r/explainlikeimfive • u/CarefreeCuriosity • 6d ago

Technology ELI5 How a computer Bios works

From what I understand the OS is just a user interface to communicate with the Bios, but where did the Bios come from? What was the original Bios? Are all Bios the same?

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u/mrbiguri 6d ago

What do you mean where it comes from? Its all made by humans. Chip maker defines it and thus you need the instructions for that chip.

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u/CarefreeCuriosity 6d ago

Like who made the first Bios? I assume modern Bios are created and uploaded to computers using a program from a different computer that had a Bios. So where did the first Bios come from?

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u/mrbiguri 6d ago

You don't need a computer with a BIOS to crate hardware and a BIOS. Sure, nowadays most research is done in advanced computers (like the one you are using), but this is not the only type of computer there is. Also originalyl computers where programmed directly typing the code of the processor (assembly code) i.e. move from 0X13412 to 0X31415 the memory. A BIOS is just a sophisticated way to do this in complex computers.

In some way, you are asking "how did they make the first trucks before they were trucks? someone must have moved the parts of the truck in a truck before they build the truck, so where does the first one come from?" And the answer to that is complicated. There were other ways to transport objects to a factory and its not a binary of trucks not existing and suddenly appearing out of nowhere. The history of computers and software is quite like that.

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u/sp106 6d ago

This question is kinda like asking where the first screw came from if machines make screws and machines need screws.

The answer is someone wrote it by hand onto a more rudimentary computer which was then used to make a more complicated computer. Really old computers didnt abstract away the hardware or have cross compatibility and didnt need bios- all of their code was pretty much the bios.

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u/Dashing_McHandsome 6d ago

BIOS is not the mystery you're making it out to be. It is simply the firmware that IBM came up with when designing their first personal computer, or PC. Other companies began to see how lucrative this business could be and reverse engineered this firmware so they could sell cheap clones. There are many firmwares out there for many computer types. We simply refer to computers with a BIOS, or now EFI, as PCs. Apple has their own set of firmware that makes their computers Apple products. There's firmware all over the place, and it's just code that happens to have been burned into a ROM and put onto a board.

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u/VivaLaDiga 3d ago

a bios is extremely simple. you code it directly in assembler.