Is there a good example of how toupper() works?

[michelle international krill lee]

In comp.lang.c, edh at ux.acs.umn.edu (Eric D. Hendrickson) writes:
|
| #include <ctype.h>
| main()
| {
|       char *duh = "Hello";
|       printf("%s\n", duh);
|       while (*duh <= strlen(duh)) {
|               if (islower(*duh)) *duh = toupper(*duh);
|               *duh++;
|       }
|       printf("%s\n", duh);
| }

 The usual suspects have pointed out the obvious problems;  thus 
 the only things remaining are nitpicky in the extreme, but that
 never stopped me from posting before...

1. While not a problem in this context, it's generally advisable
   to use isascii() to check that whatever is being converted to 
   upper case is actually an ascii character.

2. My manual page makes reference to a _toupper() macro.  Adding 
   an "#ifdef _toupper" to check if the macro is available could 
   speed things up marginally, at the expense of defeating what-
   ever locale facility is available.  

3. Making "duh" a register variable wouldn't hurt, especially if
   the above code were to be completely debugged and turned into
   a more general utility.

4. Modification of the constant character array "Hello" may be a 
   no-no for certain compilers and/or certain compiler options.

5. An exit or a return statement would be nice.

6. #includ-ing <stdio.h> is consider good practice in code which 
   uses the standard i/o facilities like printf().