It makes me confuse with Legacy BIOS. Is any difference between BIOS and Legacy BIOS?
Thanks

Older style computers which use boot code in the MBR are generally referred to as Legacy/CSM, the CSM meaning compatibility support module which is a component of the UEFI firmware that provides legacy BIOS compatibility by emulating a BIOS environment, allowing legacy operating systems. I have an HP laptop which doesn't have this option and I expect it will eventually disappear on new computers. Even with no Legacy option, my HP refers to it as "BIOS Setup Utility".

The BIOS is a micro code program stored in read only memory. Typically software releases are given numbers. Every once in a while the marketing boys will give the next release a completely new name instead of an incremented number. They do this to make customers think that they are getting a radically new product. So instead of calling a new BIOS release BIOS-2.0 they called it UEFI. If UEFI hadn't been released until the summer of 2023 when Artificial Intelligence became a hot buzz word then the BIOS release name would have included Artificial Intelligence in its name.

Legacy BIOS refers to the BIOS release previous to the BIOS release called UEFI.

BIOS stands for "basic input/output system". The original PC BIOS was the BIOS, now it and UEFI are both examples of a BIOS.

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I have seen online resources which insist that a UEFI is not a BIOS (though it performs a similar task) and that terms like "UEFI BIOS" are oxymorons. On the other hand, the manual for my Lenovo Thinkcentre calls the UEFI the BIOS.

I suspect that a complicating factor is that a lot of non-technical users don't know the difference and think that BIOS just means "startup program". So they'd just be confused if the user manual called it something else.

The BIOS system has been around since 1975 when it was written by Kildall and first used on his CP/M systems and was developed to enable CP/M to be installed on different hardware without being modified. Several years later, IBM began using similar software on its personal computers. A major limitation of the BIOS is being unable to use drives larger than 2TB.

I thought that was a limitation in the partition table format fot MSDOS disks. If you used a GPT disk with a BIOS, wouldn't that get around it?

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Yes.

Both BIOS and UEFI are firmware. Call it that and the problem/confusion goes away ... :shrug:

BIOS is bios, regardless of the type. Linux is still Linux and windows is still windows even though they both have been upgraded over time from 16 bit to 32 bit to 64 bit hardware the name did not change.

Just because legacy bios is no longer used (it had major limitations on the size of drives it supported, and architecture it supported) does not mean the newer UEFI bios (Unified Extensible Firmware Interface) is no longer bios. It is still bios (Basic Input Output System) (also known as the motherboard firmware) that performs the bootstrap functions to start the motherboard and attached devices, and to begin loading the kernel and OS.

Yes, agreed. That has always been my understanding. Terms like BIOS, Legacy and even msdos are often used interchangeably and leads to confusion. Didn't bookmark the site where I read (misread?) that information and can't find it now to know which it was.

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Huh? BIOS = Basic Input/Output System.

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istr that in the very early days of PCs, DOS wasn't supposed to communicate with the disks directly. There would be this low level BIOS code to do it. And then, because BIOS existed, it was the obvious way to start up the machine by reading some kind of startup code from the drive before DOS was loaded.

Was that really so? I know Linux always accessed disks directly, but did DOS?

What we refer to as the BIOS was first created in 1975 and was designed to work on various hardware and was 5 years before DOS existed and was first used with CP/M. IBM used a modified version of it on its computers beginning in 1980/81.

Unfortunately, sometimes old usages take time to go away.

DOS could not talk to the hardware when first powered on. Dos resided on the disk. The hardware had to be initialized by firmware (bios) on the board, including the drive, then dos could be loaded from the disk.