Introduction to operating systems (MS-DOS commands, internal and external)

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1️⃣ Introduction to Operating Systems (OS) 🖥️

Definition:
An Operating System (OS) is system software that manages computer hardware and software resources and provides common services for computer programs.

Functions of an OS:

  1. Process Management ⚙️ – Handles running programs and tasks

  2. Memory Management 🧠 – Allocates RAM efficiently

  3. File Management 📁 – Organizes, stores, and retrieves files

  4. Device Management 🖨️ – Manages input/output devices

  5. Security & Access Control 🔒 – Protects data from unauthorized access

  6. User Interface 🖱️ – Provides GUI or CLI for users

Examples: Windows, Linux, macOS, MS-DOS

2️⃣ Introduction to MS-DOS 💻

  • MS-DOS (Microsoft Disk Operating System) is a command-line based OS

  • It is text-based and operates using commands

  • Commands are classified as: Internal and External

3️⃣ MS-DOS Commands ⌨️

A. Internal Commands 🔹

  • Stored in memory (COMMAND.COM)

  • Can be executed without external files

  • Common Internal Commands:

CommandUse
DIRLists files and directories
CD / CHDIRChange directory
MD / MKDIRCreate new directory
RD / RMDIRRemove directory
COPYCopy files
DEL / ERASEDelete files
REN / RENAMERename files
TYPEDisplay contents of a file
CLSClear the screen
DATEDisplay/change date
TIMEDisplay/change time

B. External Commands 🔹

  • Stored in **disk (files like *.COM, .EXE, .BAT)

  • Loaded from disk when executed

  • Common External Commands:

CommandUse
FORMATFormat a disk
DISKCOPYCopy contents of one disk to another
CHKDSKCheck disk for errors
XCOPYCopy files and directories recursively
BACKUPBackup files to disk
RESTORERestore files from backup
EDITText editor to create/edit files
ATTRIBView/change file attributes
FDISKPartition hard disk

4️⃣ Practical Tips for MS-DOS 🛠️

  • Commands are not case-sensitive

  • Use /? after any command for help
    Example: COPY /?

  • Use TAB for auto-completion of filenames

  • Use UP / DOWN arrows to scroll through previous commands

5️⃣ Key Notes

  • Internal commands → Always available in memory

  • External commands → Need to be present on disk to execute

  • MS-DOS is a good base for learning OS and file management

  • Modern OS like Windows uses GUI, but underlying commands still work in Command Prompt

💡 Tip: Think of Internal commands as built-in tools and External commands as optional tools you bring from disk.

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