If you own an Android device, or for that matter visit any Android-related news site then you will have heard about ROMs. Though a lot of people catch onto what ROMs are, for some people it’s not such an easy thing to get your head around. If you aren’t quite sure what a ROM is, hopefully I will clear things up for you today.

First I should explain what a ROM is. The term ROM is misused, and a pseudonym. Up until recently, ROM’s were storage chips consisting of Read-Only-Memory. Ever played Gameboy games? They were ROM’s. Sometimes there was a separate area in the cartridge where you would save games to, but the game itself was Read-Only. You couldn’t modify it. The term which is closer to being correct with reference to Android, is Firmware. You can easily replace it all, if you choose to.

This board has a few ROM chips, one of which tells the device how to boot the Android software (Firmware)

When people talk about installing ROM’s on their devices, they are referring to erasing/overwriting old Android software/system files, and replacing them with new ones to alter the behaviour of Android and the device. If you’ve ever reinstalled your computers operating system (Windows 7, OSX, Linux), this is pretty much the same procedure. Wipe the disk or ‘memory’, then give the computer some new software for it to boot into.

Custom ROMs
JBThemes

Carbon Glass Theme for ICS

A custom ROM is one that has undergone any modification from being a pure distribution of Android. Google make the Android source code available for anyone to play around with, and people take this code and alter it for themselves. Whether to add features they come up with, or to redistribute it with fun tweaks and additions. So a custom ROM can range in definition from some custom code modifications to make Android run better on a device, all the way to changing the homescreen, background services, and default software.

Many software experts collaborate together in communities to build the fastest or most feature filled ROM’s. The most popular today are CyanogenMod (which supports over 70 devices!), AOKP (a lightweight ROM with plenty of customisation options), and Android Revolution, a heavyweight ROM which often focusses on looking great. Just because these Android builds are made by ‘ordinary people’ and not highly paid developers at HTC or Samsung doesn’t mean they are full of bugs or risky to use. In most cases the software built by communities is ten times better. Release cycles are much shorter, fun features can be put in, and anyone can contribute an idea to the development.

I like to use AOKP myself, and in the screenshot below is an example of how much they let you customise things. My Navbar, Clock, and battery-charge-level bar are neon-green. Also note that my WiFI Signal is measured by percentage, and as well as the charge meter running along the top of the nav-bar, I have a circular meter in the bottom right […]