I do not understand this code. Why r's decimal, octal, hexadecimal value show garbage value?

Question

This is the code-

  int j;
   printf("Enter the number:");
   scanf("%c",&j);

   printf("You have enter the decimal number %i \n",j);
   printf("You have enter the octal number %o\n",j);
   printf("You have enter the hexadecimal number %x\n",j);
   printf("You have enter the character %c\n",j);

This is my output:

Enter the number:r
You have enter the decimal number 4201074 
You have enter the octal number 20015162
You have enter the hexadecimal number 401a72
You have enter the character r

What does this have to do with JavaScript or Java or Python? — Pointy, May 28 '21 at 15:36

score 1 · Answer 1 · answered May 28 '21 at 15:37

The %c format specifier to scanf expects a char * as a parameter. You're instead passing in an int *.

Using the wrong format specifier triggers undefined behavior which is why you're seeing strange results. What's probably happening behind the scenes is that only the first of the (presumably) 4 bytes of the int variable j are written to, leaving the rest uninitialized and containing whatever garbage was there previously.

Change the type of j to char and you should get the results you expect.

I do not understand this code. Why r's decimal, octal, hexadecimal value show garbage value?

1 Answers1