C Programming Code Examples C > For Loops and While Loops Code Examples C program to convert Octal to Binary number system C program to convert Octal to Binary number system Write a C program to input Octal number from user and convert to Binary number system. How to convert from Octal number system to Binary number system in C. Octal number system Octal number system is a base 8 number system. It uses 8 symbols to represent all its numbers i.e. 01234567 Binary number system Binary number system is a base 2 number system. It uses only two symbols i.e. 0 and 1 to represent all numbers. I have divided the octal to binary conversion in three steps. Extract last digit from octal number. Find binary equivalent of octal digit found above. Combine all converted binary together. Octal to Binary conversion table Decimal Octal Binary 0 0 000 1 1 001 2 2 010 3 3 011 4 4 100 5 5 101 6 6 110 7 7 111 Algorithm to convert octal to binary Algorithm Conversion from Octal to Binary begin: read(octal); OCTALVALUES[] = 0, 1, 10, 11, 100, 101, 110, 111; binary = 0; rem = 0; place = 1; While(octal > 0) begin: rem = octal % 10; binary = (OCTALVALUES[rem] * place) + binary; octal = octal / 10; place = place * 1000; end; write('Binary =' binary); end; #include <stdio.h> int main() { int OCTALVALUES[] = {0, 1, 10, 11, 100, 101, 110, 111}; long long octal, tempOctal, binary, place; int rem; /* Input Octal number from user */ printf("Enter any Octal number: "); scanf("%lld", &octal); tempOctal = octal; binary = 0; place = 1; /* Convert octal to binary */ while(tempOctal > 0) { /* Extract the last digit of octal */ rem = tempOctal % 10; /* * Get the binary equivalent of octal digit * add it to the binary variable */ binary = (OCTALVALUES[rem] * place) + binary; /* Remove the last octal digit */ tempOctal /= 10; /* Increase the place value */ place *= 1000; } printf("Octal number = %lld\n", octal); printf("Binary number = %lld", binary); return 0; }