Learn MS-DOS (Part 6) - Configuration & Environment Commands in MS-DOS

🖥 Introduction

By now, we’ve learned how to work with files, folders, disks, and system information. But MS-DOS is more than just commands — it’s an environment you can configure and personalize.

Configuration & environment commands are like the settings panel of DOS. They control how the system looks, how it starts up, and how programs interact with the operating system.

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🔹 1. SET – Set Environment Variables

Purpose: Creates, changes, or displays environment variables.

Syntax:

SET [variable=[string]]

Examples:

SET

Displays all environment variables.

SET PATH=C:\DOS;C:\UTILS

Sets the PATH so DOS can find programs in C:\DOS and C:\UTILS.

SET USER=DADDY

Creates a variable USER with value DADDY.

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🔹 2. PATH – Define Search Path for Programs

Purpose: Tells DOS where to look for executable files.

Syntax:

PATH [directory;...]

Examples:

PATH

Displays the current search path.

PATH C:\DOS;C:\APPS

Adds C:\DOS and C:\APPS to the search path.

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🔹 3. PROMPT – Customize the Command Prompt

Purpose: Changes the text of the DOS prompt.

Syntax:

PROMPT [text]

Special Codes:

• $P → Current drive & path

• $G → Greater-than sign (>)

• $D → Current date

• $T → Current time

Examples:

PROMPT $P$G

Sets prompt to show current drive and path like C:\WORK>

PROMPT HelloDaddy$G

Sets prompt as HelloDaddy>

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🔹 4. AUTOEXEC.BAT – Startup Batch File

Purpose: Runs automatically at boot and sets up environment.

• Located at the root of the boot drive (C:).

• Typically contains commands like PATH, SET, or programs to load at startup.

Example AUTOEXEC.BAT content:

@ECHO OFF
PROMPT $P$G
PATH C:\DOS;C:\UTILS
SET TEMP=C:\TEMP

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🔹 5. CONFIG.SYS – System Configuration File

Purpose: Loads device drivers and system settings during boot.

• Located in the root of the boot drive.

• Works alongside AUTOEXEC.BAT.

Common Commands in CONFIG.SYS:

• DEVICE= → Load a driver

• FILES= → Set max open files

• BUFFERS= → Set disk buffers

Example CONFIG.SYS content:

DEVICE=C:\DOS\HIMEM.SYS
FILES=30
BUFFERS=20

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🔹 6. LOADFIX – Load Programs Above 64K

Purpose: Loads a program above the first 64K of memory, avoiding memory allocation issues.

Syntax:

LOADFIX [program] [arguments]

Example:

LOADFIX GAME.EXE

Runs GAME.EXE with memory fix applied.

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🔹 7. LOADHIGH (LH) – Load Program into Upper Memory

Purpose: Loads a program into high memory to free up conventional memory.

Syntax:

LOADHIGH [program]

Example:

LH MOUSE.COM

Loads mouse driver into upper memory.

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🔹 8. DEVICE / DEVICEHIGH – Load Drivers

Purpose: Loads device drivers from CONFIG.SYS, optionally into high memory.

Examples (in CONFIG.SYS):

DEVICE=C:\DOS\ANSI.SYS
DEVICEHIGH=C:\DOS\RAMDRIVE.SYS

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🧰 Bonus Tips

• Always use PROMPT $P$G in AUTOEXEC.BAT — it’s the most practical setup.

• PATH and SET are crucial for making programs run smoothly.

• AUTOEXEC.BAT and CONFIG.SYS were the backbone of DOS customization.

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✅ Conclusion

Configuration & environment commands turn MS-DOS from a plain system into your personal workspace. They let you define paths, set environment variables, and control how DOS boots and behaves.

👉 Next in Part 7, we’ll explore Networking Commands — how DOS connected computers in the early days of networking.