RANDOM ACCESS MEMORY (RAM) AND READ ONLY MEMORY (ROM)

Ram and Rom are the two types of computer memory that provides storage internal to the computer system. They are the primary storage areas in the computer system. They are part of the computer than holds data and instructions (programs) for processing as well as the intermediate and final results of processing.
Note that the term “memory” is usually used as a short form for physical memory, which refers to the actual chips capable of storing data or information in bits.

Ram: Ram is called temporary because as soon as the microcomputer is turned off, everything in ram is lost. It is also
if them is power failure that disrupts the electric current going to the microcomputer. For that reason, it is a good idea to save your work in every 5 to 10mins (I.e. transfer/save your work to a secondary medium such as hard disk or any secondary storage devices).

Types of ram chips used in pc are: DRAM, SDRAM, SPRAM, and RDRAM. SIMM and dim are two types of memory modules. Ram is measured by the number of bytes it contains. For example 128 kilobytes (kb) of ram contains 128x1028=131,072 bytes because 1kb is equal to 210=1024 bytes. Ram is said to be volatile because whatever is stored in it is lost when computer is turned off.

ROM: Rom is a part of the primary memory where items are stored in an unalterable form. The information placed in it mainly by the regular program instruction and it is lost when the computer is turned off.
Rom devices store information in a permanent fashion and are used to hold programs and data that do not change. Ram devices retain only the information stored in them as long as electrical power is applied to the IC.  Any interruption of power is applied to the contents of the memory to vanish. This refers to as volatile memory.
Rom on the other hand, is nonvolatile. Every system board contains one or two ROM ICS that hold the systems basic input/output system (BIOS) program.
The bios program contains the basic instructions for communications between the microprocessor and the various input and output devices in the system. Until recently, this information was stored permanently inside the Rom chips and could be changed only be replacing the chips.

There Are Different Types of Rom Chips
1. P-ROM; which can only be changed once
2. EP ROM: which can be changed subsequently
3. EEP ROM: it is electrically erasable. The software can be changed and updated.
         Advancement in EEP.ROM technology have produced flash rom devices that allow new bios information be written (downloaded) into the rom to update it. This can be done from an update disk, or download from another computer. Unlike RAM Ics, the contents of the flash Rom remain after the power is removed from the chip. In either case, the upgrade BIOS must be compatible with the system boar it is being used with and should be the latest version available.
   The information in the Bios represents all the intelligent that the computer possesses until it can load more information from another source, such as a hard or floppy disk. Taken together, the Bios software (programming) and hardware. (The Rom chip) are referred to as firmware.