Read-only memory

See also: Read-only memory (homonymy)

A read-only memory ( ROMANIAN or Read-Only Memory in English, marked /r ɛd/) is a volatile memory not , i.e. a memory which is not erased when the apparatus which contains it is supplied more with electricity.

The English term ROMANIAN carries to confusion because it indicates at the same time

  • all the types of memories not-birds
  • and one of these types, the type of memory which can be neither programmed nor unobtrusive by the user.

Use

The dead memories are used, inter alia, to store:

  • necessary informations with the starting of a Computer (BIOS, instructions of starting, Microcodes); since the dead memories cannot be modified, there is no risk of accidental obliteration by the user; in the case of the memory of a BIOS which it is possible to modify, it is wrongly that certain indicate it under the name of ROMANIAN memory. There exists for these memories a name suitable and used by manufacturers like IBM and Intel. This name is NVRAM ( not-bird RAM );

  • of the tables of constants or the tables of conversion factors;

  • of the video games of old generations; because of its low storage capacity, the read-only memory was replaced by CD-ROM and DVD for the storage of the video games;

  • within the framework of the use of emulator S; one uses a copy ( image ) of the read-only memory of the emulated platform, but it is generally on CD or diskette and not on a physical read-only memory.

The access times to the read-only memory are of about size of 150 Nanoseconde S compared to an access time of approximately 10 nanoseconds for the Random access memory. To accelerate the data processing, the data stored in the read-only memory are generally copied in a random access memory before being treated. One calls this operation the shadowing .

Types of read-only memory

The dead memories are classified according to the possibility of programming them and of erasing them:

  • the ROMANIAN ( R ead O nly M emory) whose contents are defined during manufacture.

  • the PROM ( P rogrammable R ead O nly M emory) are programmable by the user, but only once.
  • the EPROM ( E rasable P rogrammable R ead O nly M emory) are erasable and programmable by the user. Like deleting is done while placing the memory in a special machine, the memory must be easily ôtable of its support. These memories are also called UVPROM ( U will ltra V iolet P rogrammable R ead O nly M emory) because they are erased by bombardment of ultra-violet.
  • the EEPROM ( E lectrically E rasable P rogrammable R ead O nly M emory) are erasable and programmable by the user. They are easier to erase than EPROM because they are erasable electrically thus without physical handling.

See too

Related articles

Simple: Read-only memory

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