Memory

It is area with in computer where computer store data in a form of chip. The chip is costly but allows the storage space dynamically. It is composed of a number of locations, each of which a unique address and is capable of storing specified number of bits, such a byte or a word. It is read write memory allowing random access. The storage capacity of main memory varies among computers the memory is classified as.

Primary memory

The CPU access the memory directly without the help of any other device. The primary memory used on a computer is on the motherboard.

Ram (random access memory):-It can read data from the memory and to write new data into memory. Easily and rapidly. These are done through the use of electric signals. Ram requires a constants power supply.

• Static Ram: A Ram that retains stores data as long as power is supplied.
• Dynamic ram: It requires periodic charge refreshing to maintain data storage.

ROM (Read Only Memory):- A types of memory chip that can be read but cannot be written or an altered. A Rom provides permanent storage for program instruction and is used in microprocessors that always execute the same program, such as boat strap leader or a program for on electronic game. A Rom is prepared by manufacture and cannot be altered once for an the chips is made other types of memory are that com only be read are also referred to as ROM since they are used for the same purpose, even though they may be altered through special techniques.

The instruction to start the computer is stored in read only memory i.e., once the information is stored in this memory letter in cannot be changed. It is fixed Rom chip are manufactured with instruction stored permanently on them exam. BIOS (Basic Input Output System).

Prom (programmable read only memory):- A type of Rom that can be programmed to a cuss tamer’s need. The programmed is alone by obtaining a desired bit pattern a process called blasting. A prom can be programmed only, JF an error in the programming is made or change is needed, a new prom must be programmed.

EPROM (Erasable Programmable Read Only Memory):- A type of ROM that be a erased and reprogrammed by the customer. An EPROM it to high intensity ultraviolet light for a period of time usually 15-20 minutes. Once this has been alone all the bits are erased and the EPROM may be reprogrammed. This an EPROM particularly store of a system.

EEROM (Electrically Erasable Programmable Read Only Memory): A type of Rom that can erased and reprogrammed without having to be removed from the circuit board. An EEPROM is reprogrammed electrically and although more expensive is more convent faster method than the one used reprogrammed an EEPROM.

Difference between ROM and RAM:

ROM	RAM
Volatile	NON-volatile
If the power is interrupted the data lost	If the power id interrupted the data is retained
Temporary in nature	Permanent in nature

 

Cache Memory: A high speed memory used as a between the CPU and main memory. It is used to store sequence of instruction from the main memory when the CPU needs an instruction, it first searchers cache memory instead of the slower main memory. It the instruction is found in cache memory. It is called a hit. The ratio of the number of hits to the number of misses can be used to judge the effectiveness of the algorithms controlling the operation of cache memory. Thus cache memory is used to increase the speed of processing by making current program and data available to the CPU at a rapid rate.

Buffer: An area of storage used to temporally hold data being transferred from one device to another. A buffer is used to compensate for the different rates at which hardware devices process data. example a buffer would be used to hold data waiting to print, in order to free the CPU for other tasks since it processes data at a much faster rate.