ROM: Read-Only Memory

ROM (Read-Only Memory)

ROM (read-only memory) is nonvolatile memory, generally installed by the vendor of the computer during the process of manufacturing the motherboard or secondary components that need to retain code when the machine is turned off. ROM is used extensively to program operation of computers, as well as in devices like cameras, and controls for the fuel injectors in modern cars. However, ROM plays a limited role in the PC. Here, it holds the instructions for performing the POST routine and the BIOS information used to describe the system configuration.

Nonvolatile and Volatile Memory

Nonvolatile and Volatile Memory

There are two major classes of computer memory: Nonvolatile and Volatile. Nonvolatile Memory is retained even if the power is shut off. The setup data held in CMOS, discussed in the preceding lessons, is a good example of nonvolatile memory. If the data is lost when the computer loses power, the memory is said to be Volatile.

Memory

Memory

All computer memory is used to hold binary strings of data destined to be manipulated by the CPU. Think of memory as a vast bank of switches with two positions: on or off. Off is given the value of "0"; on is given the value of "1." This allows the switches to hold binary data based on whether they are open or closed.

Memory Unit (MU)

Memory Unit:-

Memory unit that is also called Main Memory or Random Access Memory is the Primary Unit of the computer. The computer cannot start without Main memory. Main memory is directly accessible by CPU of the computer. The data is stored in main Memory before and after processing. It is a volatile Memory it means it only stores data when computer is turned on.

When we start a computer data from Hard disk is loaded in RAM. The most part of RAM is used by Operating System of the Computer. Remaining Main Memory is distributed between application software.

The Capacity of main memory is measured in Bytes. RAMs are available in GB (Gigabytes).