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Major System Files (Part 1)

You are required to identify the names, locations, purposes and contents of major system files. The following tables shows these files for Windows 9x, NT, 200x and XP.

Windows 9x Specific Files

File Location Description
IO.SYS Root A binary executable file that is loaded when the computer is booted. It contains the information required to start your computer. It replaces config.sys and autoexec.bat in later versions of Windows.
MSDOS.SYS Root A text file that contains the start-up and configuration variables and settings. It is loaded by io.sys.
AUTOEXEC.BAT Root This is a batch file containing several commands that will automatically run when the computer starts.
COMMAND.COM Root and Windows This is the command processor for MS-DOS and Windows 9x. It processes the commands that you type at the command prompt. It contains several internal DOS commands to assist in the management of the system which are loaded into memory.
CONFIG.SYS Root This contains commands to tell the operating system how to set up the computer system. It specifies how the main memory will be managed, i.e. it programs the way hardware devices will be controlled and can set limits on system resources.
HIMEM.SYS Root A system file which enables the real-mode memory drivers. It must be present in config.sys for Windows to load. It enables extended memory (using device=himem.sys).
EMM386.EXE Root This is used to emulate expanded memory using extended memory.
WIN.COM Windows An executable file that starts Windows. Type win at the DOS prompt to start Windows.
SYSTEM.INI Windows This stores the information about the PC's system environment, including device drivers, DOS application execution and internal Windows settings.
WIN.INI Windows This contains entries that tell Windows which programs to load and run, and defines the screen, keyboard, mouse, display and fonts.
SYSTEM.DAT Windows One of the two files that make up the registry.
USER.DAT Windows One of the two files that make up the registry.

Next: Major System Files (Part 2)