• C

Why doesnt this simple "if" work? problem with char variable

I am learning C, and generally have a pretty good grasp on the basics.  However, the char variables are messing me up.  I dont have a firm grasp on how to use char[] arrays vs char *...

Why wont these if's validate?  The urgency is because I have an assignment due that is failing because of a problem like below
------------------------------------------------------
  float RateA, RateB, amount;
  char *MoneyTo_str, *MoneyFrom_str;

int main() {
  MoneyFrom_str = "DOLLARS";
  MoneyTo_str = "EUROS";

  if ( MoneyFrom_str == "DOLLARS") {
    RateA = 2.00; }
    else
      printf(" error MoneyFrom_str\n");
   
  if ( MoneyTo_str == "EUROS") {
    RateB = 4.00; }
    else
      printf(" error MoneyFrom_str\n");
     
return(0);
}
------------------------------------------------
vettoAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

gripeCommented:
You should use strcmp to compare strings.. Check out the following FAQ page for details:

http://faq.cprogramming.com/cgi-bin/smartfaq.cgi?answer=1057537653&id=1043284385

0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Jaime OlivaresSoftware ArchitectCommented:
>I dont have a firm grasp on how to use char[] arrays vs char *...

Some hints:
You must use char[] to create "buffers" where you want to store some strings (usually with strcpy).
But, if strings previously exist (in another buffer) or is a literal like "DOLLARS", then you don't have to declare an array, just have to point it, a pointer, countersense buffers, don't have a space where to put the string.

This kind of comparison is not valid in C:

if ( MoneyTo_str == "EUROS") {

because MoneyTo_str is a pointer to a string (maybe filled, maybe not), but represents a memory position like 0x12AC568F.
The literal "EUROS" also represents a memory position, if both are pointing to the same memory position, the comparison will be true, but if both point to different memory positions, EVEN if both memory position contains the SAME string, comparison will be false.
0
vettoAuthor Commented:
Points to both, Gripe answered the question the way I love..by giving me the "book" and saying "read this"

jaime explained WHY this wont work (thus points)...I am pretty good at a few interpreted languages where a string value is exactly that, and a var is that value -  not a pointer to an area in memory, so you can see my confusion.  Thanks for the explaination.
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
C

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.