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C Exercises: Convert decimal number to octal without using an array

C For Loop: Exercise-50 with Solution

Write a program in C to convert a decimal number into octal without using an array.

Pictorial Presentation:

Convert decimal number to octal without using an array

Sample Solution:

C Code:

#include <stdio.h>

void main()
     {
     int n, i, j, ocno=0,dn;

     printf("\n\nConvert Decimal to Octal:\n ");
     printf("-------------------------\n");

     printf("Enter a number to convert : ");
     scanf("%d",&n);

     dn=n;
     i=1;

      for(j=n;j>0;j=j/8)
       {
        ocno=ocno+(j % 8)*i;
        i=i*10;
        n=n/8;
       }
     
     printf("\nThe Octal of %d is %d.\n\n",dn,ocno);
}

Sample Output:

Convert Decimal to Octal:                                                                                     
 -------------------------                                                                                    
Enter a number to convert : 79                                                                                
                                                                                                              
The Octal of 79 is 117. 

Flowchart:

Flowchart : Convert decimal number to octal without using array

C Programming Code Editor:

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Next: Write a program in C to convert a Octal number to a Decimal number without using an array, function and while loop.

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C Programming: Tips of the Day

Printing hexadecimal characters in C:

You are seeing the ffffff because char is signed on your system. In C, vararg functions such as printf will promote all integers smaller than int to int. Since char is an integer (8-bit signed integer in your case), your chars are being promoted to int via sign-extension.

Since c0 and 80 have a leading 1-bit (and are negative as an 8-bit integer), they are being sign-extended while the others in your sample don't.

char    int
c0 -> ffffffc0
80 -> ffffff80
61 -> 00000061
Here's a solution:
char ch = 0xC0;
printf("%x", ch & 0xff);

This will mask out the upper bits and keep only the lower 8 bits that you want.

Ref : https://bit.ly/3vOLizM