Thread: beginner's question about C

Hi, everyone. This is my first mail to the board. As the subject says, I'm a beginner in C programming. I got a copy of Kernighan-Ritchie's book and I'm starting to learn from it. I have no previous experience in C or Fortran or Pascal. That means you may have to bear with many silly questions from me very often.
I'll go straight to the point. While trying one of the examples on the book (the one about converting temperatures), I decided to try this out: removing the #include <stdio.h> line while keeping the rest of the program intact. I thought that if I did that the program would not compile because the compiler would not find the library stdio.h where the printf function is defined (at least, that's what I understood). But the program got compiled anyway. That surprised me. Does any of you know why this happened?
By the way, if you know of any book/manual/tutorial that might be useful to accompany Kernighan-Ritchie's book in order to learn aspects of C or general programming which are not covered there, I'd be glad to hear about them. I'd also be thankful, of course.

Well, thanks in advance to you all...

Roberto.

Your understanding is correct. Printf is in the #include <stdio.h> area of your program. It should give you an error of an undefined function. Your compiler might have added it on by default or something. Stick with it C is a great language. Oh and welcome to the boards

For gcc 3.2 I tried (where main.c calls printf without including stdio.h)

gcc -ansi -pedantic main.c

and got no warnings/errors.
I needed to add -Wimplicit-function-declaration (or -Wall) before it would show a warning.

Thank you, major blagger. I tried compiling my code with the -Wimplicit-function-declaration option and I got a warning. The compiler performed compilation successfully, though. I had to use the option -Werror-implicit-function-declaration to get an error instead of a warning. This time I did not get any a.out bynary as a result of compilation.
This solution triggered another doubt in me: how does the compiler manage to add the information from stdio.h without the programmer telling it to do that explicitly? I think the answer must lie in the gcc default configuration options, which I have not gone through. I'll try to see if I can figure this out.
Thanks again,

Roberto.

A good set of notes to accompany your K&R2 can be found here

Just be sure you check both sets of notes - one set is more thorough than the other. Have a good look through all of his stuff.