# C++ 程序：將二進制數轉換為八進制，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，您將學習通過創建用戶定義的函數將二進制數轉換為八進制，以及將八進制數手動轉換為二進制。 要理解此示例，您應該了解以下 [C++ 編程](/cpp-programming "C++ tutorial")主題： * [C++ 函數](/cpp-programming/function) * [C++ 中用戶定義函數的類型](/cpp-programming/user-defined-function-types) * [C++ `if`，`if...else`和嵌套`if...else`](/cpp-programming/if-else) * [C++ `while`和`do...while`循環](/cpp-programming/do-while-loop) * * * * * * ## 示例 1：將二進制轉換為八進制的程序 在此程序中，我們將首先將二進制數字轉換為十進制。 然后，十進制數字轉換為八進制。 ```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; } ``` **輸出** ```cpp Enter a binary number: 10001 10001 in binary = 21 in octal ``` 用戶輸入的二進制數將傳遞給`convertBinaryToOctal()`函數。 并且，此函數將數字轉換為八進制并返回到`main()`函數 * * * ## 示例 2：將八進制轉換為二進制的程序 在此程序中，八進制數首先轉換為十進制。 然后，將十進制數轉換為二進制數。 ```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; } ``` **輸出** ```cpp Enter an octal number: 54 54 in octal = 101100 ``` 用戶輸入的八進制數字將傳遞給`convertOctalToBinary()`函數。 并且，此函數將數字轉換為二進制并返回`main()`函數