Question about functions is C

Your assumption is correct. Functions you create yourself is just like the functions in the standard library, ie you call printf() and printf does things behind the scenes.

You would include your functions with the #include directive just like the standard functions, so for example: #include "userinput.h", notice the "" instead of < >. The quotes is used when you provide the path to the file, normally this means the header file is in the same directory.

It is possible to have both the definition and declaration in the header file, but, normally the declaration is in the .h file and the implementation is in a corresponding .c file.

 

Cybrscot - I really liked that book, Learn C on the Mac. I started to slow down on Chapter 9 when it started with Data Structures, multi dimensional arrays and linked lists.

I have to say that taking a Pascal programming class at the local city collage has helped a lot. I am now dealing with functions again for my next home work assignment.

This summer I plan on taking the next book in the series after Learn C on the Mac which is, Learn Objective-C on the Mac. He recommends it at the end of your book.

-Lars

 

You have the basic idea. Typically, a larger project will be composed of a whole bunch of .h/.c file pairs, organized so that each one contains a related set of functions. Each function that makes use of another function in another file must #include the .h file that defines (prototypes) that function. This is done to organize the project so that you can focus on small sections of code in a file instead of one huge file with pages and pages of code, and so that you can move important chunks of one project (usually already debugged) to another if it makes sense to.

For example, if you were writing a program to alphabetize user input, you would have your main.h file, which might #include 3 other .h files: one to handle user input, one to handle alphabetizing the input, and one to generate the output. All the heavy lifting code would be in those three files, your main function would be maybe eight or ten lines long. Or the input function could call the alphabetize function, which would call the output function, each one of those .h files including the next .h file, further reducing the code in the main function. Which technique you choose would depend on your needs.

So, you have finished this project and it is time to move on to another one. Suppose you are writing a search tool, and when you look back at the alphabetizer, you see that that input function is so excellent, you can just copy the .h and .c files right over to the new project and use it again, as is, or very nearly (here, the organizational technique can make the job easier or harder).

The file structure of a project can become very large and complex, with many files #including many others. Because the smaller each part is, the easier it is to work on, and the easier it is to modify the way a program operates or looks.

But you were about to learn all this anyway