Write a C program to input decimal number from user and convert decimal to octal number system. How to convert from decimal number system to octal number system in C programming. Logic to convert decimal to octal number system in C program.

**Example**

**Input**

Input decimal: 22

**Output**

Octal number: 26

## Required knowledge

### Decimal number system

Decimal number system is a base 10 number system. Decimal number system uses 10 symbols to represent all numbers i.e. 0123456789.

### Octal number system

Octal number system is a base 8 number system. Octal number system uses 8 symbols to represent all numbers i.e. 01234567

## Algorithm to convert decimal to octal

Algorithm Decimal to Octal conversionbegin:read(decimal);octal← 0;place← 1;rem← 0;While(decimal> 0) dobegin:rem←decimal% 8;octal← (rem*place) +octal;place←place* 10;decimal←decimal/ 8;end;print('Octal number'octal);end;

## Program to convert decimal to octal

```
/**
* C program to convert from Decimal to Octal number system
*/
#include <stdio.h>
int main()
{
long long decimal, tempDecimal, octal;
int i, rem, place = 1;
octal = 0;
/* Input decimal number from user */
printf("Enter any decimal number: ");
scanf("%lld", &decimal);
tempDecimal = decimal;
/* Decimal to octal conversion */
while(tempDecimal > 0)
{
rem = tempDecimal % 8;
octal = (rem * place) + octal;
tempDecimal /= 8;
place *= 10;
}
printf("\nDecimal number = %lld\n", decimal);
printf("Octal number = %lld", octal);
return 0;
}
```

Output

Enter any decimal number: 20 Decimal number = 20 Octal number = 24

Happy coding 😉

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