I need to know three ways to change a character letter, if it is lowercase,
   to an uppercase letter.

Do your own homework.  You'll learn more that way.
--
"In My Egotistical Opinion, most people's C programs should be indented six
 feet downward and covered with dirt." -- Blair P. Houghton
Please: do not email me copies of your posts to comp.lang.c
        do not ask me C questions via email; post them instead

Given that you have these two lines:

#include <ctype.h>

and

char ch = 'a';

in appropriate places in your code, you can choose any one of these
techniques:

1) ch = (char)toupper((int)ch);
2) ch = (char)toupper((int)ch);
3) ch = (char)toupper((int)ch);

IIRC there is no other technique that is guaranteed to be portable across
different character sets. Therefore, EITHER I'm wrong and I missed a
couple, OR your lecturer, a guy who ought to know better, is convinced
and/or is trying to convince you that C is only implemented on ASCII-based
platforms.

--
Richard Heathfield

The bug stops here.

Method 1:
    Use ANSI-C function "toupper":

    for( i = 0; str[i] != '\0'; i++ )
        str[i] = toupper( str[i] );

Method 2:
    Check the decimal value of the characters.  If it's between 97 and 122,
substract 32:

    for( i = 0; str[i] != '\0'; i++ )
    {
        if( 122 >= str[i] >= 96 )
            str[i] -= 32;
    }

Method 3:
    Build a table containing the upper case equivalence of each lower case
characters:

    static charTable[2][27] = { "abcdefghijklmnopqrstuvwxyz",

"ABCDEFGHIJKLMNOPQRSTUVWXYZ" };

    for( int i = 0; str[i] != '\0'; i++ )
    {
        for( int j = 0; charTable[j] != '\0'; j++ )

            if( str[i] == charTable[0][j] )
            {
                str[i] = charTable[1][j];
                break;
            }
        }
    }

Hope this will help.

Nicolas Thomassin
CGI Consulting inc.

2. Use a data structure like struct {char lc, char uc} in a 26-element
array. Load each lowercase and its corresponding uppercase character
into the data structure, and create a search function.

3. Put all 26 letters into a relational database table. Use the uppercase
facility provided by the database to do the conversion when you select
the character.

Scott

Two out of three ain't bad - but never forget that EBCDIC will bite you if
you turn your back on it.

--
Richard Heathfield

The bug stops here.

char a[][27] = {"abcdefghijklmnopqrstuvwxyz", "ABCDEFGblahblah

and some code for looping through a[0] looking for a match, then using
a[1][i], which seemed a workable method to me.

Check the thread history or DejaNews for his exact code.

--
Richard Heathfield

The bug stops here.

--

Here's a trick I just read about (ch is some lowercase letter):

ch = (ch - 'a') + 'A';

Note 1:  It would seem this assumes an ASCII character set, which from
reading the thread sounds like a big no-no :-/

Note 2:  Why anyone would do this when toupper() is available is beyond me
(reinventing the wheel?)

Of course my perspective is still pretty limited...

Chris

No doubt my attitude would be different if I had to write apps for an
international user-base.

As it happens, I would use toupper( ) anyway, so I hope I can escape from
this with a little light grilling rather than a major flame.

/me crosses fingers, dons fireproof underwear and Dann-proof helmet, and
runs for cover. :-)

--
Richard Heathfield

The bug stops here.