newbie problem

Hello,

I am just starting out in learning C and I want to make a simple program that creates a string, from the options a user inputs and then sorts that string into a correct format for display.
I have put a comment at where the program is going wrong, can anyone tell me where I am going wrong?

Also I was wondering, I want to put this into a gui, would I be best coding the gui into it at the same time, or is it just as easy to get it working correctly in command prompt, then
putting the gui in around it?

Code:

if (num == 2) { strcat(string, define1); printf(" \n\n a - define2\n b - define3\n c - define4\n d - define5s\n e - define6\n f - define7\n"); b = getchar(); } if (b == 'a') { strcat(string, define2); } else if (b == 'b') { strcat(string, define3); } else if (b == 'c') { strcat(string, define4); } else if (b == 'd') { strcat(string, define5); } else if (b == 'e') { strcat(string, define6); } else if (b == 'f') { strcat(string, define7); } if (b == 'e' || b == 'f') { printf(" \n\n a - define12\n b - define13\n c - define14\n d - define15\n"); c = getchar(); // works good up to here, it prints above statement, but then ends rather than asking for the next option. } if (c == 'a') { strcat(string, define12); } else if (c == 'b') { strcat(string, define13); } else if (c == 'c') { strcat(string, define14); } else if (c == 'd') { strcat(string, define15); }

Thanks

Quote:

Originally Posted by redsfan

can anyone tell me where I am going wrong?

Yep. This is the number one most common problem for newbies at cboard which is why I wrote this:

STDIN pitfalls

Basically, this happens because you need to push return, which "\n" is also a character and it gets left in the stdin buffer. Try this:

Code:

#include <stdio.h> int main(int argc, char *argv[]) { int x = getchar(), y = getchar(); printf("ASCII: %d %d\n",x, y); return 0; }

The second one will always be ascii 10, the newline. (read that page!)

Quote:

Also I was wondering, I want to put this into a gui, would I be best coding the gui into it at the same time, or is it just as easy to get it working correctly in command prompt, then
putting the gui in around it?

What library are you going to use for the GUI? I'm presuming you are not sure and have not done any GUI programming yet. I'm also going to recommend you forget about it for a while. GUI stuff is much more complicated that you think it is going to be. You need to develop some basic C skills first.

Thanks mk27 that explains it and it was fixed by putting in fflush(stdin); :)

Could you tell me what you are doing in this following line?

Code:

int main(int argc, char *argv[])

It looks like your creating an integer variable argc and a character variable *argv but why put these inside the main() function? and what is the purpose of the astrix?

Quote:

What library are you going to use for the GUI? I'm presuming you are not sure and have not done any GUI programming yet. I'm also going to recommend you forget about it for a while. GUI stuff is much more complicated that you think it is going to be. You need to develop some basic C skills first.

Well I use MinGW and I have seen glade mentioned as a good gui builder, but I don't really have any idea and have never done any gui programming, I will leave it alone for now though, I no I have much to learn yet.

Quote:

Originally Posted by redsfan

that explains it and it was fixed by putting in fflush(stdin);

Unfortunately, that is not a correct fix as fflush() is undefined for input streams like stdin. Rather, you should do something like use getchar() to discard what remains on the input stream.

Quote:

Originally Posted by redsfan

Could you tell me what you are doing in this following line?

Read the tutorial on command line arguments.

Quote:

Originally Posted by laserlight

Unfortunately, that is not a correct fix as fflush() is undefined for input streams like stdin. Rather, you should do something like use getchar() to discard what remains on the input stream.

Ahh I see, that works fine, thanks.

Quote:

Originally Posted by redsfan

Ahh I see, that works fine, thanks.

Of course, redfan could also have read the page, where I explain why not to use fflush(stdin) and provide some alternatives...:( Which IMO another getchar() is the simplest, but not the best, and you should understand the why of this.

ps. the command line arguments just got left into that example because I tend to always use the same "template file" when testing and evidently last time that involved command line args. Normally "int main()" or "int main (void)" are fine.

Quote:

Originally Posted by MK27

Of course, redfan could also have read the page, where I explain why not to use fflush(stdin) and provide some alternatives...

Sorry I didn't know there was a link in there, I was wondering what page you were reffering too:rolleyes: So I went of looking when you told me what the problem was and fflush(stdin)
was the first alternative I came across. I will read through the page you provided, thanks.