Functions of ROM
ROM is an acronym for Read-Only Memory. It refers to computer memory chips containing permanent or semi-permanent data. Unlike RAM, ROM is non-volatile; even after you turn off your computer, the contents of ROM will remain.
Almost every computer comes with a small amount of ROM containing the boot firmware. This consists of a few kilobytes of code that tell the computer what to do when it starts up, e.g., running hardware diagnostics and loading the operating system into RAM. On a PC, the boot firmware is called the BIOS.
Originally, ROM was actually read-only. To update the programs in ROM, you had to remove and physically replace your ROM chips. Contemporary versions of ROM allow some limited rewriting, so you can usually upgrade firmware such as the BIOS by using installation software. Rewritable ROM chips include PROMs (programmable read-only memory), EPROMs (erasable read-only memory), EEPROMs (electrically erasable programmable read-only memory), and a common variation of EEPROMs called flash memory.
******ROM (read-only memory) is a computer memory on which data is stored. Once data is stored onto a ROM chip, it can’t be erased and can only be read. It even holds its contents even if the PC is switched off.
ROM is Read Only Memory. In other words, it is memory that cannot be rewritten on the fly. ROM generally comes in the form of IC chips which contain the basic functions to start/run a computer or the devices within it. The most visible form of ROM is the BIOS (think of that screen that shows up when you start your computer. When you start your computer, it accesses the BIOS which tells the CPU how to access the hard drive, video, and basic input devices (IE: keyboard).
How Does a CD/DVD ROM Drive Function?
Data Storage on a CD
Every transition between a bump and a flat surface on the disc translates to binary code of 1’s and 0’s. The data forms a spiral whose path starts from the center of the disc. The CD/DVD ROM drive recognizes this format and can read the data. CDs contain 650 to 700 megabytes of data, and DVDs, which have more storage space due to more layers, can hold nearly 2 gigabytes of data. If there is too much space on the disc without a signal, the drive cannot read the disc, so data is interleaved to prevent too much empty space.
Reading the Data
Interpreting the Data
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