# C 程序：使用函數顯示區間內的質數 > 原文： [https://www.programiz.com/c-programming/examples/prime-interval-function](https://www.programiz.com/c-programming/examples/prime-interval-function) #### 在此示例中，您將學習如何打印兩個數字之間的所有質數（由用戶輸入）。 要理解此示例，您應該了解以下 [C 編程](/c-programming "C tutorial")主題： * [C `for`循環](/c-programming/c-for-loop) * [C `break`和`continue`](/c-programming/c-break-continue-statement) * [C 函數](/c-programming/c-functions) * [C 用戶定義的函數](/c-programming/c-user-defined-functions) * * * 為了找到兩個整數之間的所有質數，創建了`checkPrimeNumber()`。 此函數[檢查數字是否為質數](https://www.programiz.com/c-programming/examples/prime-number)。 * * * ## 兩個整數之間的質數 ```c #include <stdio.h> int checkPrimeNumber(int n); int main() { int n1, n2, i, flag; printf("Enter two positive integers: "); scanf("%d %d", &n1, &n2); printf("Prime numbers between %d and %d are: ", n1, n2); for (i = n1 + 1; i < n2; ++i) { // flag will be equal to 1 if i is prime flag = checkPrimeNumber(i); if (flag == 1) printf("%d ", i); } return 0; } // user-defined function to check prime number int checkPrimeNumber(int n) { int j, flag = 1; for (j = 2; j <= n / 2; ++j) { if (n % j == 0) { flag = 0; break; } } return flag; } ``` **輸出** ```c Enter two positive integers: 12 30 Prime numbers between 12 and 30 are: 13 17 19 23 29 ``` 如果用戶首先輸入較大的數字，則該程序將無法正常工作。 要解決此問題，您需要先交換數字。