• C

Inputting a character as a capital letter whether the caps lock is on or off.


When a user inputs a character is there anyway to force it to be upper case ?

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Hi andyw27,

#include <ctype.h>

int toupper(int c);
int tolower(int c);

there are 2 cases
1) you want to check whether user has entered upper case or not
if(((int)c < 65) || ((int)c > 97))

2) you want to force uppercase
int toupper(c)

Don't use c < 65 etc. It's not in the least portable across locales. Better to use isupper. The following is a list of similar functions:

       #include <ctype.h>

       int isalnum(int c);
       int isalpha(int c);
       int isascii(int c);
       int isblank(int c);
       int iscntrl(int c);
       int isdigit(int c);
       int isgraph(int c);
       int islower(int c);
       int isprint(int c);
       int ispunct(int c);
       int isspace(int c);
       int isupper(int c);
       int isxdigit(int c);

       These functions check whether c, which must have the value of an unsigned char or EOF, falls into a certain character class according to the current locale.

              checks for an alphanumeric character; it is equivalent to (isalpha(c) || isdigit(c)).

              checks  for  an  alphabetic  character; in the standard "C" locale, it is equivalent to (isupper(c) || islower(c)).  In some locales, there may be additional characters for which
              isalpha() is true--letters which are neither upper case nor lower case.

              checks whether c is a 7-bit unsigned char value that fits into the ASCII character set.  This function is a BSD extension and is also an SVID extension.

              checks for a blank character; that is, a space or a tab.  This function is a GNU extension.

              checks for a control character.

              checks for a digit (0 through 9).

              checks for any printable character except space.

              checks for a lower-case character.

              checks for any printable character including space.

              checks for any printable character which is not a space or an alphanumeric character.

              checks for white-space characters.  In the "C" and "POSIX" locales, these are: space, form-feed ('\f'), newline ('\n'), carriage return ('\r'), horizontal tab ('\t'), and  verti­
              cal tab ('\v').

              checks for an uppercase letter.

              checks for a hexadecimal digits, i.e. one of 0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F.

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and how is <65 and all that not portable unless you going for not ascii data. In that case, Im not sue if other functions will work too.....

Hi manav_mathur,

é is 130. Which is > 97, but still lower case.

I dont see any character in your post.

I guess 130 coresponds to a accentuated 'e'....which I dont believe to be lowercase,
and on the other hand, what will toupper() do to it??I dont think the result will be what you expect

Hi manav_mathur,

I can see an accented e in my post. Must be a bug in the tool I'm using to post.

toupper will leave a character unchanged if it doesn't understand it, and whether it understands or not depends on the locale that your C library was built with. I don't see why you disagree with me on isupper, when you agree with me on toupper.
Jaime OlivaresSoftware ArchitectCommented:
If you want to restrict uppercase at "input time" then you have to make your own input function.
Something like:

InputFunction(char *buffer, int len)
    char key;
    int i=0;

do {
  key = toupper(getch());   /* <---- Here control is done */
  if (key>32 && i<len) {
      buffer[i++] = key;
  else if (key==8 && i>0) {   /* backspace */
      puts("\b \b");
  else if (key==13) {   /* enter */
      buffer[i] = 0;   /* close string */
    while (kbhit())
} while (true);
I am unable to see the character. I think thats because my browser might not support those chars.

>and whether it understands or not depends on the locale that your C library was built with.
exactly, and you dont know about the poster.

advisory :
#define _toupper(__c)   ((__c) + 'A' - 'a')


Hi manav_mathur,

> exactly, and you dont know about the poster

That's my point. My solution doesn't make presumptions about the poster or his/her local. The toupper function converts a character to an uppercase character if it is a lower case character which has a corresponding uppercase character in the user's locale. Your solution on the other hand, will break on anything other than a-z inclusive i.e. _toupper('A') will return '!' which I do not believe is what the poster wants.

ddunlea's solution is right.  Let's say your character is stored in the variable c.  This would do what you need:

c = toupper( c );

Make sure you #include <ctype.h>.

All this is what ddunlea said first.


P.S. manav and ddunlea - don't want to horn in on anyone's answer...  Just clarifying.  Or maybe throwing my support behind one side of this discussion ;p
Jaime OlivaresSoftware ArchitectCommented:
I agree, in my code will be better to change to:

key = getch();
if (islower(key))
   key = toupper(key);  
> _toupper('A') will return '!' which I do not believe is what the poster wants.

That was an advisory...meaning dont use it. Sorry if it didnt make sense.....ahppens frequently with my posts ;)

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