RAM & ROM

Random access memory (RAM):
Random access memory (usually known by its acronym, RAM) is a type of computer data storage. It today takes the form of integrated circuits that allow the stored data to be accessed in any order, i.e. at random. The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.
This contrasts with storage mechanisms such as tapes, magnetic discs and optical discs, which rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than the data transfer, and the retrieval time varies depending on the physical location of the next item.
The word RAM is mostly associated with volatile types of memory, where the information is lost when power is switched off. However, many other types of memory are RAM as well (i.e. Random Access Memory), including most types of ROM and a kind of flash memory called NOR-Flash.

ROM :
It is an abbreviation and name that may refer to:
In Computers and Mathematics:
* Read-only memory, a class of storage media used in computers and other electronic devices. This tells the computer how to load the operating system.
* Mac computers typically included Old World ROM or New World ROM
* ROM image, a computer file which contains a copy of the data from a read-only memory chip.
A ROM image, or simply ROM, is a computer file which contains a copy of the data from a read-only memory chip, often from a video game cartridge, a computer's firmware, or from an arcade game's main board. The term is frequently used in the context of emulation, whereby older games or computer firmware are copied to ROM files on modern computers and can, using a piece of software known as an emulator, be run on the newer computer.
ROM images are also used when developing for embedded computers. Software which is being developed for embedded computers is often written to ROM files for testing on a standard computer before it is written to a ROM chip for use in the embedded system.
* ROM (MUD), a popular MUD codebase
* Random oracle, as in "random oracle model", a mathematical abstraction used in cryptographic proofs
* ROM cartridges, a portable form of read-only memory
* Rough Order of Magnitude (ROM)- Very early cost estimate of a project.