Computer and Software
Your computer can be nearly anything, some people use regular desktop computers, some use laptops, and some have even written programs for micro controllers (such as the Arduino) that run G-Code, Basically you need something that can convert the G-Code into "steps" to send to the motor controller.
Most people will end up using an older computer that no longer functions as a decent desktop, just about any old "hand-me-down" will do. After that you need some software that will convert and drive the machine.
There are a few options:
- Mach3 - probably the most popular because it is fairly cheap and fully featured
- EMC2 - Open source and runs on Linux - this one is also very popular because it's free