Print ascii magic number upper to lower case

#include <stdio.h>

int main() {
/* ascii letters is a range of
   numbers within a total amount
   of numbers.
   lowercase 97-122 a-z
   uppercase 65-90 A-Z
   to make a lowercase to
   an uppercase -32 to
   the value of the lowercase
   to make uppercase to
   lowercase +32 to
   the value of the uppercase */

char a,b;
 printf("enter a letter,\n"
        "Upper or Lower case\n");

  scanf(" %c",&a);
/* this is assuming an
  actual letter is being
  inputted. */
 if(a >= 65 && a <= 90)
     printf("\nchanged to \n"
     "lowercase %c \n", a+=32);
  else
   printf("wrong input %c\n",a);

 if(a >= 97 && a <= 122)
    printf("\nchanged to\n"
           "uppercase %c\n",a-=32);
  else
   printf("wrong input %c\n",a);


printf("using a switch to "
        "switch it back\n");
    switch(a){
       case 65 ... 90:
          printf("\nchanged to \n"
          "lowercase %c \n", a^=32);
          break;
        case 97 ... 122:
          printf("\nchanged to\n"
          "uppercase %c\n",a^=32);
          break;
         default:
           printf("\nwrong input %c\n",a);
     }


/*

getting the value between the letters
regardless of what they are.

using the above:
Lower case letter (minus) upper case letter.

So it's get the integer values of each
letter. The lower case is the higher
numbers in the ASCII Table so subtract
the upper case value with the lower case
value to get the difference.

Input lower case letter

g = 103

input upper case letter

B = 66

Different is g minus B or
X=103-66

char is an integer so you can easily get
the number of the letter by simply changing
the data type.

char d='h';
int f = (int)d;
printf("%d %c",f,f);

104 h
*/
printf("the difference between 2 "
"letters\nenter an lower case letter\n");
scanf(" %c",&a);
printf("\nenter an upper letter\n");
scanf(" %c",&b);

/*   lowercase 97-122 a-z
     uppercase 65-90 A-Z */

 if (a >= 97 && a <= 122 &&
     b >= 65 && b <= 90)

/*  put everything in one printf */
printf("the ascii integer value "
       "difference between the two"
       " are\n%c - %c\n%d - %d\n"
       "= %d\n",a,b,a,b,(int)a-(int)b);
else
  printf("you failed to follow instructions\n"
         "%c :: %c\n",a,b);
 return 0;
}