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Memory terminology

The amount of work which could be done was restricted by the physical size of memory, Virtual Storage was introduced to relieve this constraint. In Virtual Storage, only currently active 4K chunks of memory known as pages reside in Real Memory.

Paging does occur, in a similar way, on a PC. On the earlier versions of Windows it was possible, via the Control Panel, to adjust the amount of hard drive space reserved for paging activity.

Expanded Storage explained here.

History and Terminology

• Real Storage (Central Memory)
  • When first introduced, there was only Real Memory, sometimes referred to as Central Memory.
  
  
• Auxiliary Storage (Page Data Sets)
  • All inactive pages reside in Auxiliary Storage which is assigned on disk by the use of special page data sets.
  
  
• Expanded Storage
  • No longer supported by 64-bit Operating Systems, memory above the 2GB bar servers the same purpose.