C Programming Code Examples C > Recursion Code Examples Program to Convert a Number Decimal System to Binary System using Recursion Program to Convert a Number Decimal System to Binary System using Recursion The following C program using recursion finds a binary equivalent of a decimal number entered by the user. The user has to enter a decimal which has a base 10 and this program evaluates the binary equivalent of that decimal number with base 2. #include <stdio.h> int convert(int); int main() { int dec, bin; printf("Enter a decimal number: "); scanf("%d", &dec); bin = convert(dec); printf("The binary equivalent of %d is %d.\n", dec, bin); return 0; } int convert(int dec) { if (dec == 0) { return 0; } else { return (dec % 2 + 10 * convert(dec / 2)); } }