In computer science, a readers–writer (single-writer lock, a multi-reader lock,"Practical lock-freedom" by Keir Fraser 2004 a push lock, or an MRSW lock) is a synchronization primitive that solves one of the readers–writers problems. An RW lock allows concurrent access for read-only operations, write operations require exclusive access.

1. <jargon, humour> (WOM) The obvious antonym to "{read-only memory}" (ROM). Out of frustration with the long and seemingly useless chain of approvals required of component specifications, during which no actual checking seemed to occur, an engineer at Signetics once created a specification for a write-only memory and included it with a bunch of other specifications to be approved. This inclusion came to the attention of Signetics management only when regular customers started calling and asking for pricing information. Signetics published a corrected edition of the data book and requested the return of the "erroneous" ones. Later, around 1974, Signetics bought a double-page spread in "Electronics" magazine's April issue and used the spec as an April Fools' Day joke. Instead of the more conventional characteristic curves, the 25120 "fully encoded, 9046 x N, Random Access, write-only-memory" data sheet included diagrams of "bit capacity vs. Temp.", "Iff vs. Vff", "Number of pins remaining vs. number of socket insertions", and "AQL vs. selling price". The 25120 required a 6.3 VAC VFF supply, a +10V VCC, and VDD of 0V, +/- 2%. 2. bit bucket. [Jargon File] (2007-03-24)

Read–write memory is a type of computer memory that can be easily written to as well as read from using electrical signalling normally associated with running a software, and without any other physical processes. The related storage type RAM means something different; it refers to memory that can access any memory location in a constant amount of time.