C:\> and Beyond: From MS-DOS to Windows NT and Windows 2000

Hi there! It's BOB.

Every time you open a command prompt and type dir, or wonder why your drive is called C:, or log into a domain controller, you're touching forty-plus years of history.

Today, let's take a quick trip through the family tree: MS-DOS, Windows NT, and Windows 2000, the version that gave us Active Directory. Grab a snack, this goes back a while. 🍿

Part 1: MS-DOS, the Quick and Dirty Beginning

A $75,000 bargain

In 1980, IBM was building its first personal computer and needed an operating system. Microsoft didn't have one. But a small Seattle company, Seattle Computer Products, did. A programmer there named Tim Paterson had written one, nicknamed QDOS ("Quick and Dirty Operating System") and later called 86-DOS.

Microsoft licensed 86-DOS for $25,000 in late 1980, then bought all the rights for another $50,000 in July 1981, just a month before IBM's PC launched. IBM sold it as PC DOS 1.0, and Microsoft sold its own version to other computer makers as MS-DOS.

That's about $75,000 for the foundation of an empire. Best shopping trip ever. (Seattle Computer Products later sued, and settled for $1 million.)

Growing up, one version at a time

After that, MS-DOS didn't disappear. It hid inside Windows 95, 98 and Me, quietly booting the computer before Windows took over.

Why your drive is still C:

In the early days, A: and B: were the floppy drives. When hard disks came along, they got the next letter, C:. Floppies are long gone, but C: is still the home of Windows today. MS-DOS is in your computer's DNA! 🧬

MS-DOS is open source now!

Here's a fun one for lab folks: Microsoft has released the source code for MS-DOS 1.25, 2.0 and 4.0 on GitHub under the MIT license (4.0 arrived in April 2024, together with IBM). You can read the actual assembly code that ran on millions of PCs. Some of the comments are delightful.

Part 2: Windows NT, the Serious Sibling

While MS-DOS and the early versions of Windows ran on home PCs, Microsoft knew they had limits. One crashed program could take down the whole machine, and there was barely any security at all.

Microsoft needed a serious operating system. So in 1988, it hired Dave Cutler, a legendary engineer from Digital Equipment Corporation (DEC) who had led work on DEC's VMS operating system, along with a group of his team.

The new system was first planned as OS/2 3.0 (a joint project with IBM), but Microsoft went its own way and called it Windows NT. What does NT stand for? Officially it was "New Technology," though there's a fun theory it came from the Intel i860 chip it was first developed on, code-named N10 ("N-Ten"). By 1998, Bill Gates said the letters didn't mean anything anymore. 🤷

What made NT special

• Protected memory. Programs got their own space, so one crash didn't sink the ship.
• Real security. User accounts, permissions on files and folders, and an audit log.
• NTFS, a much sturdier file system than DOS's FAT.
• Portability. NT ran on several kinds of processors: Intel x86, MIPS and DEC Alpha, with PowerPC added in NT 3.51. A special layer called the Hardware Abstraction Layer (HAL) made that possible.
• Domains. NT servers could manage users for a whole network of computers.

The NT family

NT 4.0 became the business server for years. If you were an IT person in the late '90s, you probably spent a lot of time with User Manager for Domains and Server Manager, and a lot of time rebooting after installing anything.

Part 3: Windows 2000, the One That Changed Everything

Windows NT 5.0 got a new name in 1998: Windows 2000. It arrived on February 17, 2000, in four editions: Professional, Server, Advanced Server and Datacenter Server.

And it brought a list of features you still use every single day in your lab:

• 🌳 Active Directory. The big one! A directory based on LDAP and DNS, with domains, trees, forests and OUs, replacing NT 4.0's flat domains.
• 📜 Group Policy. Manage thousands of computers' settings from one place.
• 🔐 Kerberos for signing in, instead of NT's older NTLM.
• 🔌 Plug and Play and proper power management, finally on the NT side of the family.
• 💾 NTFS 3.0, with disk quotas and file encryption (EFS).
• 📮 Certificate Services, the grandparent of the AD CS you might be running today.

Windows 2000 Professional also brought NT's stability to regular desktops, setting the stage for Windows XP to finally merge the home (DOS-based) and business (NT-based) families in 2001.

Windows 2000's extended support ended on July 13, 2010.

Why It Still Matters in Your Lab

Every Windows you run today, from Windows 11 to Windows Server 2025, is still a Windows NT. A few things you'll bump into that come straight from this history:

• C:\, drive letters, and dir in the command prompt (thanks, DOS!).
• NTFS and its permissions (thanks, NT!).
• The NetBIOS domain name (LAB\username), a leftover from NT 4.0 domains.
• Active Directory, Group Policy and Kerberos (thanks, Windows 2000!).
• Even the version number. Run [Environment]::OSVersion in PowerShell and you'll still see NT hiding in there.

💡 BOB's tip: Want to feel the history? FreeDOS (a free, open-source DOS) and old Windows versions run happily in a Proxmox VM. Just keep retro VMs off your real network, since they haven't had a security update since before some of you were born!

Wrapping Up

• MS-DOS started as 86-DOS, bought for about $75,000, and ran the PC world for over a decade.
• Windows NT brought real security, protected memory and NTFS, built by Dave Cutler's team.
• Windows 2000 gave us Active Directory, Group Policy and Kerberos, the foundation of every Windows domain since.
• Every Windows today is still an NT at heart, with a little bit of DOS in its DNA.

See you next time!

— BOB

Sources

• Wikipedia: 86-DOS
• Wikipedia: MS-DOS
• GitHub (Microsoft): MS-DOS source code
• Microsoft Open Source Blog: Open sourcing MS-DOS 4.0
• Wikipedia: Windows NT
• Wikipedia: Windows NT 3.1
• Wikipedia: Windows 2000
• Wikipedia: Dave Cutler
• FreeDOS project: freedos.org