原文： https://www.programiz.com/c-programming/examples/binary-decimal-convert

在此示例中，您将学习通过创建用户定义的函数将二进制数字手动转换为十进制，反之亦然。

要理解此示例，您应该了解以下 C 编程主题：

将二进制转换为十进制的程序

  1. #include <math.h>
  2. #include <stdio.h>
  3. int convert(long long n);
  4. int main() {
  5.     long long n;
  6.     printf("Enter a binary number: ");
  7.     scanf("%lld", &n);
  8.     printf("%lld in binary = %d in decimal", n, convert(n));
  9.     return 0;
  10. }
  12. int convert(long long n) {
  13.     int dec = 0, i = 0, rem;
  14.     while (n != 0) {
  15.         rem = n % 10;
  16.         n /= 10;
  17.         dec += rem * pow(2, i);
  18.         ++i;
  19.     }
  20.     return dec;
  21. }

输出

  1. Enter a binary number: 110110111
  2. 110110111 in binary = 439

将十进制转换为二进制的程序

  1. #include <math.h>
  2. #include <stdio.h>
  3. long long convert(int n);
  4. int main() {
  5.     int n;
  6.     printf("Enter a decimal number: ");
  7.     scanf("%d", &n);
  8.     printf("%d in decimal = %lld in binary", n, convert(n));
  9.     return 0;
  10. }
  12. long long convert(int n) {
  13.     long long bin = 0;
  14.     int rem, i = 1, step = 1;
  15.     while (n != 0) {
  16.         rem = n % 2;
  17.         printf("Step %d: %d/2, Remainder = %d, Quotient = %d\n", step++, n, rem, n / 2);
  18.         n /= 2;
  19.         bin += rem * i;
  20.         i *= 10;
  21.     }
  22.     return bin;
  23. }

输出

  1. Enter a decimal number: 19
  2. Step 1: 19/2, Remainder = 1, Quotient = 9
  3. Step 2: 9/2, Remainder = 1, Quotient = 4
  4. Step 3: 4/2, Remainder = 0, Quotient = 2
  5. Step 4: 2/2, Remainder = 0, Quotient = 1
  6. Step 5: 1/2, Remainder = 1, Quotient = 0
  7. 19 in decimal = 10011 in binary