# C 程序：将八进制数转换为二进制数 > 原文： [https://beginnersbook.com/2017/09/c-program-to-convert-octal-number-to-binary-number/](https://beginnersbook.com/2017/09/c-program-to-convert-octal-number-to-binary-number/) 该程序使用用户定义的函数将八进制数转换为二进制数。 ## 示例：将八进制转换为二进制的程序 在这个程序中，我们创建了一个用户定义的函数`octalToBinary()`。此函数首先将八进制数（由用户输入）转换为十进制数，然后将该十进制数转换为二进制数。要了解该程序的工作原理，您应具备以下 [C 编程](https://beginnersbook.com/2014/01/c-tutorial-for-beginners-with-examples/)主题的基本知识： 1. [C 编程循环](https://beginnersbook.com/2014/01/c-while-loop/) 2. [C 编程函数](https://beginnersbook.com/2014/01/c-functions-examples/) ```c #include <stdio.h> #include <math.h> //This function converts octal number to binary number long octalToBinary(int octalnum) { int decimalnum = 0, i = 0; long binarynum = 0; /* This loop converts octal number "octalnum" to the * decimal number "decimalnum" */ while(octalnum != 0) { decimalnum = decimalnum + (octalnum%10) * pow(8,i); i++; octalnum = octalnum / 10; } //i is re-initialized i = 1; /* This loop converts the decimal number "decimalnum" to the binary * number "binarynum" */ while (decimalnum != 0) { binarynum = binarynum + (decimalnum % 2) * i; decimalnum = decimalnum / 2; i = i * 10; } //Returning the binary number that we got from octal number return binarynum; } int main() { int octalnum; printf("Enter an octal number: "); scanf("%d", &octalnum); //Calling the function octaltoBinary printf("Equivalent binary number is: %ld", octalToBinary(octalnum)); return 0; } ``` 输出： ```c Enter an octal number: 71 Equivalent binary number is: 111001 ``` 看看这些相关的 C 程序： 1. [C 程序：将二进制数转换为八进制数](https://beginnersbook.com/2017/09/c-program-to-convert-binary-to-octal-number-system/) 2. [C 程序：将二进制转换为十进制](https://beginnersbook.com/2015/02/c-program-to-convert-binary-number-to-decimal-number/) 3. [C 程序：将十进制转换为八进制数](https://beginnersbook.com/2017/09/c-program-to-convert-decimal-to-octal-number/) 4. [C 程序：将小写字符串转换为大写字符串](https://beginnersbook.com/2015/02/c-program-to-convert-lowercase-string-to-uppercase-string/) 5. [C 程序：将大写字符串转换为小写](https://beginnersbook.com/2015/02/c-program-to-convert-uppercase-string-to-lowercase-string/)