Thread: Why is A$ a valid variable name?

Can someone help me understand why A$ compiles with Visual Studio 2005 as an int variable with no compiler error?

Thanks,
Jeff

Code:

main()
{
   int A$;
   A$ = 17;
}

Well heck Jeff... Why not?




(And BTW... that version of VS is like 4 generations behind the times... VC++ 2010 is the big deal now)

You're maybe thinking of BASIC where A$ would be a string variable. But C has no string data type. Every string in C is a composite of a char variable, with an end of string marker char. This: BOB is just three char's, not a string. BOB'\0' is a string, but you don't see the '\0' char at all.

So a variable with a $ at the end of it's name is not indicative of a string or any certain type of variable, at all.

Thanks for the quick reply Tater.

The site C Programming/Variables - Wikibooks, open books for an open world states the following:

Naming VariablesVariable names in C are made up of letters (upper and lower case) and digits. The underscore character ("_") is also permitted. Names must not begin with a digit. Unlike some languages (such as Perl and some BASIC dialects), C does not use any special prefix characters on variable names.

A Book on C by Al Kelley and Ira Pohl states

A variable name, also called an identifier, consists of a seqence of letters, digits, and underscores, but may not start with a digit.

Nobody seems to talk about '$' being allowed in a C variable name.

I have VS 2010 on another computer but the one with 2005 has a nicer screen

Thanks,
Jeff

Originally Posted by Jeff Hettick

Thanks for the quick reply Tater.

The site C Programming/Variables - Wikibooks, open books for an open world states the following:

Naming VariablesVariable names in C are made up of letters (upper and lower case) and digits. The underscore character ("_") is also permitted. Names must not begin with a digit. Unlike some languages (such as Perl and some BASIC dialects), C does not use any special prefix characters on variable names.

A Book on C by Al Kelley and Ira Pohl states

A variable name, also called an identifier, consists of a seqence of letters, digits, and underscores, but may not start with a digit.

Nobody seems to talk about '$' being allowed in a C variable name.

I have VS 2010 on another computer but the one with 2005 has a nicer screen

Thanks,
Jeff

If nobody told you to breath would you stop?

It works... who cares why it works... and what difference would it make if it didn't?

Excellent question! I'm taking a C Programming class and the instructor asked in a programming exercise. Technically, I just have to asnwer if the variable compiles correctly. It just bugs me that it compiles correctly, and I can assign values to it like any other variable, but the experts don't mention '$' in variable names.

Thanks,
Jeff

Originally Posted by Jeff Hettick

It just bugs me that it compiles correctly, and I can assign values to it like any other variable, but the experts don't mention '$' in variable names.

Thanks,
Jeff

Probably because nobody actually uses it...

The thing is, there's no reason to prevent it... So what's the big deal?

WhiteFlags,

I found section Annex J 5.2 of the C99 specification that states:

"Characters other than the underscore _, letters, and digits, that are not part of the basic
source character set (such as the dollar sign $, or characters in national character sets)
may appear in an identifier (6.4.2)."

This seems to answer the question. Thanks for the help!

Jeff