Windows 3.x

1
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

2
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

3
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.

4
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

5
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 DOSHIGH statement to
  shift portions of DOS from conventional memory
  into the HMA.

6
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.

7
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

8
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

9
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

10
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.