help...Lower and Upper case problem only

i've got a program that will ask for a person initials and only in capital letters...
and if you were to give a lower case then the program will end
here is the program

Code:

#include <stdlib.h>
#include <ctype.h>

int main(int argc, char ** argv)
{
// Mainline Variable Declarations
FILE * output = stdout;
FILE * input = stdin;

char FName;
char toupper;

	//Enter first name
	fprintf(output,"--------------------------\n"); fflush(output);
	fprintf(output,"Enter Your first initial name in capital letters: "); fflush(output);

	//input first name
	fscanf(input,"%c",&FName);fflush(output);

	if(!(FName == toupper))
	{
		fprintf(output,"Error\n",FName);
		//Exit Program if its not M/F/-
		exit(0);
	}

but the problem is if i put lower or upper case it will end program anyway...
please help...thxxx

toupper() is a function that converts its argument to upper case, as you can read here. What you need is isupper().

And since I'm in a good mood, I'll explain how to interpret its prototype:

Code:

int isupper ( int c );

First, let's check the argument: "int c". First, you might think that an integer as argument is a little weird, but if you read some books/tutorials, you'd probably know that a character is stored as an integer value.
As for the return type, it's an integer again. This time, it's a little different and we need to examine first what the return value is: "A value different from zero (i.e., true) if indeed c is an uppercase alphabetic letter. Zero (i.e., false) otherwise."

That's all we need to know, to use it in our code:

Code:

char c = 'a';
if (isupper(c))
{
  puts("Uppercase");
}
else
{
  puts("Lowercase");
}

thank you it works and i learn something more from that...
but i found out other ways..
here it is...

Code:

#include <stdlib.h>
#include <ctype.h>

int main(int argc, char ** argv)
{
// Mainline Variable Declarations
FILE * output = stdout;
FILE * input = stdin;

char FName;

	//Enter first name
	fprintf(output,"--------------------------\n"); fflush(output);
	fprintf(output,"Enter Your first initial name in capital letters: "); fflush(output);

	//input first name
	fscanf(input,"&#37;c",&FName);fflush(output);

	if(!(FName == toupper(FName)))
	{
		fprintf(output,"Error\n",FName);
		//Exit Program if its not upper case
		exit(0);
	}

Of course there are several possible ways, like the one you mentioned. You could also write the following:

Code:

if (c >= 'A' && c <= 'Z')
{
  puts("Uppercase");
}

which would give the same result. But why not use the appropriate function if it exists ?

Oh and btw:

!(A == B) is the same as writing (A != B)

> if (c >= 'A' && c <= 'Z')
Well you could, if you want to make assumptions about your character set being contiguous (read all about EBCDIC).

if ( isupper(ch) ) puts("uppercase");

Originally Posted by Salem

> if (c >= 'A' && c <= 'Z')
Well you could, if you want to make assumptions about your character set being contiguous (read all about EBCDIC).

if ( isupper(ch) ) puts("uppercase");

...

[abbreviation, Extended Binary Coded Decimal Interchange Code] An alleged character set used on IBM dinosaurs. It exists in at least six mutually incompatible versions, all featuring such delights as non-contiguous letter sequences and the absence of several ASCII punctuation characters fairly important for modern computer languages (exactly which characters are absent varies according to which version of EBCDIC you're looking at). IBM adapted EBCDIC from punched card code in the early 1960s and promulgated it as a customer-control tactic (see connector conspiracy), spurning the already established ASCII standard. Today, IBM claims to be an open-systems company, but IBM's own description of the EBCDIC variants and how to convert between them is still internally classified top-secret, burn-before-reading. Hackers blanch at the very name of EBCDIC and consider it a manifestation of purest evil. See also fear and loathing.

...ewwww...

and I already mentioned isupper() in post #2.

Originally Posted by j4k50n

Code:

	if(!(FName == toupper(FName)))
	{
		fprintf(output,"Error\n",FName);
		//Exit Program if its not upper case
		exit(0);
	}

Wrong. Try entering a non-letter and see what it does. FName == toupper(FName) only implies that the character is an uppercase letter if the character is, in fact, a letter. If you pass a non-letter to toupper() it simply returns the character unchanged.

Calling a variable the same name as a function is a bad idea. If it's a local variable, you can't caLL the function. If it's a global one, it may not compile.

Code:

char toupper;

Just so you know.

Originally Posted by brewbuck

Wrong. Try entering a non-letter and see what it does. FName == toupper(FName) only implies that the character is an uppercase letter if the character is, in fact, a letter. If you pass a non-letter to toupper() it simply returns the character unchanged.

yeah i actually wanted it to exit the program if it isn't an upper case letter...
so it works fine with me...thanks for the suggestion though

Originally Posted by j4k50n

yeah i actually wanted it to exit the program if it isn't an upper case letter...
so it works fine with me...thanks for the suggestion though

"It works fine for me" should NEVER decide how you write a program, always try to write as perfect as possible, which in this case comes down to using isupper().