Windows 3.1 featured many changes over its predecessor Windows 3.00a, such as:
Windows 3.1 cannot be run in Real Mode, effectively dropping support for Intel 8086 and 8088 processors; Windows 3.1 requires a minimum of an Intel 80286 CPU.
Virtual Memory, a technique for swapping between RAM and disk space that increases the number of applications that can be run simultaneously.
Data sharing by applications using Dynamic Data Exchange (DDE) and Object Linking and Embedding (OLE)
TrueType Fonts, which are displayed in WYSIWYG fashion and can be scaled to any size. This made Windows 3.1 a viable platform for desktop publishing.
Network-aware File Manager and Print Manager utilities, which enables access to shared network drives and printers. The File Manager itself was significantly improved over the one shipped with Windows 3.0.
While Windows 3.1 could access a theoretical 4 GB of RAM in 386 Enhanced Mode, the practical upper limit for system memory was 256 MB.
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