Not understanding C::B compilation for multiple files

[helasraizam]

Hello,
    I am new to C::B and trying to make my SDL application a project.  I have gone to new project and opened all of the files from there, including the makefile.  The makefile says:

g++ Main.cpp -oGame -Wall -g -lSDLmain -lSDL_image  -lSDL_ttf -lSDL -lSDL_mixer;

My first question is about linking all of those -l's.  I went to project>>build options>>linker settings on my project name ("Tower Defense") and NOT Release.  (I have read the manual but do not understand what release and debug (the latter I disabled outright) are for--though I assume they are for different compiler options?)  I then manually typed in the following into the "Add" prompt:

SDL
SDLmain
SDL_image
SDL_ttf
SDL_mixer

and hoped for the best.  My question: Is this the proper way to link external libraries?  Is the only validator of these names I've typed in a build error?  Is there a pretty list for linkers that I can choose from?  Finally, how can I get the compile code (e.g. the one I wrote in my makefile)?

My second question is about multiple files in C:.  Whenever I tried compiling my cpp and .h files, it always started with Animation.h, and complained because it didn't know what many global variables were--because, of course, they were declared in main.cpp.  Specifically, it said something along the lines of "Error: TERM environment variable not defined", which I think it stopped whining about when I restarted the project.  (BTW I am using Ubuntu and GNU G++).

I fixed the errors about global variables by going to Projects>>Build Options>>Build Targets and disabling everything except Main.cpp in "Build Target Files".  Then, everything worked!  However, this seems highly counterintuitive.  Why should I have to tell it not to compile anything except for Main.cpp?  Shouldn't it read my code and figure it out by itself?  Or am I in the wrong here, and C: does the same thing as G++ and only compile one file--and in this case, why would they all be selected for compiling by default?  Is there an instance in which compiling more than one file would be useful?  (I ask because I figure there must be, or instead of "Build Target Files", it would be "Target File".)

Thanks a lot for your thoughtful answers.

[Radek]

(1) Do not disable the Debug target - unless you are compiling something that really works. The "targets" are different settings of compiler and linker: the "Debug Target" allows you to debug your code (usually all optimalizations disabled, create map file, symbol file, etc.) while the "Release Target" produces optimalized code without debug support. Having more "targets" does not make any harm. Start with "Debug Target" and if everything works, switch to "Release Target", recompile, and check whether everything still works.
(2) Do not type include directories or used libraries in the target options, always select (the button with three dots right of the entryfield). Find the directory (or library) and click "Open". This way, you are sure that the directory (or library) does exist and that the directory name will be entered correctly. In your case, you might be successful but the directories are relative directories, so that they depend on the current directory or on the LIBPATH. They might be found, they need not be found.
(3) The header problem seems to need improving the coding manners. The header should not depend on other files (except the included ones in the header). Perhaps, missing "extern" declarations in the header file?