Here is a C program to convert octal number to hexadecimal number system. Octal number system is a base 8 number system using digits 0 and 7 whereas Hexadecimal number system is base 16 number system and using digits from 0 to 9 and A to F. Given an octal number as input from user convert it to hexadecimal number.

For Example:

1652 in Octal is equivalent to 3AA in hexadecimal number system.

### Required Knowledge

## C program to convert a octal number to hexadecimal number

#include <stdio.h> #include <string.h> int main() { int octalDigitToBinary[8] = {0, 1, 10, 11, 100, 101, 110, 111}; int hexDigitToBinary[16] = {0, 1, 10, 11, 100, 101, 110, 111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111}; char hexDigits[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'}; char hexadecimalNumber[30]; long long octalNumber, binaryNumber = 0, position; int digit, fourDigit, i; /* Take an Octal Number as input from user */ printf("Enter an Octal Number\n"); scanf("%ld", &octalNumber); position = 1; /* Finds Binary of the octal number */ while(octalNumber != 0) { digit = octalNumber % 10; binaryNumber = (octalDigitToBinary[digit]*position)+binaryNumber; octalNumber /= 10; position *= 1000; } /* Now convert Binary number to hexadecimal */ position = 0; while(binaryNumber != 0){ fourDigit = binaryNumber%10000; for(i = 0; i < 16; i++){ if(hexDigitToBinary[i] == fourDigit){ hexadecimalNumber[position] = hexDigits[i]; break; } } position++; binaryNumber /= 10000; } hexadecimalNumber[position] = '\0'; strrev(hexadecimalNumber); printf("HexaDecimal Number = %s", hexadecimalNumber); return 0; }Output

Enter an Octal Number 1652 HexaDecimal Number = 3AA

Enter an Octal Number 1234 HexaDecimal Number = 29C

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