What do candy stripes across my iMac screen mean the system will not load is the software or hardware issue? How do I proceed please?

Yes, the computer is obsolete meaning parts are no longer available. Considering the computer is from 2012 that also means it will not run current versions of Mac OS. If you want to take it to an independent Apple Authorized Service Provider you can find one by using Apple Authorized Service Provider Locator (AASP) & Genius Appointment or you can call AppleCare and they can help you find one in your general area.

However because parts availability will be a problem after it has been professionally diagnosed, I would strongly recommend just cutting bait and buying a new Mac. You have lots and lots of options available to you so take your time. When I say you have lots of options, you can get another iMac (Apple just released new 24" models October 30th), Mac minis, MacBook Airs, MacBook Pros, Mac Studio etc. You can also buy a refurbished Mac (www.apple.com at the bottom of the home page) which are a great option.

Finally, if cash is a problem remember Apple offers 12 month same as cash if you have an AppleCard.

Difficult to tell however this sounds like a failed GPU which would be hardware. I would strongly recommend that you call AppleCare, if you don't know the phone number in your area please click AppleCare Contact Info to find it.

What is the model year of the device? If you don't know, click the Apple symbol in the upper left of the display and then click About this Mac and it will tell you the model year.

Sadly, It seems like your GPU has failed. I suggest either servicing the computer (which might not be worth while) or getting an M3 iMac or equivalent device.

Sounds like a hardware issue. How old is the iMac?