RAM and ROM memories in Micoprosesor

Computer memory devices come in two basic types,RAM and ROM. these words are not as helpful as they could be.RAM standers for 'random access memory, a term which can in fact be applied to both types.ROM is 'read only memory'  which means that the computer system can obtain information stored in the memory('read' it) but can't store anything new in it('write' to it').RAM stores can boat be read from and written to,but both ROM and RAM have the random access facility.Put simply,this means that any data byte stored in the memory chip can be obtained as easily as the next, it doesn't matter whereabouts in the chip it is.

floppy disc systems offer the same facility A program stored anywhere on the disc can (to all intents and purpose) be just quickly accessed as any other.Compare this to information stored on magnetic tape.The first program on the tape is much easier to access than the last -  if you want to do it automatically- so that a tape memory is not regard as being random access.

Rom memory chips are programmed by the manufacture; they contain the computer operating system and standard routines (mini program) that may be used quite frequently;there may be a routine to clear the screen,for example.This information is stored permanently in the ROM chip and is not lost when power to the machine is switched  off. It is termed a 'non-volatile' memory.There is no possibility at all of making future changes to the contents of a ROM chip.The ROM, as with all semiconductor memory devices,is in matrix form and the connections within are permanent.

RAM chips are used for storing the user's program,you can write information the them and read it back again entirely at random according to your programming needs,but all the information's is lost when the computer system is switched off; this is therefore termed a 'volatile' memory system.

 A user would normally 'save' the contents of RAM (usually the program) on floppy or hard disc before turning the power off; such systems are called memory backing store. It is possible to write a program and have is stored  permanently in a ROM chip, but the process is quite complex and requires programmable ROM is used which is programmed during manufacture and would be too expensive to produce in small quantities.