Category : Word Processors
Archive   : TYPING.ZIP
Filename : SYSUNIT3.DAT

<Memory is measured in bytes. A byte can be thought of as one >character or position of data. To make discussing memory size>easier, we usually say "a certain computer has a specific num-=ber of K." One K is equal to 1024 bytes of information. The <Intel 8088 microprocessor gives the IBM PC the capability to >address one megabyte of memory. That is 1024K, which is equal=to 1,048,575 bytes of memory. This discussion describes what >is located in the PC's memory by stating a certain number of K=for each program. Available user memory (what we can use) is =located in low addresses between 0K and 640K. Generally, the <memory above 640K is used by the computer system for various <purposes. While the PC has the ability to address the total >one megabyte of memory, only the amount actually installed can>be accessed. The operating system, DOS, resides in low memory=at all times. It occupies addresses from 0K to approximately >13K. When Disk or Advanced Basic is running, it uses from the>end of DOS, at 13K, to about 25K. Your user programs then oc-;cupy memory space above 25K (if they are Basic programs) or =13K if the are compiled programs. Your user programs may use 8all available user memory if they are designed properly. 9Memory used for CRT screen displays is located in address >space between 640K to 768K. Another 216K of user memory space>is located between 768K and 984K. However, as of this writing=no memory is available for this space. ROM memory is located ;above 984K to the end of memory at 1024K. ROM contains the =Basic language interpreter program and the operating system's ;basic input/output system (BIOS) program. The IBM Personal =Computer Technical Reference manual discusses this in detail.