# C 程序：將八進制數轉換為十進制數 > 原文： [https://beginnersbook.com/2017/09/c-program-to-convert-octal-number-to-decimal-number/](https://beginnersbook.com/2017/09/c-program-to-convert-octal-number-to-decimal-number/) 該程序將八進制數轉換為等效的十進制數。 ## 示例：將八進制轉換為十進制的程序 在這個程序中，我們為八進制到十進制轉換創建了一個用戶定義的函數。程序將八進制數（由用戶輸入）作為輸入，并使用函數將其轉換為十進制數。要了解此程序，您應該具有以下 [C 編程](https://beginnersbook.com/2014/01/c-tutorial-for-beginners-with-examples/)主題的知識： 1. [C - 用戶自定義函數](https://beginnersbook.com/2014/01/c-functions-examples/) 2. [C `while`循環](https://beginnersbook.com/2014/01/c-while-loop/) ```c #include <stdio.h> #include <math.h> /* This function converts the octal number "octalnum" to the * decimal number and returns it. */ long octalToDecimal(int octalnum) { int decimalnum = 0, temp = 0; while(octalnum != 0) { decimalnum = decimalnum + (octalnum%10) * pow(8,temp); temp++; octalnum = octalnum / 10; } return decimalnum; } int main() { int octalnum; printf("Enter an octal number: "); scanf("%d", &octalnum); printf("Equivalent decimal number is: %ld", octalToDecimal(octalnum)); return 0; } ``` 輸出： ```c Enter an octal number: 754 Equivalent decimal number is: 492 ``` 看看這些相關的 C 程序： 1. [C 程序：將八進制轉換為二進制](https://beginnersbook.com/2017/09/c-program-to-convert-octal-number-to-binary-number/) 2. [C 程序：將二進制轉換為八進制](https://beginnersbook.com/2017/09/c-program-to-convert-binary-to-octal-number-system/) 3. [C 程序：將二進制轉換為十進制](https://beginnersbook.com/2015/02/c-program-to-convert-binary-number-to-decimal-number/) 4. [C 程序：將小寫字符串轉換為大寫](https://beginnersbook.com/2015/02/c-program-to-convert-lowercase-string-to-uppercase-string/) 5. [C 程序：將大寫字符串轉換為小寫](https://beginnersbook.com/2015/02/c-program-to-convert-uppercase-string-to-lowercase-string/)