What system and computer should a programmer use?

Mostly good answer so far. The Vista advice is off-base in my experience. There are very few computers that can run Vista that don't also run 7.

You do need an Apple computer to (legally) develop for any Apple device (iPhone, iPad, iMac, iDontCare) since Xcode is only available on OSX and OSX is only licensed for use on genuine Apple hardware (iMac, Mac Pro, and notebooks). There are, however, bootleg installation procedures to get some OSX versions running on PC hardware. Google for "hackintosh" if that interests you.

For Windows or for Linux/FreeBSD/etc., most any PC with enough memory is enough. I like to have 2GB per core, but until you start developing high-res graphics (incl. games) or very large scale business/web apps, that's probably overkill. For your first year of programming, 4GB is probably enough on a Win7 or Win8.1 system.

The OS version matters. You can't get the full use of 4GB or more with a 32-bit Windows OS. Get a 64-bit version. Also, there are limitations on the home versions of Windows that might be a problem when you start testing networking code. Get a standard (formerly "professional") or "ultimate" edition.

If you want to develop Windows mobile apps, you must have Windows 8 (or 10 if you're brave enough to run it). I find 8.0 as useless as Vista, but 8.1 is usable. Supposedly 10 is going to remember that most installations of Windows don't have touch screens.

It depends on what language you have to use. Generally, most languages are available on all platforms. But if you need something like say, Objective C or Swift, you'd need a Mac. But anything else, it's usually fine with any computer running Windows, Linux and etc.

You don't really need a good computer to make programs on. But if you're working on some high end stuff like intensive games as EddieJ has said, then you'll definitely need a more powerful computer.

If you work for Bussiness i recommend you Windows Vista.

If you work for Programming Windows 7 is best.

Well for computer you need about 4 GB RAM.

Graphic Card: AMD Radeon HD Series 6200+

Processor: 2.8 gHZ+

Sorry for bad english im from Serbia.

A decent cpu and an SSD is about all that is really needed. We keep our computers around 16GB of RAM too. A second display is really nice to have as well. You don't need super high end at all.

Most current systems are perfectly adequate unless you are writing programs (such as complex games) that require a more powerful computer.

I must express my thanks and appreciation to the online product key vendor frevvy. The guys of the technical department answer my questions and provide the instructions so professional and patient.