Master Boot Record (MBR) is loaded into RAM and locates the boot sector. The boot sector then locates the Io.sys.
The Io.sys runs Sysinit and loads Msdos.sys into RAM.
Io.sys then loads System.dat, but does not process at this time.
Io.sys then loads Config.sys and Autoexec.bat. These are not necessary to load the operating system, but are needed when 16 bit (real mode) drivers are used.
Io.sys then loads Win.com which start the operating system.
Win.com loads drivers specified by the registry.
Win.com processes the System.ini and Win.ini files. System.ini is used to configure the memory cache and buffers. Win.ini is used for 16-bit applications. Otherwise, they are run by the registry.
Win.com will start KERNEL32.DLL, KERNEL386.EXE, GDI.EXE, and GDI32.EXE. The Kernel files are the operating systems. The GDI files are responsible for the graphical functions and display.
The Kernel files will load the Explorer user interface, which includes the Desktop, Taskbar, and Start Menu.
The Kernel will then process anything in the Startup folder and restore network connections.
The user can now interact with the operating system.
