "; cin >> binaryNumber; cout << binaryNumber << " in binary = " << convertBinarytoOctal(binaryNumber) << " in octal "; return 0; } int convertBinarytoOctal(long long binaryNumber) { int octalNumber = 0, decimalNumber = 0, i = 0; while(binaryNumber != 0) { decimalNumber += (binaryNumber%10) * pow(2,i); ++i; binaryNumber/=10; } i = 1; while (decimalNumber != 0) { octalNumber += (decimalNumber % 8) * i; decimalNumber /= 8; i *= 10; } return octalNumber; } ``` **输出** ```cpp Enter a binary number: 10001 10001 in binary = 21 in octal ``` 用户输入的二进制数将传递给`convertBinaryToOctal()`函数。 并且，此函数将数字转换为八进制并返回到`main()`函数 * * * ## 示例 2：将八进制转换为二进制的程序 在此程序中，八进制数首先转换为十进制。 然后，将十进制数转换为二进制数。 ```cpp #include <iostream> #include <cmath> using namespace std; long long convertOctalToBinary(int); int main() { int octalNumber; cout << "Enter an octal number: "; cin >> octalNumber; cout << octalNumber << " in octal = " << convertOctalToBinary(octalNumber) << "in binary"; return 0; } long long convertOctalToBinary(int octalNumber) { int decimalNumber = 0, i = 0; long long binaryNumber = 0; while(octalNumber != 0) { decimalNumber += (octalNumber%10) * pow(8,i); ++i; octalNumber/=10; } i = 1; while (decimalNumber != 0) { binaryNumber += (decimalNumber % 2) * i; decimalNumber /= 2; i *= 10; } return binaryNumber; } ``` **输出** ```cpp Enter an octal number: 54 54 in octal = 101100 ``` 用户输入的八进制数字将传递给`convertOctalToBinary()`函数。 并且，此函数将数字转换为二进制并返回`main()`函数