Getting started with C in Mac OS X

Note: as of the time of writing, XCode has been installed on one of the Macs in 213. Hopefully it will be installed on both, soon.

Downloading and installing the compiler

First, check to see if your computer already has XCode installed. Open up the Terminal application, and type

gcc -v

If you see a message like

-bash: gcc: command not found

then you will need to install XCode. There are two ways to install the software:

• If you still have the original Mac OS X install disks that came with your computer, you can use the main install disk and install it from the "Optional Installs" folder.
• Otherwise, you will need to download and install it from the internet by going here and clicking the Mac Dev Center link on the right. You will need to create an Apple Developer ID by supplying a valid email address. The download is very large, so it will take some time.

Once you install the software, typying gcc -v should give you something like this:

Using built-in specs.
Target: i686-apple-darwin10
Configured with: /var/tmp/gcc/gcc-5664~105/src/configure --disable-checking
--enable-werror --prefix=/usr --mandir=/share/man
--enable-languages=c,objc,c++,obj-c++
--program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib
--build=i686-apple-darwin10 --program-prefix=i686-apple-darwin10-
--host=x86_64-apple-darwin10 --target=i686-apple-darwin10
--with-gxx-include-dir=/include/c++/4.2.1
Thread model: posix
gcc version 4.2.1 (Apple Inc. build 5664)

Installing a text editor

You can use the XCode application as a text editor, but I reccomend starting out with something a little smaller. Some of our students have used Aquamacs for Verilog and liked it well enough.

Testing out your installation

Create a folder for your programs in your Documents folder or on your Desktop. Let's use Desktop/ccode/example, for example. Use your text editor to create a file called hello.c containing the following:

#include <stdio.h>

int main(int argc, char** argv) {
  
  printf("Hello, world!\n");
  return 0;

}

Now it's time to compile your program. Open up the Terminal application and type in (substituting whatever path you chose to put the source file in):

cd ~/Desktop/ccode/example
gcc -o hello hello.c
./hello

You should get the output

Hello, world!

If so, you have successfully compiled your first program!

Using make to automate compiles

"Make" is a handy utility that recompiles your programs for you by detecting when the source code is more recent than the executable. We will test it by trying to get it to recompile your hello file, changing the source code, and recompiling again. We'll learn more about how to use make in class soon.

In the same directory as hello.c, use your text editor to create a file called makefile (no .c or .txt extension), containing:

hello: hello.c
	gcc -O3 -Wall -o $@ $^

The space at the start of the second line above is a tab character, not 8 spaces (you can enter a tab by hitting the tab key). Note that make won't work unless you indent certain lines with tabs!

If you go to the MINGW prompt, and type

make

you should see a message like

make: `hello' is up to date.

Now change hello.c to print something else (maybe "Hello, world, again!") and save the file. Go back to the MINGW shell and type

make

once more. It will print the line

gcc -O3 -Wall -o hello hello.c

indicating that it has recompiled your program for you.