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# A short DOS primer

## The PC is not a console

To use a game console from the 1980s and 90s, you only needed to know three things: how to hook it up to the TV, how to insert a cartridge, and how to turn the thing on and off. That’s it!

In contrast, IBM PC compatibles running the DOS operating system are much more complex beasts. While DOSBox Staging vastly simplifies things and takes the major hurdles out of the equation, you are still expected to have a minimum understanding of the hardware and the platform to get the most out of it.

This primer intends to give you a very compressed crash-course — just enough to be able to run DOS games effectively. While this is enough to get started, we encourage you to expand your knowledge on the subject over time in the areas you’re interested in.

## Modularity

Unlike game consoles and most home computers of the era, IBM PC compatibles have a highly modular architecture. The CPU, video card, sound card, memory, and storage are all separate, interchangeable components connected through expansion slots and standardised buses. This “mix and match” design means that no two PCs were necessarily identical — the same game might run on wildly different hardware configurations.

This modularity is what makes DOS configuration more complex than simply inserting a cartridge: a game needs to know which sound card you have, how much memory is available, what video standard your graphics card supports, and so on. DOSBox Staging handles most of this automatically, but understanding the basic building blocks helps when things need tweaking.

## CPU

The heart of every IBM PC compatible is the CPU. The original IBM PC released in 1981 used the Intel 8088 processor running at 4.77 MHz. That’s extremely slow by today’s standards — about 150,000 times slower than an average smartphone from 2025! Over the course of the DOS era, CPUs evolved rapidly through the 8086, 80286, 80386, 80486, and finally the Pentium family in the mid-1990s. Each generation brought major speed increases and new capabilities.

Rather than emulating a specific CPU clock speed, DOSBox Staging uses a “cycles” system that controls how many instructions, or CPU cycles, are executed per millisecond. This is analogous to CPU speed — more CPU cycles per millisecond means a faster emulated computer. The default settings work well for the vast majority of games, but some titles require specific speed ranges to run correctly.

See CPU settings for CPU cycle ranges per DOS-era and how to fine-tune speed. The Getting Started guide walks you through a few a practical examples of adjusting the CPU speed for specific game.

- Passport to Adventure
- Beneath a Steel Sky
- Star Wars Dark Forces

## Video

The original IBM PC supported only two graphics standards: monochrome Hercules and CGA (Color Graphics Adapter) with just four colours at 320×200. EGA (Enhanced Graphics Adapter) raised this to 16 colours in 1984, and VGA (Video Graphics Array) arrived in 1987 with 256 colours at 320×200 — the resolution most DOS games are remembered for. Later SVGA cards pushed to higher resolutions and colour depths.

The Tandy 1000 line deserves special mention: it offered 16-colour graphics and three-voice sound in an affordable package, making it the best overall gaming PC until about 1987. Many mid-1980s games look and sound noticeably better in Tandy mode.

Because DOS games were designed for CRT monitors, DOSBox Staging includes CRT emulation shaders that reproduce the look of the original hardware. This makes a surprisingly large difference — pixel art that looks harsh and blocky on a modern flat panel comes alive with the subtle blending and scanlines of the CRT emulation.

See Graphics adapters for details on each emulated adapter, and Rendering for shader and display options. The Getting Started guide covers choosing a graphics adapter and aspect ratios with practical examples.

## Audio

The original IBM PC had no dedicated sound hardware, just a tiny PC speaker designed to produce simple beeps and square-wave tones. Clever programmers pushed it further and managed to coerce it to play back digitised sound samples, but it was never designed for quality audio reproduction.

The Tandy 1000 was again ahead of its time, providing three-voice sound via a built-in chip that made it the best gaming PC for sound until dedicated sound cards arrived.

Real audio came to the PC platform in the late 1987 with the AdLib card using FM synthesis, followed by Creative’s Sound Blaster in 1989 which added digital audio playback. The Sound Blaster became the de facto standard, and most DOS games from 1990 onwards support it. For high-end music, the Roland MT-32 sound module offered stunning realistic-sounding audio from 1988 onwards, though it was expensive and remained a luxury item.

The Gravis UltraSound (GUS), released in 1992, took a different approach by using wavetable synthesis with actual sampled sounds stored in its onboard RAM, producing much more realistic audio than FM synthesis. It gained a cult following, particularly in the demoscene, but never achieved the Sound Blaster’s market dominance.

General MIDI standardised a common set of 128 instrument sounds, allowing games to sound consistent across different MIDI-compatible devices. The Roland Sound Canvas SC-55, released in 1991, became the de facto reference device for General MIDI game music and is still considered the gold standard for many DOS game soundtracks.

By the mid-1990s, CD-ROM audio (CD-DA) gave games access to studio-quality 16-bit 44.1 kHz music played directly from the game disc. This bypassed the sound card entirely for music, delivering a dramatic leap in audio fidelity.

See Sound overview for a guide to selecting the best audio option for each era. The Getting Started guide walks through configuring sound devices and setting up Roland MT-32 sound step by step.

## Input peripherals

The standard input peripheral for the IBM PC compatibles was the keyboard for a long time. Eventually, the mouse gained popularity, but it wasn’t a standard accessory like on the Commodore Amiga or Apple Macintosh line of computers.

Many DOS games also support analog joysticks. Digital joysticks were a rarity on the platform.

See Input overview for keyboard, mouse, and joystick configuration, and the Key mapper for remapping controls.

## Storage

The IBM PC line of computers were initially intended for business use, therefore hard drives were standard accessory. They were optional on the first IBM PC models, and starting from the XT released in 1983, 10 to 20 MB hard drives were included as standard equipment. (Yes, you read that right, that’s megabytes! Such a hard drive could only store a couple of MP3 files or high-resolution images…)

The cost of hard drives were initially astronomical, so most home users could not afford them. This lead to the development of games that could be run from floppy disks in the early days of the PC. There is even a special class of self-booting floppy games that can be run even without an operating system present; these are referred to as “PC booter” games.

Eventually, hard drives went down in price so most people could afford them. As a result of this, the vast majority of DOS games and applications can be installed easily onto the hard drive.

By the mid-1990s, CD-ROM drives became standard equipment, vastly expanding storage capacity. Many later DOS games shipped on CD-ROMs, enabling full-motion video, CD audio soundtracks, and voice acting.

This is in stark contrast with the home computers of the era that used magnetic tapes and floppies for storage due to cost considerations well into the 1990s.

See Storage for details on drive letters, mounting directories and disk images, and the different media types. The Getting Started guide demonstrates setting up a game directory and mounting a CD-ROM image.

## Memory

The first line of IBM PC XT computers only supported up to 640 KB of memory. Later on, various solutions were invented to circumvent this limitation and make extra memory available to DOS programs. The maximum amount of memory DOS can handle is 64 MB, but games rarely could use more than 32 MB.

Frankly, DOS memory management is a complex, confusing, and often frustrating topic — no one enjoyed dealing with this stuff back in the day. The good news is that you don’t need to know much about it to use DOSBox Staging effectively. The vast majority of games and applications work well with the default 16 MB of memory, and usually there is no advantage to changing this.

See Memory management to learn more.

## MS-DOS

MS-DOS (Microsoft Disk Operating System) is the operating system that gives the platform its name. It provides the basic services needed to run programs: managing files on disk, loading programs into memory, and handling input/output to hardware devices.

MS-DOS was released in 1981 alongside the original IBM PC and went through many versions, the last being 6.22 in 1994. Each version added features (e.g., subdirectory support in 2.0 in 1983, memory management in 5.0 in 1991), but all maintained backward compatibility.

DOS is a command-line operating system, there is no graphical desktop. You interact with it by typing commands at a prompt (e.g., the famous `C:\>` prompt). Basic navigation involves commands like `DIR` to list files, `CD` to change directories, and typing a program’s name to run it. This is also how you launch most games: navigate to the game’s directory and run its executable.

DOSBox Staging emulates a DOS-compatible environment, so you don’t need to install MS-DOS separately. The emulated DOS command line works just like the real thing.

The Getting started guide gives you a gentle introduction to using DOS to configure and launch games. See DOS commands for a list of all available commands, and DOS to learn how to customise the emulated DOS environment.

## Windows 3.1

Wait a minute, isn’t this supposed to be about DOS?

That’s correct, but early Windows versions 1.0 to 3.1 were not true operating systems, only operating environments implemented as DOS programs. DOSBox Staging fully supports Windows 3.1, giving you access to the large catalogue of early CD-ROM games and educational multimedia applications. It also has partial support for Windows versions 1.0 and 2.0.

Head over to Running Windows 3.1 to learn more.