RAM

R andom A ccess M emory portion of a computer. The term "memory" typically refers to RAM as opposed to hard disc and optical disc storage of files that cannot be randomly accessed without searching by sectors. RAM stores instructions and other files potentially needed for immediate processing of a task at hand. Memory usually can be accessed "randomly" at relatively high speeds. Files stored on computer tape, floppy discs, hard drive, optical drives, etc. are not available in RAM until they are "loaded" into RAM. Four important types of RAM in PCs running DOS are conventional memory, high (upper) memory, expanded memory, and extended memory. When DOS first was designed, 640 Kb of memory seemed like a lot, so out of the then standard 1 Mb of base memory, 640 Kb was designated as conventional memory reserved for DOS and the remaining 360 Mb was high (upper) memory available for other internal system computing functions. Later, memory managers and the Windows HIMEM.SYS file made some of the high memory available for software usage. Another gimmick entailed use of peepholes of size 64 Kb swapping of chunks of memory. However, today the 1 Mb base memory utilized in the most efficient way is not sufficient to run most newer types of software. Memory SIMM chips can be added to raise the RAM to higher levels such as 64 Mb currently popular in multimedia authoring. Upper limits for extended memory options vary with types of PCs. Extended memory is much more important than expanded memory. Often the term extended memory applies to all RAM above the 640 Kb of conventional RAM, although from a technical standpoint it applies to RAM above the 1 Mb base. The term "RAM cache" refers to a section of RAM set aside to serve as a buffer between the central processing unit and auxiliary disc drives. At the present time it is not uncommon to pay in the neighborhood of $200 for each 16Mb of RAM added to computers. (See also Cache , SIMM , VRAM , Hard drive , Flash memory , and CD )