How is the bios for a computer motherboard written how was the first bios written – quora gas house edwards


I can’t answer how the first BIOS was written for a PC motherboard, but I can tell you how the third legal one (there may have been a few others, legal or not, prior to 1984) was done, and by extraction, how they all electricity production in the us were done. ( Actually, the non-legal ones were probably just copied from IBM, with maybe a few small changes so it was not identical, and then reassembled. So I guess that’s not really being “written”)

For IBM, they most likely started by building a list of functions needed. These might be read a keystroke, write a character to the screen, get analog gaming controller input, read/write a sector from a floppy or hard drive, etc. Then they tried to generalize some things with tables (like upper 128 ASCII character font), function entry points, etc. After doing that, they probably just started coding. The assembler used was most likely either a cross-assembler or one of an Intel x86 development system.

For the Compaq and physics c electricity and magnetism formula sheet Phoenix BIOSes, each company needed to have a team analyze the IBM BIOS code and write a complete specification of functions, with specific locations for some of them (Due to bad programmers jumping straight to those locations for their programs rather than extracting those locations from interrupt vectors or pointers). Then a programmer who had never seen the gas tax deduction IBM ROM BIOS code starts writing it, one function at a time (for myself, I started with the simpler functions and worked to the more complicated ones).

Compaq probably used Microsoft’s MASM to write their BIOS. Their functional copying must not have been perfect, as many application programs needed to check for Compaq BIOS, and change their operation slightly for it. Being the 2nd PC-compatible (including the IBM PC) BIOS, application programmers were willing to make an adjustment for it (rather than doing it the right way!).

The IBM BIOS code was not patented, but it was copyrighted. This is the method IBM would try to use to stop people from copying the PC, and in fact sued a number of companies that copied all or portions of the code. A copyright is not what something does, but the specific “artistic” version (in other words the specific code) implementation of that.

Compaq basically had one team that never saw the IBM BIOS test it by considering it a black box. This requires testing the BIOS by giving it all possible inputs electricity distribution map and then seeing what outputs and changes it made. I believe this might only be partially correct, as they needed to know the meaning of the BIOS interrupts (essentially the functions of the BIOS), and probably the basic way to invoke those interrupts.

If Compaq assumed the entire interrupt as a true black box, they would have to create all possible input values for all CPU registers, and then see what changed in the returned values, as well as all of memory and the state of all devices in the PC (Some which may not be readable). This would be a herculean task and probably not doable, so they had to start with some knowledge.

Phoenix, on the other hand, had about 5 or 6 people that went through the IBM PC BIOS code, writing a functional specification of what each did, as well electricity word search answers as table starting points, data structure layouts (e.g. font table), and memory locations affected or referenced. The starting location of each function in the BIOS would be specified, as well as any other know direct references by applications reading locations in the ROM directly (as opposed to using a pointer to the location).

The Phoenix PC BIOS was coded entirely by myself, the PC-XT BIOS had 1 other person (Al Weiner) who did the hard drive code, and the PC-AT BIOS had 1 person gas pain left side (Stan Lyness) that coded the hard drive code and some other small parts. In addition, Phoenix also hired Malcolm Pordes to decode the PC-AT’s 8042 Keyboard controller’s interface (which really was essentially a black box) and to duplicate the code for it.

As my BIOS code ran approximately the same lengths as the orlando electricity providers IBM PC BIOS, I assume that IBM basically had each function and table just assembled as a whole, one after another. The difference in my coding, was there was complete checking for valid function parameters, and any out-of-bounds would be returned as an error, rather than crash. Also, the code was written to be as fast as possible within the constraints of being compatible, and code space was secondary, even though it had to fit in an 8,192 bytes of ROM.

The Phoenix BIOS was written as a third-party BIOS to be sold to many motherboard manufacturers. It was written in MASM and linked with Phoenix’s PLINK-86, an advanced linker, that allowed for code alignment and empty space fill. The code was written in many separate files (generally corresponding to each BIOS function or distinct piece of code, e.g. memory test).

There were many assembler Equates gas tax by state to allow manufacturers to select which compatibility options they wanted. Normally there was a default, but some manufacturers wanted IBM features that made no sense, e.g. weird mapping for Alt-Numpad usage, or having it crash like the IBM BIOS. For simulating a crash, the Phoenix BIOS would go to a tight loop, but interrupts were still active, allowing for a keyboard warm boot (Ctrl-Alt-Del). There were also a few options for slight differences in hardware, as well as options to support chipset configurations.

I wrote it to be tolerant of all the programs that used odd references to the BIOS (much more than Compaq). As a hardware designer as well as programmer, I’d ask many questions to the Phoenix specification team that they never conceived. E.g., are there any non-random values left in a register after a BIOS function that some programmer might be able to use, and any other bizarre usage of a BIOS function I could conceive of (even if it had not yet been used by an existing program electricity worksheets for 4th grade)? Also, I had test programs that ran through various function calls and checked the results, as well as measuring their timing in order to increase speed.

I believe, based upon seeing other BIOSes binary code in debugging motherboards with non-Phoenix BIOSes (before Phoenix acquired some of them) like AMI, Award, and MRBIOS, that these other BIOSes were written by people who were strictly programmers (and not the cleanest code – could be bad programming or from using a C compiler). They had no real understanding of how electricity bill nye worksheet electronics work (based upon their code), and thus were less compatible and less adaptable than the Phoenix BIOS.

After that, some times a mini-OS might be made, at which point more extensive versions can be made. A BIOS is essentially a mini OS without a file system, so a file system doesn’t need to be much more. In fact, the original DOS was just a software wrapper for many of the BIOS functions, with a file system that used the disk hp gas kushaiguda phone number I/O primitives of the BIOS.

And once you have a simple Operating System like MS-DOS running on x86 based computers (not necessarily a PC), you can use native assemblers and compilers to create new code. This was how the original Phoenix BIOSes were written. After that, the code was emulated on the computer that it was assembled on, or a ROM was created and placed in a IBM or clone PC and tested there.