Read-only memory

ROMRead Only MemoryROMsread-onlyROM chipCCROSEAROMmemoryRead-only memory (ROM)storage
Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices.wikipedia
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ROM cartridge

cartridgecartridgesgame cartridge
Software applications for programmable devices can be distributed as plug-in cartridges containing read-only memory.
A ROM cartridge, usually referred to simply as a cartridge or cart, is a removable memory card containing ROM designed to be connected to a consumer electronics device such as a home computer, video game console or, to a lesser extent, electronic musical instruments.

Mask ROM

mask-programmed ROMFixed ROMmask
Strictly, read-only memory refers to memory that is hard-wired, such as diode matrix or a mask ROM integrated circuit, which cannot be electronically changed after manufacture.
Mask ROM (MROM) is a type of read-only memory (ROM) whose contents are programmed by the integrated circuit manufacturer (rather than by the user).

Firmware

BadUSBflashingflash
Read-only memory is useful for storing software that is rarely changed during the life of the system, sometimes known as firmware.
Firmware is held in non-volatile memory devices such as ROM, EPROM, or flash memory.

Diode matrix

matrixdiode matricesdiode-matrix
Strictly, read-only memory refers to memory that is hard-wired, such as diode matrix or a mask ROM integrated circuit, which cannot be electronically changed after manufacture.
It is one of the most popular techniques for implementing a read-only memory.

Transformer read-only storage

Transformer Read Only Storage
IBM used Capacitor Read Only Storage (CROS) and Transformer Read Only Storage (TROS) to store microcode for the smaller System/360 models, the 360/85 and the initial two models (370/155 and 370/165) of the S/370.
Transformer read-only storage (TROS) was a type of read-only memory (ROM) used in the 1960s and early 1970s before solid-state memory devices were developed.

Control store

Writeable Control Storecontrol storagewritable control store
On some models there was also a Writeable Control Store (WCS) for additional diagnostics and emulation support.
Early types of control store took the form of diode-arrays that were accessed via address decoders, but were later implemented as writable microcode that was stored in a form of read-only memory called a writable control store.

Flash memory

flashNANDFlash ROM
Flash memory, invented by Fujio Masuoka at Toshiba in the early 1980s and commercialized in the late 1980s, is a form of EEPROM that makes very efficient use of chip area and can be erased and reprogrammed thousands of times without damage.
Flash memory is a type of floating-gate memory that was invented at Toshiba in 1980, based on EEPROM (electrically erasable programmable read-only memory) technology.

Programmable read-only memory

PROMPROMsprogrammable ROM
PROM, invented by Wen Tsing Chow in 1956, allowed users to program its contents exactly once by physically altering its structure with the application of high-voltage pulses.
It is one type of ROM (read-only memory).

Non-volatile memory

non-volatilenon-volatile storagenon-volatile memories
Every stored-program computer may use a form of non-volatile storage (that is, storage that retains its data when power is removed) to store the initial program that runs when the computer is powered on or otherwise begins execution (a process known as bootstrapping, often abbreviated to "booting" or "booting up").
Examples of non-volatile memory include flash memory, read-only memory (ROM), ferroelectric RAM, most types of magnetic computer storage devices (e.g. hard disk drives, floppy disks, and magnetic tape), optical discs, and early computer storage methods such as paper tape and punched cards.

Home computer

home computershomehome computing
Most home computers of the 1980s stored a BASIC interpreter or operating system in ROM as other forms of non-volatile storage such as magnetic disk drives were too costly.
Since most systems shipped with the BASIC programming language included on the system ROM, it was easy for users to get started creating their own simple applications.

Android (operating system)

AndroidAndroid operating systemList of Android devices
For example, users modifying or replacing the Android operating system describe files containing a modified or replacement operating system as "custom ROMs" after the type of storage the file used to be written to.
In contrast to desktop Linux distributions, Android device owners are not given root access to the operating system and sensitive partitions such as /system are read-only.

USB flash drive

flash driveUSB flash drivesUSB drive
, NAND has partially achieved this goal by offering throughput comparable to hard disks, higher tolerance of physical shock, extreme miniaturization (in the form of USB flash drives and tiny microSD memory cards, for example), and much lower power consumption.

KERNAL

For example, the Commodore 64 included 64 KB of RAM and 20 KB of ROM contained a BASIC interpreter and the "KERNAL" of its operating system.
KERNAL is Commodore's name for the ROM-resident operating system core in its 8-bit home computers; from the original PET of 1977, followed by the extended but strongly related versions used in its successors: the VIC-20, Commodore 64, Plus/4, C16, and C128.

BASIC

BASIC programming languageGOSUBcompiled BASIC
Most home computers of the 1980s stored a BASIC interpreter or operating system in ROM as other forms of non-volatile storage such as magnetic disk drives were too costly.
These machines almost always had a BASIC installed by default, often in the machine's firmware or sometimes on a ROM cartridge.

Booting

bootloaderboot loaderboot
Every stored-program computer may use a form of non-volatile storage (that is, storage that retains its data when power is removed) to store the initial program that runs when the computer is powered on or otherwise begins execution (a process known as bootstrapping, often abbreviated to "booting" or "booting up"). Later home or office computers such as the IBM PC XT often included magnetic disk drives, and larger amounts of RAM, allowing them to load their operating systems from disk into RAM, with only a minimal hardware initialization core and bootloader remaining in ROM (known as the BIOS in IBM-compatible computers).
The invention of read-only memory (ROM) of various types solved this paradox by allowing computers to be shipped with a start up program that could not be erased.

BIOS

ROM BIOSSystem BIOSBasic Input/Output System
Later home or office computers such as the IBM PC XT often included magnetic disk drives, and larger amounts of RAM, allowing them to load their operating systems from disk into RAM, with only a minimal hardware initialization core and bootloader remaining in ROM (known as the BIOS in IBM-compatible computers).
Originally, BIOS firmware was stored in a ROM chip on the PC motherboard.

Commodore 64

C6464Commodore
For example, the Commodore 64 included 64 KB of RAM and 20 KB of ROM contained a BASIC interpreter and the "KERNAL" of its operating system.
The machine used the same case, same-sized motherboard, and same Commodore BASIC 2.0 in ROM as the VIC-20.

Operating system

operating systemsOScomputer operating system
Most home computers of the 1980s stored a BASIC interpreter or operating system in ROM as other forms of non-volatile storage such as magnetic disk drives were too costly.
The first microcomputers did not have the capacity or need for the elaborate operating systems that had been developed for mainframes and minis; minimalistic operating systems were developed, often loaded from ROM and known as monitors.

CD-ROM

CDCD-ROM driveCD-ROM XA
* Optical storage media, such CD-ROM which is read-only (analogous to masked ROM).
Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory.

Microprocessor

microprocessorsprocessorprocessors
These are in everything from industrial robots to home appliances and consumer electronics (MP3 players, set-top boxes, etc.) all of which are designed for specific functions, but are based on general-purpose microprocessors.
This chip could also arguably lay claim to be one of the first microprocessors or microcontrollers having ROM, RAM and a RISC instruction set on-chip.

ENIAC

Electronic Numerical Integrator And ComputerElectronic computerENIAC (Electronic Numerical Integrator and Computer)
Forms of read-only memory were employed as non-volatile storage for programs in most early stored-program computers, such as ENIAC after 1948.
A number of improvements were made to ENIAC after 1947, including a primitive read-only stored programming mechanism using the function tables as program ROM, after which programming was done by setting the switches.

Computer data storage

main memorystoragememory
Every stored-program computer may use a form of non-volatile storage (that is, storage that retains its data when power is removed) to store the initial program that runs when the computer is powered on or otherwise begins execution (a process known as bootstrapping, often abbreviated to "booting" or "booting up"). Its designers explicitly broke from past practice, stating plainly that "the aim of NAND Flash is to replace hard disks," rather than the traditional use of ROM as a form of non-volatile primary storage.
A non-volatile technology used for this purpose is called ROM, for read-only memory (the terminology may be somewhat confusing as most ROM types are also capable of random access).

Microcode

microprogrammicroprogrammingmicroprogrammed
Engineers normally write the microcode during the design phase of a processor, storing it in a read-only memory (ROM) or programmable logic array (PLA) structure, or in a combination of both.

Bit

bitsbinary digitbinary digits
Consequently, ROM could be implemented at a lower cost-per-bit than RAM for many years.
In certain types of programmable logic arrays and read-only memory, a bit may be represented by the presence or absence of a conducting path at a certain point of a circuit.

IBM Personal Computer XT

IBM PC XTIBM XTXT
Later home or office computers such as the IBM PC XT often included magnetic disk drives, and larger amounts of RAM, allowing them to load their operating systems from disk into RAM, with only a minimal hardware initialization core and bootloader remaining in ROM (known as the BIOS in IBM-compatible computers).
Like the original PC, the XT came with IBM BASIC in its ROM.