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              	             http://blacksun.box.sk

                           _____________________________

    ______________________I          Topic:             I_____________________

   \                      I                             I                    /

    \     HTML by:        I    The History of DOS       I   Written by:     /

    >                     I(c)1999 by Paroxysm(20-11-98)I                  < 

   /      Martin L.       I_____________________________I   Paroxysm        \

  /___________________________>                    <_________________________\

Contents:

• Disclaimer
• Introduction
• History
• The Memory Map
• Timeline and History Chart
• Future of DOS
• Postscript
• Bibliography

Disclaimer:

Although this document is purely informative, the author claims no responsibility for any misguided souls who find a way to twist its contents into anything harmful or overly offensive.

Introduction:

When a computer is turned on an Operating System must be loaded into the computer's memory before the user can begin using it. IBM compatible machines use an operating system called MS-DOS. MS stands for "MicroSoft" (a trade name), while DOS stands for "Disk Operating System", which tells us that it's original purpose was to provide an interface between a computer and its disk drives. Technically, DOS is a high-level interface between an application program and the computer.

DOS has been extended further, allowing programs to handle the likes of simple memory management, disk operations, assorted system tasks (e.g. date/time), user input commands and managing input/output (i/o) devices (i.e. it provides operating instructions for the computer to manage both hardware and software). Versions 3.1 and up also provide basic networking functions.

Beyond this, DOS provides the user with the important facility of file and disk management (often referred to as disk-housekeeping). This part of DOS is particularly crucial to the user as it was specifically designed for him or her to interact with.

With the advent of installable device drivers and TSR (Terminate but Stay Resident) programs in DOS v2.0, the basic DOS functions could be extended to handle virtually any scale of operations required. This was the first instance of multiple programs being run at once in DOS. Some TSR's can however interfere with the running of programs. When a program is loaded into memory it assumes that it has exclusive use of this memory and will not take into account the fact that another program (the TSR) is also using this area. Thus a conflict can arise causing the program to hang (hang means that the screen freezes and the task being executed stops responding forcing the user to either switch off or reboot the computer).

History:

The development of MS-DOS/PC-DOS began in October 1980, when IBM began searching the market for a suitable operating system to go with their soon to be released IBM PC's (commercial Personal Computers). IBM had originally intended to use Digital Research's industry standard operating system - CP/M (Control Program/Monitor or Control Program for Microcomputer - originally written in 1973 by Gary Kildall in his PL/M language). This was never implemented due to uncertain reasons, the most likely being poor diplomatic relations between the two companies. Later, IBM approached a relatively small company called Microsoft, which specialised in language vending. Bill Gates and Paul Allen had written Microsoft BASIC and were selling it on punched tape or disk to early PC hobbyists.

Earlier, in April 1980, Tim Patterson began writing an operating system for use with Seattle Computer Products' 8086-based (S100 bus micros) computer. Seattle Computer Products decided to come up with their own disk operating system, due to delays by Digital Research in releasing a CP/M-86 operating system. By August 86-DOS or QDOS v0.10 (Quick and Dirty Operating System) was shipped by Seattle Computer Products. It was a 16-bit version of CP/M. Even though it had been created in only two man-months, the DOS worked surprisingly well. A week later, the EDLIN line editor was created. EDLIN was supposed to last only six months, before being replaced, but it endured for longer.

In September Tim Patterson showed Microsoft his 86-DOS, written for the 8086 chip. At this stage Microsoft had no 8086 real operating system to offer, but capitalized when, in October, Microsoft's Paul Allen contacted Patterson, asking for the rights to sell SCP's DOS to an unnamed client (IBM). Microsoft paid less than $100 000 for the rights. Patterson's DOS v1.0 was approximately 4000 lines of assembler source. This code was quickly polished up and presented to IBM for evaluation.

An agreement was reached between the two companies and IBM agreed to accept 86-DOS as the main operating system for their new PC. In February 1981, 86-DOS was run for the first time on IBM's prototype microcomputer. Furthermore, Microsoft purchased all rights to 86-DOS in July 1981.

In August, IBM announced the IBM 5150 PC, featuring a 4.77-MHz Intel 8088 CPU, 64KB RAM, 40KB ROM, one 5.25-inch floppy drive, and PC-DOS 1.0 (Microsoft's MS-DOS), for $3000.

Thus, "IBM Personal Computer DOS v1.0" was available for the introduction of the IBM PC in October 1981. IBM heavily subjected the program to an extensive quality-assurance test and found there to be well over 300 bugs and decided to rewrite the programs. This is why PC-DOS is copyrighted to both Microsoft and IBM.

Some early OEM (Original Equipment Manufacture) versions of DOS had different names such as Compaq-DOS, Z-DOS, Software Bus 86, etc. By version 2.0 Microsoft had succeeded to persuade everyone but IBM to call it MS-DOS.

It is interesting to reflect on the fact that the IBM PC was not originally meant to run MS-DOS. Instead it was supposed to use a (not yet in existence) 8086 version of CP/M. On the other hand, DOS was originally written before the IBM PC was created. CP/M-86 would have been the main operating system except for two things: Digital Research wanted $495 for CP/M-86 (considering PC-DOS was basically free) and many software developers found it easier to port software from CP/M into PC-DOS than into CP/M-86.

The IBM PC was first shipped without an operating system. IBM only started including DOS when the second generation AT/339 came out. A user could order one of three available operating systems: IBM PC-DOS, a version of UCSD p-System (type of integrated Pascal operating system - like the improved BASIC operating systems used by the Commodore 64,) and CP/M-86, which was officially an option even though it was unavailable until later on. Since IBM's $39.95 DOS was much cheaper than anyone else's it soon became the most popular.

An upgrade from DOS v3.3 to v4.0 was solely done by IBM, it was later licenced back to Microsoft. In early 1990 IBM declared that it would be ceasing development of DOS, handing the reigns over to Microsoft from then on.

Microsoft's Press' "MSDOS Encyclopaedia" illustrated an example of a late DOS v1.25 OEM brochure. Microsoft was praising future enhancement to v1.25 including XENIX-compatible pipes, process forks and multitasking, as well as "graphics and cursor positioning, kanji support, multi-user and hard disk support and networking". Despite these large aspirations, Microsoft failed to produce the forks, multitasking and multi-user support (at least in US versions of DOS).

The notice claimed: "MS-DOS has no practical limit on disk size. MS-DOS uses 4-byte XENIX OS compatible pointers for a file and disk capacity of up to 4 gigabytes."

For the record they actually delivered:

kanji support:
DOS 2.01, 2.25 (double-byte character set)
---
hard disk support:
DOS 2.0 (subdirectories)
---
networking:
DOS 3.1 (file locking support MS Networks)
DOS 6.0 (bundled Interlink in with DOS)
---

Microsoft launched an aggressive marketing campaign for MS-DOS. Early Microsoft advertisements promoted DOS' XENIX-like features and promised XENIX functionality in future releases.

Microsoft had announced their intention of building a multi-user, multitasking operating system since as early as 1982. They Shipped beta versions of "DOS 4.0" in 1986/87 before v3.3 was even announced. Microsoft UK had announced that they had licenced v4.0 to Apricot Computers and the French Postal Service was supposed to be running it.

MS-DOS and PC-DOS have been run on more than just the IBM-PC and clones:

Hardware PC Emulation:

Software PC Emulation:

DOS Emulation:

The Memory Map:

About a decade ago, standard memory configurations were 256KB, 512KB or 640KB on computers. This memory was often looked at in segments of 65536 bytes or 64KB. The user is allocated 10 segments, or 640KB and the system is allocated the remaining 6, or 384KB. The original designers of the 8088, decided that no one would ever possibly need more than 1MB of memory (yeah, right!). So they built the machine so that it couldn't access above 1 MB. To access the whole MEG, 20 bits are needed. This allows a total of 220 combinations of bits, that is 1048576 (= 1024*1024 or 1 MB) different numbers, each of which represents an address of a single byte of data. The problem was that the registers only had 16 bits, and if they used two registers, that would be 32 bits, which was way too much (they thought). So they came up with a rather brilliant (not!) way to do their addressing - they would use two registers. They decided that they would not be 32bits, but the two registers would create 20 bit addressing. And thus Segments and Offsets were created.

**Note: it helps to understand assembly code.

SEGMENT * 16    |0010010000010000----| - range (0 to 65535)*16

 +                    

OFFSET          |----0100100000100010| - range (0 to 65535)

 =

20 bit address  |00101000100100100010| - range 0 to 1048575 (1 MB)

                   \----- DS -----/

                   \----- SI -----/

                     \- Overlap-/

This shows how DS : SI is used to construct a 20 bit address.

Segment registers are: CS, DS, ES, SS. On the 386+ there are also FS & GS.

Offset registers are: BX, DI, SI, BP, SP, IP. In 386+ protected mode, any general register (not a segment register) can be used as an offset register (except IP, which isn't accessable).

If you'll notice, the value in the segment register is multiplied by 16 (or shifted left 4 bits) and then added to the offest register. Together they create a 20 bit address. Thus, there are many combinations of the segment and offset registers that will produce the same address. The standard notation for a SEGment/OFFset pair is:

Where SEGMENT = 0A000h and OFFSET = 00000h.
(This happens to be the address of the upper left pixel on a 320x200x256 screen.)
You may be wondering what would happen if you were to have a segment value of 0FFFFh and an offset value of 0FFFFh.

Notice how <0FFFFh * 16 (or 0FFFF0h ) + 0FFFFh = 1,114,095> is larger than 1,048,576 (or 1 MEG).

This means that more than 1 MB of memory is actually accessible! Well, to actually use that extra bit of memory, you would have to enable something called the A20 line, which just enables the 21st bit for addressing. This little extra bit of memory is usually called "HIGH MEMORY" and is used when you load something into high memory or say DOS = HIGH in your AUTOEXEC.BAT file or DEVICEHIGH=MOUSE.SYS in your CONFIG.SYS file (HIMEM.SYS and EMS386.EXE actually manage that).

Here is an illustration of a typical memory map:

The IBM PC handles its address space in 64k segments, divided into
16k fractions and then further as necessary:

*********************************************************************

*start *start*end  *                                                *

*addr. *addr.*addr.*                     usage                      *

*(dec) *   (hex)   *                                                *

*********************************************************************

*   *640k RAM Area*                                                 *

*********************************************************************

* 0k   *         *  start of RAM, first K is interrupt vector table *

* 16k  *0000-03FF*  PC-0 system board RAM ends                      *

* 32k  *0400-07FF*                                                  *

* 48k  *0800-0BFF*                                                  *

*********************************************************************

* 64k  *1000-13FF*  PC-1 system board RAM ends                      *

* 80k  *1400-17FF*                                                  *

* 96k  *1800-1BFF*                                                  *

* 112k *1C00-1FFF*                                                  *

*********************************************************************

* 128k *2000-23FF*                                                  *

* 144k *2400-27FF*                                                  *

* 160k *2800-2BFF*                                                  *

* 176k *2C00-2FFF*                                                  *

*********************************************************************

* 192k *3000-33FF*                                                  *

* 208k *3400-37FF*                                                  *

* 224k *3800-3BFF*                                                  *

* 240k *3C00-3FFF*                                                  *

*********************************************************************

* 256k *4000-43FF*  PC-2 system board RAM ends                      *

* 272k *4400-47FF*                                                  *

* 288k *4800-4BFF*                                                  *

* 304k *4C00-4FFF*                                                  *

*********************************************************************

* 320k *5000-53FF*                                                  *

* 336k *5400-57FF*                                                  *

* 352k *5800-5BFF*                                                  *

* 368k *5C00-5FFF*                                                  *

*********************************************************************

* 384k *6000-63FF*                                                  *

* 400k *6400-67FF*                                                  *

* 416k *6800-6BFF*                                                  *

* 432k *6C00-6FFF*                                                  *







*********************************************************************

* 448k *7000-73FF*                                                  *

* 464k *7400-77FF*                                                  *

* 480k *7800-7BFF*                                                  *

* 496k *7C00-7FFF*                                                  *

*********************************************************************

* 512k *8000-83FF*                                                  *

* 528k *8400-87FF*                                                  *

* 544k *8800-8BFF*  the original IBM PC-1 BIOS limited memory to    *

* 560k *8C00-8FFF*  544k                                            *

*********************************************************************

* 576k *9000-93FF*                                                  *

* 592k *9400-97FF*                                                  *

* 609k *9800-9BFF*                                                  *

* 624k *9C00-9FFF* to 640k (top of RAM address space)               *

* 639k *         * some RLL and SCSI hard disk adapters, some four  *

*      *         * floppy controller cards, some AMI and PS/2 BIOS, *

*      *         * and assorted other cards sometimes try to use the*

*      *         * last K for storing temporary data.  This can     *

*      *         * cause trouble with programs which assume they    *

*      *         * have a full 640k, and will prevent backfilling   *

*      *         *  memory with some memory managers.  Beware!      *

*********************************************************************

*A0000 ***** 64k ***** EGA/VGA starting address                     *

*A0000 ***** 64k ***** Toshiba 1000 DOS ROM (MS-DOS 2.11V)          *

*********************************************************************

* 640k *A0000-A95B0*  MCGA 320x200 256 color video buffer           *

*      *     -AF8C0*  MCGA 640x480 2 color video buffer             *

*      *     -A3FFF*                                                *

* 656k *A4000-A7FFF*                                                *

* 672k *A8000-ABFFF*this 64k segment may be used for contiguous DOS *

* 688k *AC000-AFFFF*RAM with appropriate hardware and software      *

*********************************************************************

*B0000 ***** 64k ***** mono and CGA address                         *

*********************************************************************

* 704k *B0000-B3FFF*4k  mono display | The PCjr and early Tandy 1000*

* 720k *B4000-B7FFF*                 | BIOS revector direct write to*

* 736k *B8000-BBFFF*16k CGA          | the B8 area to the Video Gate*

* 756k *BC000-BFFFF*                 | Array and reserved system RAM*

*********************************************************************

*C0000 ***** 64k *************** expansion ROM                      *

*********************************************************************

* 768k *C0000-C3FFF*16k EGA BIOS C000:001E EGA BIOS signature       *

*      *           *    (the letters 'IBM')                         *

*      *C0000-C7FFF*32k VGA BIOS extension (typical)                *

* 784k *C4000-C5FFF*                                                *

*      *C6000-C63FF*256 bytes IBM PGC video communications area     *

*      *C6400-C7FFF*                                                *

* 800k *C8000-CBFFF*16k hard disk controller BIOS, drive 0 default  *

*      *CA000      *    some 2nd floppy (HD) controller BIOSes      *

* 816k *CC000-CDFFF* 8k IBM PC Network NETBIOS                      *

*      *CE000-CFFFF*                                                *

*********************************************************************

*D0000 ***** 64k ***** expansion ROM                                *

*********************************************************************

* 832k *D0000-D7FFF*32k IBM Cluster Adapter  | PCjr first ROM cart. *

*      *      DA000*voice communications     | address area.        *

* 848k *D4000-D7FFF*                         | Common EMS board     *

* 864k *D8000-DBFFF*                         | paging area.         *

*      *D8000-DBFFF* IBM Token Ring default Share RAM address       *

*      *DC000      * IBM Token Ring default BIOS/MMIO address       *

* 880k *DC000-DFFFF*                         |                      *

*      *DE000      *4k  TI Pro default video buffer                 *

*********************************************************************

*E0000 ***** 64k ***** expansion ROM                                *

*                      wired to ROM sockets in the original IBM AT  *

*                      used by ABIOS extensions on some PS/2 models *

*********************************************************************

* 896k *E0000-E3FFF*                         | PCjr second ROM cart.*

* 912k *E4000-E7FFF*                         | address area         *

* 928k *E8000-EBFFF*                         |                      *

* 944k *EC000-EFFFF*                         | spare ROM sockets on *

*      *           *                         | IBM AT (reserved in  *

*      *           *                         | hardware)            *

*********************************************************************

*F0000 ***** 64k ***** system                                       *

*********************************************************************

* 960k *F0000-F3FFF*reserved by IBM          | cartridge address    *

* 976k *F4000-     *                         | area (PCjr cartridge *

*      *F6000      *ROM BASIC Begins         | BASIC)               *

* 992k *F8000-FB000*                         |                      *

* 1008k*FC000-FFFFF*ROM BASIC and original   |                      *

*      *           *BIOS (Compatibility BIOS |                      *

*      *           *in PS/2)                 |                      *

* 1024k*      FFFFF*end of memory (1024k) for 8088 machines         *

*********************************************************************

* 384k *100000-15FFFF* 80286/AT extended memory area, 1Mb mbd.      *

* 15Mb *100000-FFFFFF* 80286/AT extended memory address space       *

* 15Mb *160000-FDFFFF* Micro Channel RAM expansion (15Mb ext. mem)  *

* 128k *FE0000-FFFFFF* system board ROM        (PS/2 Advanced BIOS) *

*********************************************************************

*  64k *C0000000-C000FFFF* Weitek "Abacus" math coprocessor         *

*      *                 * memory-mapped I/O                        *

+*******************************************************************+

Timeline:

In May 1982, Microsoft released MS-DOS v1.1 to IBM, for the IBM PC. It supported 320KB double-sided floppy disk drives. Microsoft also released MS-DOS v1.25, similar to v1.1 but for IBM-compatible computers.

In March 1983, MS-DOS v2.0 for PCs is announced. It was written from scratch, supporting 10 MB hard drives, a tree-structured file system, and 360 KB floppy disks. October saw IBM introducing PC-DOS v2.1 with the IBM PCjr.

In March 1984, Microsoft released MS-DOS v2.1 for the IBM PCjr. Microsoft released MS-DOS v2.11 a short time later. It included enhancements to better allow conversion into different languages and date formats. In August, Microsoft released MS-DOS v3.0 for PCs. It added support for 1.2MB floppy disks, and bigger (than 10 MB) hard disks. In November, Microsoft released MS-DOS v3.1, adding support for Microsoft networks.

In January 1986, Microsoft released MS-DOS v3.2. It added support for 3.5-inch 720 KB floppy disk drives. Microsoft released MS-DOS v3.25 as well.

In April 1987, IBM announced DOS v3.3 for PCs, for $120. In August Microsoft shipped MS-DOS v3.3. In November Compaq shipped MS-DOS v3.31 with support for over 32MB drives.

In 1988 Digital Research transformed CP/M into DR DOS. In June Microsoft released MS-DOS v4.0, including a graphical/mouse interface. In July IBM shipped DOS v4.0, which included a shell menu interface and support for hard disk partitions over 32 MB. In November Microsoft released MS-DOS v4.01.

In April 1990, Microsoft introduced Russian MS-DOS v4.01 for the Soviet market.
May saw Digital Research releasing DR DOS v5.0.

In June 1991, Microsoft released MS-DOS v5.0. It added a full-screen editor, undelete and unformat utilities and task swapping. GW-BASIC is replaced with Qbasic, based on Microsoft's QuickBASIC. In September Digital Research Inc. releases DR DOS v6.0, for $100.

In March 1993, Microsoft introduced the MS-DOS v6.0 upgrade, including DoubleSpace disk compression. 1 million copies of the new and upgraded versions were sold through retail channels within the first 40 days. In November, Microsoft released MS-DOS v6.2.

In February 1994, Microsoft released MS-DOS v6.21, removing DoubleSpace disk compression. April IBM releases PC-DOS v6.3. In June Microsoft releases MS-DOS v6.22, bringing back disk compression under the name DriveSpace.

In February 1995, IBM announced PC DOS v7, with integrated data compression from Stac Electronics (Stacker). In April, IBM released PC DOS v7. In August of 1995 Microsoft introduced Windows 95, it included MS DOS v7.0 but it's clear that DOS is going to remain a constant for several years to come.

DOS HISTORY CHART: (system file sizes in bytes)

**Note: Microsoft had no official version of MS DOS prior to DOS 3.2. Only OEM versions were sold with the PC by the computer manufacture.

Future of DOS:

At first, many people would answer saying that DOS has no future. It has seen it's heyday and now it's up to high-resolution GUI's (Graphic User-Interfaces - e.g. Windows 95) to lead the operating system pack. But let's not be too quick to dismiss it. There are many reasons why DOS is an essential part of many of today's finest systems.

Talk to mainstream computer industry "specialists" and they'd have you believe that there is no longer any place for it. Why? Because they don't understand the special speed and performance requirements unique to systems other than "supercomputers with neuro-networking". I'm talking about the many hundreds of thousands of users that depend on older systems to support their businesses. Low-tech industries rely heavily on computers with old versions of DOS installed on them. The average "business person" here doesn't need anything better than a 486SX with 8MB of RAM to run their MS-DOS based accounting program. This shouldn't be made redundant just because DOS is so-called "outdated". This is also where the highest resistance to the removal of DOS has come from.

Despite this, many people believe that old DOS programs are becoming redundant because they are not Y2K compliant. But I say that DOS programs are simplistic by nature and can easily be patched to be compatible. Even that seems more sensible than installing Windows and taking up copious quantities of HD space with utilities that have a hundred times more features than you'll ever figure out, let alone use. Don't even get me started on the redundant registry entries and .dll files that remain after 'removing' shareware and evaluation software on Win95. You won't get any of that in DOS!

Win95 and DOS can be compared to bank notes and coin-change respectively. Win95 caters for the multiuser/multitasking system which has convenience similar to the spending of large bank notes. DOS caters for the single-task user without the need of extraneous functions and add-ons. Like coins, DOS adds up for too many individuals not to have a large economic impact if it were removed.

One of the great 'new features' of Win95 is it's Recycle Bin (thanks Mac!). But if it's so great, what does a user do if he or she wants to recover a file after having emptied the bin? Nothing? Tough luck? Nope. DOS to the rescue! The user simply needs to 'Restart in MS-DOS mode', type in and confirm the LOCK command, go to the directory where the file was stored (or 'c:\recycled') and undelete it using DOS v6.2x's old UNDELETE.EXE (remember: restart the computer or type in UNLOCK to proceed safely). Conclusion: Windows couldn't have been used to retrieve that 'permenantely' deleted file without using extraneous software (eg. Norton Utilities).

Okay, so I've been heavy-handed about my support for DOS over Windows. Sue me, I like it - it's my 'oldschool'. ;) Although...

Many people support DOS in that they perceive it to be a magical operating system that is just perfect for games. Well I have a challenge for them - TRY PROGRAMMING FOR IT! I'll bet money that half the reason why Interplay's relatively new game "DTUM" didn't ship with network options was simply because it is a DOS game and they would have had to do the bulk of the work themselves. Simply put: if Microsoft wants to write network code for game developers (via Direct Play) or add support to most if not all sound cards (Direct Sound), a designer would be foolish not to take advantage of it. Thus guaranteeing MS role in the games market. Even the mighty Quake(TM) released Windows/OpenGL versions (sell out? - you decide).

Two factors determine the user's productivity: how long it takes to tell the computer to do something, and how long the computer takes to do it. The former is largely dependent on how you've customized your system with shortcuts, macros, and AutoLISP routines and the platform is not particularly relevant. The latter is partly dependent on your choice of platform - any kind of Windows inevitably suffers compared with DOS. Why? Because DOS remains on a lower user level compared to Win95 and thus keeps more of the system's resources free.

Even Windows 98 - the most recent operating system released by Microsoft to date retains elements of DOS for users - obviously Microsoft recognises the great need for it. These elements, however, aren't pure DOS. They're part of Win95/98. A shell (pardon the pun) of its former self if you will. The question is, will Win98 be able to run without these elements? One of the intriguing questions being asked today since the discovery that Win95 works with DR-DOS 7.01, is how dependent on DOS is/was Win95? I would have called this myth until I went to fix a Win95 problem and by accident discovered that Win95 appears and runs on top of DOS.

So was it, in fact, essential for Microsoft to retain DOS? Was Win95 already so intricately (/technically) dependent on DOS that the Win98 upgrade wouldn't work without it? Probably not, although speculation is widespread.

I believe that DOS will remain for a few years to come at least. Sentimentality alone can't keep it around forever though and it's only a matter of time before somebody finds a way of phasing it out completely. But not without meeting resistance from individuals for which DOS provides an efficient service. As a DOS junkie, I find it's faster to type many commands or use batch files than having to click and move files around in Windows. What can I say? The mouse slows me down and I think 'user-friendliness' is a sham.

Postscript:

I know what many of you are thinking and I agree: MS OS's suck, get Linux. =)

Bibliography:

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