Download Brad`s lecture on Windows 3.x

Windows 3.x
Umbrella term for Windows 3.0, 3.1,
Windows for Workgroups, etc.
 Win 3.x is just an operating environment
that runs on top of DOS (unlike 95,
which is also an operating system)
 Like DOS, Windows 3.x filenames are
limited to 8 + 3 characters
 Icons are arranged in group files (.GRP)

– each group file represents contents of one
window
Windows 3.x core files

KRNL386.EXE
– controls how programs use memory and IO
– loads and executes Windows applications

USER.EXE - user interface
– creates and controls onscreen windows
(moving, resizing, deleting windows)
– I/O through mouse, keyboard, COM ports

GDI.EXE- Windows GUI
– graphics on screen
Windows 3.x INI files

.INI files are used to initialize Windows
– plain text files, can be edited in text editor

SYSTEM.INI
– identifies device drivers
– only INI file that actually needs to be
present in order to load Windows 3.x
– key sections of the SYSTEM.INI file are the
[Boot], [Keyboard], [Drivers], and [386enh]
sections.
Windows 3.x INI files

WIN.INI controls desktop appearance and
file associations
PROGMAN.INI defines desktop windows
 Others: (less important)

– CONTROL.INI- set colors and background
patterns
– MOUSE.INI- mouse hardware settings
– PROTOCOL.INI- networking on Windows
for Workgroups
HIMEM.SYS
HIMEM.SYS is the device driver for
accessing memory above 640K
(expanded and extended memory)
 HIMEM.SYS also creates High Memory
Area (HMA): a 64KB area of memory
above the 1MB address space
 With HIMEM.SYS, can use DOS=HIGH
statement to shift portions of DOS from
conventional memory into the HMA.

HIMEM.SYS cont.
For Windows 3.x to run, HIMEM.SYS
must be loaded in CONFIG.SYS
 HIMEM.SYS should be listed in the
CONFIG.SYS file before any other
memory managers or device drivers.

Windows 3.x modes

real mode- 8086 mode- now obsolete
– runs in DOS limit of 1 MB RAM

standard mode - 286 protected mode
– could address up to 16 MB memory
– can only run 1 DOS program at a time

386 enhanced - 386 protected mode
– can address up to 4 GB RAM
– supports virtual memory
– can run multiple DOS programs at same time
Win 3.x and virtual memory
Windows 3.x in 386 protected mode
supports virtual memory (unlike DOS)
 Virtual memory: allows CPU to use part
of hard drive to simulate extra memory swap file: the part of the hard drive that
thinks its RAM- (see Meyers 576-580)

– functions as a temporary storage area
– kicks in only when you run out of RAM
– swapping in and out slows system down
Windows 3.x swap files
Two types of swap files:
 Temporary virtual swap file

– WIN386.SWP
– only exists when Windows is running,
erased when exit Windows

permanent swap file
– 386SPART.PAR
– never erased
Win3.x: Cooperative multitasking

Win 3.x uses cooperative multitasking
– OS transfers control to the various
applications, which “cooperate” with each
other to share control of the system.
– 1. OS gives control to the running
application
– 2. When the application completes its task,
it gives control back to the OS
– 3. OS then gives control to the next
scheduled application.