port, and setup system-default parameters. The MS-DOS essentials are now loaded and control returns to the IO.SYS/WINBOOT.SYS initialization code in memory. Establishing the Environment If a CONFIG.SYS
file is present, it is opened and read by IO.SYS/WINBOOT.SYS. The DEVICE statements are processed first in the order they appear, then INSTALL statements are processed in the order they appear. A SHELL statement is handled next. If
no SHELL statement is present, the COMMAND.COM processor is loaded. When COMMAND. COM is loaded, it overwrites the initialization code leftover from IO.SYS (which is now no longer needed. Under Windows 95, COMMAND.COM
is loaded only if an AUTOEXEC.BAT file is present to process the AUTOEXEC.BAT statements. Finally, all other statements in CONFIG.SYS are processed, and WINBOOT.SYS also looks for the
SYSTEM.DAT registry file. When an
AUTOEXEC.BAT
file is present,
COMMAND.COM (which now has control of the system) will load and execute the batch file. After the batch-file processing is complete, the familiar DOS prompt will appear. If there is no AUTOEXEC.BAT
in the root directory, COMMAND.COM will request the current date and time, then show the DOS For Windows 95 systems, IO.SYS (or
WINBOOT.SYS) combines the functions of IO.SYS and MSDOS.SYS.
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