IBM PC DOS

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The IBM PC DOS (full name: The IBM Personal Computer Disk Operating System) is an obsolete Disk Operating System (DOS) for the IBM Personal Computer and compatible systems. It was one of the operating systems that dominated the personal computer market between 1985 and 1995. Manufactured and sold by IBM from 1981 to 2000.

Has the same roots as MS-DOS. In fact, MS DOS and PC DOS are two variants of the same operating system with some differences. While PC DOS was originally made for IBM personal computers, MS DOS was aimed at the clone market.

History

5.25 inches Tandon disk drive with a partially inserted dual density diskette containing PC DOS 1.1

The IBM PC

Main article: IBM PC

The IBM task force assembled to develop the IBM PC decided that critical components of the machine, including the operating system, could come from outside vendors. This radical break from the company's tradition of in-house development was the key decision that made the IBM PC an industry standard, but this was done out of necessity to save time. Microsoft was selected for the operating system. IBM wanted Microsoft to retain ownership of any software it developed, and it wanted no part in helping Microsoft except by making suggestions from afar. According to task force member Jack Sams, "The reasons were internal. We had a terrible problem being sued by people claiming that we had stolen their stuff. It could be horribly expensive for us to have our programmers look at code that belonged to someone else, because then they could come back and say that we stole from them and made all this money. We had lost a series of legal disputes on this, so we didn't want to have, worked by the IBM people, a product that was clearly someone else's. We went to Microsoft with the proposition that we wanted this to be their product. IBM first contacted Microsoft to see the company around July 1980. Negotiations continued over the next few months, and the paperwork was officially signed in early November.

Creation of PC DOS

Main article: QDOS

Microsoft purchased a non-exclusive license for 86-DOS (formerly called QDOS) from Seattle Computer Products (SCP) in December 1980 for $25,000. In May 1981, Tim Paterson was hired to port QDOS to the IBM-PC, which used the slower and less expensive Intel 8088 processor, and which had its own specific family of peripherals. IBM watched the progress daily and submitted more than 300 change requests before accepting the product and writing the user manual for it.

In July 1981, a month before the IBM PC was released, Microsoft bought all rights to SCP's 86-DOS for $50,000. This met IBM's main criteria: It looked like CP/M and was easy to adapt existing 8-bit CP/M programs to run under it, notably thanks to the QDOS TRANS command, which allowed the Intel 8080 source code to be translated into language. of machine of the 8086.

Microsoft licensed QDOS to IBM, and it became PC-DOS 1.0. This license also allowed Microsoft to sell DOS to other companies, which it did later when clones appeared calling it MS DOS. The deal was spectacularly successful, and SCP later sued in court that Microsoft had covered up its relationship with IBM to buy the operating system cheaper (even though Microsoft was still under the terms of a nondisclosure agreement and the degree of success of the PC it was not widely anticipated). SCP ultimately received one million dollars as a payment agreement.

Structure

PC DOS consisted of four main components:

The boot sector (boot record), which is located in the first section of the disk or the partition of the disk where the DOS is installed.
The IBMBIO.COM file, which is the interface of the DOS for calls to the IBM BIOS, which was the BIOS of IBM's personal computers.
The IBMDOS.COM file, which is properly the implementation of the DOS, and contains the code of function calls (what we would call the APIs today).
The COMMAND.COM file is the command processor, which receives the instructions (comandos) written by the user and executes them.

Additionally there are a number of executable programs, some configuration files, and others.

PC DOS's brother, MS DOS, had the files IO.SYS and DOS.SYS which were the equivalent respectively of IBMBIO.COM and IBMDOS.COM.

IBMBIO.COM

IBMBIO.COM was the DOS-BIOS filename in many DOS operating systems, and as such, part of PC-DOS, earlier versions of MS-DOS, and DR DOS 5.0 and later (with the exception of DR -DOS 7.06). It serves the same purpose as IO.SYS in MS-DOS, or DRBIOS.SYS in DR DOS 3.31 through 3.41.

The file resided in the boot sector of the disk (the first sector) and was loaded by the boot loader after POST was executed at power on.

In the PC bootup sequence, the first sector of the boot disk is loaded into memory and the code stored there is executed. If this is the DOS boot sector, it loads the first three sectors of the IBMBIO.COM into memory and transfers control to it. The IBMBIO.COM then does the following:

Charge the rest of itself in memory. For this to work, IBMBIO.COM and its entry into the directory should be located in physical positions fixed on the disk and must be stored in the consecutive sectors, conditions that the SYS utility performs.
Load the DOS kernel. The kernel is stored in IBMDOS.COM file.
Starts each default device controller (console, disc, serial port, etc.). At this point, default devices are available.
Call the DOS kernel startup routine.

Under DR-DOS, the first step is skipped, since a DR-DOS boot sector mounts the FAT file system, locates the IBMBIO.COM (or DRBIOS.SYS) file in the root directory, and loads into memory by itself. The IBMBIO.COM file need not reside in a fixed physical location or be stored in consecutive sectors. Instead, it can simply be copied to disk (without the SYS), given a DR-DOS boot sector already resides on the disk.

IBMDOS.COM

IBMDOS.COM was the filename of the PC DOS kernel. The file was located in the root directory on the system disk of the PC-DOS operating system. When Microsoft released MS-DOS, it had an equivalent file called MSDOS.SYS. Later, in the DR-DOS operating system there was also an IBMDOS.COM.

The kernel initialized the operating system and interpreted the contents of the CONFIG.SYS file, which also had to be located in the root directory. A command in CONFIG.SYS specified the location of the command line interpreter, typically COMMAND.COM.

Functions

PC-DOS had a number of functions that could be called by programs via interrupts. There were functions for keyboard input, screen output, console input and output (which was the combination of keyboard and screen treated together), serial port input and output, memory management, file management, file management, directories, disk management, date and time, etc.

Resident and transient commands

The command interpreter for PC-DOS and MS-DOS runs after the executing application terminates (or after a TSR program returns control after installing itself). If, after the application terminates or returns control, the memory-resident shell has been overwritten, PC-DOS will reload it from disk again. The command interpreter is usually stored in a file called COMMAND.COM.

Some commands are internal and built into COMMAND.COM, others are stored on disk in the same way as application programs. When the user types a line of text at the operating system's command prompt, COMMAND.COM will parse the line, and try to find an internally constructed command name. If it doesn't find it, then it looks for an executable program file or batch file on disk with the name of the command. If in any of the two cases it finds it, it executes it and passes the parameters that would be in the line of text written by the user. If it is not found, an error message is printed and the command prompt is refreshed again.

Resident commands varied slightly between different versions of PC-DOS. Typically, the functions DIR (directory list), ERASE or DEL (deletes a file or a directory), COPY (copy files), DATE (displays or adjusts the date), TIME (displays or adjusts the time), CD (changes the working directory), MD (make a directory on the current disk), REN (rename a file or a directory), and a few others, were residents of COMMAND.COM.

Transient commands were either too large to hold in the command processor, or they were used less frequently. Such utility programs would be stored on disk and loaded just like regular application programs, but they were distributed with the operating system. Copies of these utility command programs had to be on an accessible disk, either in the current floppy drive or in the command path set in the command interpreter.

CONFIG.SYS file

Main article: Config.sys

The CONFIG.SYS file is the main PC DOS configuration file. Contains setup and system initialization instructions.

.BAT files

Main article: File batch

Files with the.BAT extension are batch files that contain a set of commands that are processed as if entered on the command line by the user. They are used to automate the execution of a series of commands. Some additional keywords are recognized by the COMMAND.COM shell to make batch files more useful. These additional commands are not useful if typed interactively at the command prompt, but they do allow for flexible processing in a bach file.

Autoexec.bat file

Main article: Autoexec.bat

The Autoexec.bat file is a batch file found in the root directory of the boot disk and is executed at boot time after DOS has been loaded and CONFIG.SYS has been processed.

Versions

PC DOS 1.x

Microsoft first licensed, then purchased 86-DOS from Seattle Computer Products (SCP), which was modified for the IBM PC by Microsoft employee Bob O'Rear with assistance from SCP's Tim Paterson and then employee from Microsoft. O'Rear got 86-DOS running on the prototype IBM PC in February 1981. 86-DOS had to be converted from 8-inch floppy disks to 5.25-inch ones, and integrated with the BIOS that Microsoft was helping IBM write. IBM had more people writing requirements for the computer than Microsoft had writing code. O'Rear often felt overwhelmed by the number of people he had to deal with at the Entry Level Systems facility in Boca Raton. 86-DOS was renamed PC DOS 1.0 for its release with the IBM PC in August 1981. Towards the end of 1981, Paterson went to work on an enhancement, which was called PC DOS 1.1. This allowed data to be written to both sides of a floppy disk, thus doubling the capacity of the IBM machine, and was finalized in March 1982.

PC DOS 2.x

Later, a group of Microsoft programmers (mainly Paul Allen, Mark Zbikowski and Aaron Reynolds) they began work on PC DOS 2.0, the next version for the IBM PC/XT, the first PC to store data on a hard drive. It was a much more sophisticated program than version 1.0, containing 20,000 lines of assembly language code, compared to about 4,000 lines for the first version. It was officially announced in March 1983 or late 1984. Then, in March 1984, the IBM PCjr shipped. It ran PC DOS 2.1, which supported the PCjr's ability to run programs from ROM cartridges and a slightly different disk controller architecture.

PC DOS 3.x

In August 1984, IBM introduced the IBM PC/AT, a computer built around Intel's 80286 processor. It ran on top of PC DOS 3.0, which supported the larger disk drives and higher density (1.2 MB) floppy disks in the new computer. PC DOS 3.1 supported the IBM network adapter card in the IBM PC- Network. PC DOS 3.2 adds support for 3½-inch 720 KiB double-density floppy disk drives, supporting the IBM PC Convertible, the first IBM computer to use 3½-inch floppy disks, released in April 1986.

In June 1985, IBM and Microsoft signed a long-term joint development agreement to share specified DOS code and create a new operating system from scratch, then known as Advanced DOS. On April 2, 1987, OS/2 was announced as the first product produced under the terms of the agreement. At the same time, IBM released its next generation of personal computers, the IBM Personal System/2. PC DOS 3.3, released with the PS/2 line, added support for "1.44 MB& floppy disk drives. #3. 4; (with a capacity of 1440 KiB) of high density of 3½ inches, that IBM introduced in its models of PS/2 based on the 80286 and more advanced. The upgrade from DOS 3.2 to 3.3 was written entirely by IBM, with no development effort on the part of Microsoft, which was working on "Advanced DOS 1.0".

PC DOS 4.x

PC DOS 4.0, shipped in July 1988, was an unsuccessful DOS introduced by IBM testing ideas for their DOS 5, which was in development, and later became OS/2.

Digital Research released DOS 5.0, which caught Microsoft by surprise, but the combination of vaporware, and some rushed coding, allowed Microsoft to avoid the competition. This DOS was also the last DOS for which IBM and Microsoft shared the complete code, and the DOS that was integrated into the Virtual DOS Machine of OS/2 2.0, and later Windows NT. The DOS in these operating systems for the i386 computer never progressed beyond this.^{[citation needed]}

Under the terms of the split, IBM was allowed to stay (and buy the rights) to their own DOS, which they did. They were also allowed to stick with Win-OS/2 (basically Windows 3.10 for OS/2). Microsoft was somewhat specific on which DOS was, since the OEM floppy disks were labeled "MS-DOS and additional tools", ie two products. IBM released its own DOS, with a new editor, and a number of utilities that were older versions?? full versions of PC Tools. The Microsoft tools were Norton tools with limited features.

PC DOS 6.1

PC DOS remained a version of MS DOS until 1993. IBM and Microsoft parted ways - MS DOS 6 was released in March and PC DOS 6.1 (developed separately) followed in June. QBasic was dropped and MS DOS Editor was replaced by E.

PC DOS 6.3

PC DOS 6.3 followed in December. PC DOS 6.30 was also used in OS/2 for the Power PC.

The final split came after DOS 6.30. Note that 6.30 has the improvements that 6.20 had, and that starting with 6.22 and Windows 3.11, the preferred operating system changed from OS/2 to Windows NT.

PC DOS 7.0

PC DOS 7.0 was released in November 1994. The REXX programming language was added, as was support for a new floppy disk format, XDF, which extends the 1.44 MB floppy disk standard. to 1.86MB.

IBM's DOS 7.0, the last release before Boca Raton went out of business, included SAA features (like REXX, IPF view for help, and unpack2 - all coming from OS/2), along with the removal of the incorrect DOS version of most, but not all, utilities.

PC DOS 2000

PC DOS 2000 - released in Austin in 1998 - is basically a slipstream of 7.0 with the 2k year and other fixes applied. For applications, PC DOS 2000 was reported as "IBM PC DOS 7.00, revision 1", in contrast to the original PC DOS 7.0, which was reported as revision 0. IBM continues to use the PC code DOS to compile the DOS boot disks for your servers.

The most recent retail release was PC DOS 2000, which found its niche in the embedded software market and elsewhere. It was based on PC DOS 7.0, and corrected issues with the year 2000 problem. Marketing for PC DOS 2000 included the phrase "includes PC DOS 7.0".

ThinkPad products currently have a copy of the latest version of PC DOS in their rescue and recovery partition.^{[citation required]}

PC DOS 7.1

Since 2003, there is also an OEM version of PC DOS that has LBA/FAT32 enabled, reporting itself to applications as "IBM PC DOS 7.10". Not to be confused with OEM DR-DOS 7.04 and higher, which are also reported as "IBM DOS 7.10" for compatibility purposes.

After Microsoft

PC DOS remained a rebrand of the version of MS-DOS until 1993. IBM and Microsoft parted ways - MS-DOS 6 was released in March, and PC DOS 6.1 (developed separately) followed in June. QBasic was withdrawn and the MS-DOS Editor was replaced with E. PC DOS 6.3 followed in December.

PC DOS 7.0 was released in November 1994. The REXX programming language was added, as well as support for a new floppy disk format, XDF, which extended a standard floppy disk from 1440 KiB to 1860 KiB.