Definition: PC memory management

Managing memory in the first PCs in the 1980s was a problem. The PC wound up with confusing memory allocations as its architecture was pushed, patched and expanded to meet the demand for larger applications. The PC's DOS operating system was designed to address no more than one megabyte (1MB) of memory. Today, an entry-level computer has 4,000 times as much.

In the first decade of the PC, technicians had to deal with conventional memory, upper memory, high memory, extended memory and expanded memory (EMS). Countless books were written on PC memory management, and third-party utilities were created to manage memory better (see QEMM and DESQview). There were even classroom courses on the subject. Eventually, memory management in Windows eliminated this headache (see Windows 3.0). See PC operating environments, memory allocation, memory protection, EMS, EMM and DOS memory manager.

 Memory                    Location

 Conventional              First 640K
 UMA (Upper Memory Area)   Next 384K
 HMA (High Memory Area)    Next 64K
 Extended Memory           From 1MB up
 EMS (Expanded Memory      Above 1MB
   bank switched into UMA)

Memory Allocation in a PC
This was the first megabyte of RAM in early PCs.