CODEWITHSUNDEEP
windowsoperating-systembootstrapping
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Reputation: 35

How does a bootstrap program write itself to ROM?

If I understand OS Bootstrap programs at the very elementary level like I think I do, these programs are typically stored in ROM, read only memory.

If I'm installing a new system, fresh windows 10, how do the win 10/8/7/OS's in general bootstrapper's work?

Does the bios have a basic memory chip/ROM function that is overwritten by the os? How does this work. Thanks!

Upvotes: 1

Views: 1320

Answers (1)

Sam Hobbs
Sam Hobbs

Reputation: 2891

See Read-only memory. People often just say "ROM" but there are many types of ROMs, such as PROMs, EPROMs and EEPROMs. Years ago (I am not sure about now), electronics people did not say "ROM" unless it was truly read-only and could not be modified. Some require special equipment. The type used for BIOSs are usually not modified by the OS.

BIOS is the acronym for Basic Input Output System. Its primary purpose is to provide a basic mechanism for hardware such as the keyboard, monitor and disk drives. The bootstrap portion is a relatively small portion of a BIOS. Modern operating systems do not use the BIOS; DOS did. The bootstrap actually consists of a power-on self-test that does a preliminary test of things like the processor and memory. Then it loads the OS bootstrap from a drive such as floppy, hard drive, DVD or USB.

Since the BIOS and ROM are primarily hardware, it is more appropriate to ask in a hardware group.

As for "how ROM is smart enough to find the HDD's higher-up smarter bootstrap", there are conventions that were established many years ago that bootstraps can use to read the bootstrap. The BIOS bootstrap searches a hard drive for an "active" partition and issues the device command to read from the beginning of it, sector 0 I think. You can look for articles about hard drive partitions.

Upvotes: 3

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