The Start of an Empire: MS-DOS Celebrates 30th Birthday
A small software company acquired the license to the QDOS operating system on July 27, 1981 and laid the foundation for an empire that would dominate the computer software world.
Bill Gates and Paul Allen spent $75,000 for QDOS and began selling sub-licenses for $47,500 in 1981 and $95,000 after that.
IBM was the first customer and received a slightly modified version of MS DOS 1.0 that was offered as PC DOS and sold by IBM for $40. However, Microsoft had sold IBM DOS and BASIC for $400,000 before they actually had access to the DOS operating system. Gates and Allen originally had planned to sell IBM their own Xenix OS, which was derived from UNIX and designed for Intel's 8086 processor, while IBM decided to go with Intel's 8088 CPU instead. Microsoft's solution eventually surfaced as QDOS.
While Microsoft turned DOS into a massive success, Tim Paterson is considered to be the inventor of DOS and wrote the first versions of MS DOS, up to version 1.25. Paterson got out of school in 1978, joined Seattle Computer products and had DOS running on prototypes by January 1979.
Gates initially estimated that IBM could sell about 200,000 DOS PCs, but more than 1 million were eventually sold by the end of 1984. Those first commercial PCs integrated Intel's 8088 processor and ran at 4.77 MHz. The first DOS PC, however, was offered by Seattle Computer products as a set of plug-in cards, including a 8086 CPU card.
Seattle Computer Products wanted $150,000 for the QDOS license, but was convinced by Gates to give it away for $50,000 as well as a $25,000 license fee from a customer that Microsoft kept secret. Sub-licenses for MS-DOS created the first windfall for the young company. In 1981, Microsoft had more than 15 million in revenue.

Playing jokes like...
prompt I know your going to just play strip poker again
and...
edit autoexec.bat
@echo off
attrib +h config.sys
attrib +h command.com
echo stop touching me!!!
echo I remember back in the day of editing the autoexec and the command.com files just to load the programs that needed all of my 2 megs (yes, two 2 megabytes) of memory. Computers sure have come a long way since my 386 SX-15 (15 MHz) with Windows 3.1 and DOS 5.0.
Playing jokes like...
prompt I know your going to just play strip poker again
and...
edit autoexec.bat
@echo off
attrib +h config.sys
attrib +h command.com
echo stop touching me!!!
(dot-matrix printer noises)
HIMEM.SYS is testing extended memory...done.
Add LASTDRIVE=Z so then MS-DOS recognizes some CD-ROM drives like Creative :-)
I found it useful even in XP for some office network mapping on boot (net use lpt3: \\*server name*\hplj4050 - because this old lawyer still likes to use WordPerfect 3.0), but I haven't touched it since 7.
I don't remember exactly how old I was, under 10, and so impressed with myself learning how to partition a 20MB HDD and unzip files!
Used to BBS it up in Davis CA!
But all that time spent tinkering then, really impresses people when you open the command prompt and start flying around doing dir /s /ah /p commands and finding all kinds of files they didn't know existed.
the good old days!
On the Sperry PCs I had to move the format.com to a different folder and create a format.bat because people kept trying to format the floppy drive and were formatting the 10mb or 20mb hard drives instead.
Were those the "good old days"? LOL
I remember using DOS since Windows 3.1. It brings a lot of souvenirs back into memory ^^ Just prior Windows 3.1, I did not have any way to stock data other than the ridiculous amount of ram available. Playing Sim City 2000 would have been an overkill but also better game than those I had on my Commodore 64/128 (owned both)!! Oh well time has changed quite a bit.