# C 程序：将二进制数转换为八进制，反之亦然 > 原文： [https://www.programiz.com/c-programming/examples/octal-binary-convert](https://www.programiz.com/c-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来将二进制数手动转换为八进制，反之亦然。 要理解此示例，您应该了解以下 [C 编程](/c-programming "C tutorial")主题： * [C 函数](/c-programming/c-functions) * [C 用户定义的函数](/c-programming/c-user-defined-functions) * * * ## 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。 ```c #include <math.h> #include <stdio.h> int convert(long long bin); int main() { long long bin; printf("Enter a binary number: "); scanf("%lld", &bin); printf("%lld in binary = %d in octal", bin, convert(bin)); return 0; } int convert(long long bin) { int oct = 0, dec = 0, i = 0; // converting binary to decimal while (bin != 0) { dec += (bin % 10) * pow(2, i); ++i; bin /= 10; } i = 1; // converting to decimal to octal while (dec != 0) { oct += (dec % 8) * i; dec /= 8; i *= 10; } return oct; } ``` **输出** ```c Enter a binary number: 101001 101001 in binary = 51 in octal ``` * * * ## 将八进制转换为二进制的程序 在此程序中，八进制数首先会转换为十进制。 然后，将十进制数转换为二进制数。 ```c #include <math.h> #include <stdio.h> long long convert(int oct); int main() { int oct; printf("Enter an octal number: "); scanf("%d", &oct); printf("%d in octal = %lld in binary", oct, convert(oct)); return 0; } long long convert(int oct) { int dec = 0, i = 0; long long bin = 0; // converting octal to decimal while (oct != 0) { dec += (oct % 10) * pow(8, i); ++i; oct /= 10; } i = 1; // converting decimal to binary while (dec != 0) { bin += (dec % 2) * i; dec /= 2; i *= 10; } return bin; } ``` **输出** ```c Enter an octal number: 67 67 in octal = 110111 in binary ```