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In computing, BIOS is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process. The BIOS firmware comes pre-installed on an IBM PC or IBM PC compatible's system board and exists in some UEFI-based systems to maintain compatibility with operating systems that do not support UEFI native operation. The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS originally proprietary to the IBM PC has been reverse engineered by some companies looking to create compatible systems. The interface of that original system serves as a de facto standard.
CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/85-based microcomputers by Gary Kildall of Digital Research, Inc. CP/M is a disk operating system and its purpose is to organize files on a magnetic storage medium, and to load and run programs stored on a disk. Initially confined to single-tasking on 8-bit processors and no more than 64 kilobytes of memory, later versions of CP/M added multi-user variations and were migrated to 16-bit processors.
CP/M-86 is a discontinued version of the CP/M operating system that Digital Research (DR) made for the Intel 8086 and Intel 8088. The system commands are the same as in CP/M-80. Executable files used the relocatable .CMD file format. Digital Research also produced a multi-user multitasking operating system compatible with CP/M-86, MP/M-86, which later evolved into Concurrent CP/M-86. When an emulator was added to provide PC DOS compatibility, the system was renamed Concurrent DOS, which later became Multiuser DOS, of which REAL/32 is the latest incarnation. The FlexOS, DOS Plus, and DR DOS families of operating systems started as derivations of Concurrent DOS as well.
86-DOS is a discontinued operating system developed and marketed by Seattle Computer Products (SCP) for its Intel 8086-based computer kit.
x86 assembly language is the name for the family of assembly languages which provide some level of backward compatibility with CPUs back to the Intel 8008 microprocessor, which was launched in April 1972. It is used to produce object code for the x86 class of processors.
The A20, or address line 20, is one of the electrical lines that make up the system bus of an x86-based computer system. The A20 line in particular is used to transmit the 21st bit on the address bus.
In DOS memory management, the high memory area (HMA) is the RAM area consisting of the first 65520 bytes above the one megabyte in an IBM AT or compatible computer.
A fat binary is a computer executable program or library which has been expanded with code native to multiple instruction sets which can consequently be run on multiple processor types. This results in a file larger than a normal one-architecture binary file, thus the name.
A COM file is a type of simple executable file. On the Digital Equipment Corporation (DEC) VAX operating systems of the 1970s, .COM was used as a filename extension for text files containing commands to be issued to the operating system. With the introduction of Digital Research's CP/M, the type of files commonly associated with COM extension changed to that of executable files. This convention was later carried over to DOS. Even when complemented by the more general EXE file format for executables, the compact COM files remained viable and frequently used under DOS.
The Program Segment Prefix (PSP) is a data structure used in DOS systems to store the state of a program. It resembles the Zero Page in the CP/M operating system. The PSP has the following structure:
A File Control Block (FCB) is a file system structure in which the state of an open file is maintained. A FCB is managed by the operating system, but it resides in the memory of the program that uses the file, not in operating system memory. This allows a process to have as many files open at one time as it wants, provided it can spare enough memory for an FCB per file.
The Rainbow 100 is a microcomputer introduced by Digital Equipment Corporation (DEC) in 1982. This desktop unit had a monitor similar to the VT220 and a dual-CPU box with both 4 MHz Zilog Z80 and 4.81 MHz Intel 8088 CPUs. The Rainbow 100 was a triple-use machine: VT100 mode, 8-bit CP/M mode, and CP/M-86 or MS-DOS mode using the 8088. It ultimately failed to in the marketplace which became dominated by the simpler IBM PC and its clones which established the industry standard as compatibility with CP/M became less important than IBM PC compatibility. Writer David Ahl called it a disastrous foray into the personal computer market. The Rainbow was launched along with the similarly packaged DEC Professional and DECmate II which were also not successful. The failure of DEC to gain a significant foothold in the high-volume PC market would be the beginning of the end of the computer hardware industry in New England, as nearly all computer companies located there were focused on minicomputers for large organizations, from DEC to Data General, Wang, Prime, Computervision, Honeywell, and Symbolics Inc.
INT 13h is shorthand for BIOS interrupt call 13hex, the 20th interrupt vector in an x86-based computer system. The BIOS typically sets up a real mode interrupt handler at this vector that provides sector-based hard disk and floppy disk read and write services using cylinder-head-sector (CHS) addressing. Modern PC BIOSes also include INT 13h extension functions, originated by IBM and Microsoft in 1992, that provide those same disk access services using 64-bit LBA addressing; with minor additions, these were quasi-standardized by Phoenix Technologies and others as the EDD BIOS extensions.
A source-to-source translator, source-to-source compiler, transcompiler, or transpiler is a type of translator that takes the source code of a program written in a programming language as its input and produces an equivalent source code in the same or a different programming language. A source-to-source translator converts between programming languages that operate at approximately the same level of abstraction, while a traditional compiler translates from a higher level programming language to a lower level programming language. For example, a source-to-source translator may perform a translation of a program from Python to JavaScript, while a traditional compiler translates from a language like C to assembly or Java to bytecode. An automatic parallelizing compiler will frequently take in a high level language program as an input and then transform the code and annotate it with parallel code annotations or language constructs.
In a general computing sense, overlaying means "the process of transferring a block of program code or other data into main memory, replacing what is already stored". Overlaying is a programming method that allows programs to be larger than the computer's main memory. An embedded system would normally use overlays because of the limitation of physical memory, which is internal memory for a system-on-chip, and the lack of virtual memory facilities.
A volume boot record (VBR) is a type of boot sector introduced by the IBM Personal Computer. It may be found on a partitioned data storage device, such as a hard disk, or an unpartitioned device, such as a floppy disk, and contains machine code for bootstrapping programs stored in other parts of the device. On non-partitioned storage devices, it is the first sector of the device. On partitioned devices, it is the first sector of an individual partition on the device, with the first sector of the entire device being a Master Boot Record (MBR) containing the partition table.
The DOS API is an API which originated with 86-DOS and is used in MS-DOS/PC DOS and other DOS-compatible operating systems. Most calls to the DOS API are invoked using software interrupt 21h. By calling INT 21h with a subfunction number in the AH processor register and other parameters in other registers, various DOS services can be invoked. These include handling keyboard input, video output, disk file access, program execution, memory allocation, and various other activities. In the late 1980s, DOS extenders along with the DOS Protected Mode Interface (DPMI) allow the programs to run in either 16-bit or 32-bit protected mode and still have access to the DOS API.
In computer programming, a self-relocating program is a program that relocates its own address-dependent instructions and data when run, and is therefore capable of being loaded into memory at any address. In many cases, self-relocating code is also a form of self-modifying code.
DOS is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible systems from other manufacturers include DR-DOS (1988), ROM-DOS (1989), PTS-DOS (1993), and FreeDOS (1998). MS-DOS dominated the IBM PC compatible market between 1981 and 1995.
A master boot record (MBR) is a type of boot sector in the first few blocks of partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond. The concept of MBRs was publicly introduced in 1983 with PC DOS 2.0.
References
- 1 2 Taylor, Roger; Lemmons, Phil (June 1982). "Upward migration - Part 1: Translators - Using translation programs to move CP/M-86 programs to CP/M and MS-DOS" [Using translation programs to move CP/M programs to CP/M-86 and MS-DOS](PDF). BYTE . Vol. 7, no. 6. BYTE Publications Inc. pp. 321–322, 324, 326, 328, 330, 332, 334, 336, 338, 340, 342, 344 [342, 344]. ISSN 0360-5280. CODEN BYTEDJ. Archived (PDF) from the original on 2020-01-16. Retrieved 2020-01-15.
[…] Gaining Access to CP/M-86 […] Gaining access to CP/M-86 requires placing the function code in the CL register, placing the byte parameter in the DL register or placing the word parameter in the DX register, placing the data segment in the DS register (the data segment is usually not changed for a converted program), and executing a software interrupt, INT #224. The result is returned in the AL register if it is a byte value; if the result is a word value, it is returned in both the AX and BX registers. Double-word values are returned with the offset in the BX registers and the segment in the ES register. Conversion of programs from CP/M-80 to CP/M-86, then, requires replacing the call to location 5 with the software interrupt INT #224. Another necessary change involves the warm boot. Under CP/M-80, the warm boot may be accessed by a system call with a function code of 0 for a jump to location 0. CP/M-86, however, does not support the jump to location 0. As a result, you must change this program exit in the translated program if the program is to run correctly. Provided that the call to location 5 is replaced with INT #224, that the warm boot change is made, and that the registers are mapped correctly, there should be little problem in getting the translated program to access the CP/M-86 system functions. […] Gaining Access to MS-DOS […] Although MS-DOS has a "preferred" mechanism through a soft-ware interrupt, INT #33, for accessing the system, an additional mechanism is provided for "preexisting" programs that is compatible with CP/M-80 calling conventions, at least for functions in the range of 0-36. As far as system calls within the allowed function range are concerned, the programmer doesn't have to do anything to translated programs to get them to run under MS-DOS other than to correctly map the registers. MS-DOS also supports the warm boot function of CP/M-80. A jump to location 0 under MS-DOS executes a software interrupt, INT #32, which is functionally a program end and the normal way to exit from a program. […]
(13 pages) - ↑ CP/M 2.0 Alteration Guide (PDF). Digital Research. 1979. p. 23.
