gcc -nostdlib -o test test.c        # don't use the standard library when compiling (enables using _start() directly)
gcc -m32 -o test test.c             # compile a 32-bit executable
gcc -m64 -o test test.c             # compile a 64-bit executable
gcc -c -o obj1.o obj1.c             # create an object file, but do not link the result(s) into an executable
                                    #       Can be combined with -m{32,64}