And the actual compiler stuff... -ryan Code: $ system_profiler | egrep "(Model|Processor) Name:" Model Name: MacBook Processor Name: Intel Core 2 Duo $ cat > hello.c << "EOF" > #include <stdio.h> > int main(void) > { > printf("hello.\n"); > return(0); > } > EOF $ gcc-4.2 hello.c -o hello $ file hello hello: Mach-O 64-bit executable x86_64 $ gcc-4.0 hello.c -o hello $ file hello hello: Mach-O executable i386 $ system_profiler | egrep "(Model|Processor) Name:" Model Name: Mac mini Processor Name: Intel Core 2 Duo $ cat > hello.c << "EOF" > #include <stdio.h> > int main(void) > { > printf("hello.\n"); > return(0); > } > EOF $ gcc-4.2 hello.c -o hello $ file hello hello: Mach-O 64-bit executable x86_64 $ gcc-4.0 hello.c -o hello $ file hello hello: Mach-O executable i386