davidmojo

= = =__Difference between main/internal menory and backing storage/relative benefites of each term of speed and premanence__=

//by david//
All computers have main/internal memory chips to store programs and data while the computer is running. There are two types, ROM and RAM. Accessing data or running software from a memory chip is much faster than from backing storage such as a hard drive.

 **// - //** RAM ( R andom A ccess M emory) chips are described as volatile; the contents are lost when the computer is switched off. When a computer is started up, the operating system (i.e. Windows Vista) is copied into the RAM. Any software that is run ( such as a word processor ) is also loaded into RAM and run from there. When a file is loaded ( such as a word processor document ) that is also loaded into RAM. 
 * RAM advantages you can "write" to ram at any time, and the erase the ram at any time and” rewrite" over it. It has a disadvantage in that you need to constantly supply it with power or it will lose its information. **

  -ROM ( R ead O nly M emory) chips are described as non-volatile; the contents cannot be changed by a program or user and are not lost when the computer is switched off. They are used to store the programs used to start the hardware running //( an example is the BIOS chip which permanently stores the software needed to start a computer's hardware and operating system ).//

** ROM advantage is that (generally) once it is "written" to, it will be there forever. ROMs are often used in fixed situations like the chip that runs a dishwasher, an inexpensive wristwatch, etc. Also, it does not require constant source of electricity **. Both types of memory are referred to as Immediate Access Storage (IAS) because the hardware can access the data so quickly compared to data in backing storage.

 It is always faster to access data from internal memory than from backing storage.  Data stored in internal memory is lost when the computer is turned off but data stored in backing storage is retained.  When programs are run or data files are loaded the contents are copied from the backing storage to the internal memory of the computer.  Internal memory is much smaller than backing storage. It is far too small to hold all the data/programs that would be on the backing storage of a typical computer.