TLAs from RAA through RZZ

RAM

Random Access Memory
Computer memory that you can write to and read from in a random order (no sequence constraints). See also ROM and WOM.

RGB

Red Green Blue
A color representation where the color is split in a sum of primary color components red, green and blue. Other representations are CMY, YIQ, HSV and HLS. See also CIE and ACE.

ROM

Read Only Memory
A part of memory for your computer where the processor can only read from. Normally, this is a special type of chip. The counterpart of rom is WOM and RAM.

ROS

Rom Operating System
This is a computer's operating system loaded and executed from ROM (instead of being loaded from floppy/harddisk) and controls the computer's behaviour. The kind of computer that operates on a ros does not have any disc-drives. Some of us might still remember the relics of Apple II, C64 and ZX Spectrum (and also some other oldies). All of these machines operated without a disc-drive (at least at first). Because they did not have a disc-drive, they didn't need a DOS.

RPC

Remote Procedure Calling
A mechanism to call program functions of and on another machine within a network (mostly a server of a LAN or WAN).

RTF

Rich Text Format
A format for text files with encapsulated formatting or typesetting information. It looks a bit like TEX formatting. Only tex is much more flexible.

RTM

Read The Manual
Commonly heard response to questions from stupid users or from computer people who think they know it all. If this answer doesn't seem to help, you are likely to get the response RTFM (Read The Fu*#! Manual). If that also doesn't work or those who should be able to answer the question also don't know, then the answer would be RTFMA (ReadThe Fu*#! Manual Again). In general, non of these abbrevs have any influence on the behaviour of computer people since they still think that they know it all and hate reading manuals.