Software & Operating System notes for competitive exams (SSC, Banking, Railway) — types, functions, OS examples & quick revision tables.
Table of Contents
What is Software?
Software is a set of instructions/programs that tells the computer what task to perform. It is the intangible (“soft”) part of a computer — it cannot be touched, only used or seen (unlike Hardware).
Software = Programs + Data + Documentation
Key Characteristics:
- Intangible in nature
- Controls and directs the hardware
- Can be easily modified/updated
- Can be copied (this is why copyright/licensing issues arise)
Types of Software (Very Important)
SOFTWARE
|
---------------------------------
| |
System Software Application Software
| |
--------------------- -------------------
| Operating System | | General Purpose |
| Language | | Specific Purpose |
| Translator |
| Utility Software |
| Device Drivers |
| Firmware |
System Software
System software acts as a bridge between hardware and the user. It is essential for the basic functioning of a computer.
| Type | Function | Example |
|---|---|---|
| Operating System | Interface between hardware and software | Windows, Linux, macOS |
| Language Translator | Converts high-level code into machine code | Compiler, Interpreter, Assembler |
| Utility Software | Maintenance and optimization | Antivirus, Disk Cleanup, WinRAR |
| Device Driver | Connects a specific hardware device to the OS | Printer driver, Graphics driver |
| Firmware | Permanently stored software in ROM | BIOS |
Language Translators — 3 Types (Important MCQ Point):
- Compiler — Converts the entire program into machine language at once (faster execution, shows all errors together). Example: C, C++
- Interpreter — Converts and executes code line-by-line (slower, shows errors immediately). Example: Python, BASIC
- Assembler — Converts assembly language into machine language
Application Software
Application software is designed for specific tasks/needs of an end-user.
| Type | Example |
|---|---|
| General Purpose | MS Word, Excel, PowerPoint |
| Specific Purpose | Payroll system, Railway reservation system |
| Utility-based Application | Media player, Games |
Trick to remember: System Software = “To run the computer” | Application Software = “To do the user’s work”
Freeware, Shareware, and Open Source (Exam Favorite)
| Term | Meaning | Example |
|---|---|---|
| Freeware | Free of cost, but source code is NOT available | Adobe Reader, Skype |
| Shareware | Free for a trial period, payment required afterward | WinRAR (trial version) |
| Open Source | Free + source code available, can be modified | Linux, LibreOffice, Mozilla Firefox |
⚠️ Note: Freeware ≠ Open Source — this is a common confusion tested in exams!
What is an Operating System (OS)?
Definition: The OS is a system software that manages computer hardware and provides an interface for the user to interact with it. It is the first thing loaded when a computer starts (booting).
OS = “Manager/Boss of the Computer”
Functions of Operating System (Very Important — Frequently Asked)
| Function | Description |
|---|---|
| Memory Management | Allocating/deallocating RAM |
| Process Management | Managing multiple running programs |
| Device Management | Controlling input/output devices |
| File Management | Creating, deleting, organizing files/folders |
| Security Management | Password protection, user access control |
| User Interface | Provides CLI or GUI |
| Error Detection | Handles hardware/software errors |
Types of Operating System
| Type | Description | Example |
|---|---|---|
| Batch OS | Similar jobs are grouped and processed together; no direct user interaction | Old payroll systems |
| Time-Sharing OS | CPU time is divided among multiple users in turns | Multics |
| Distributed OS | Multiple computers work together as one system | — |
| Network OS | Designed for server-client environments | Windows Server, Novell NetWare |
| Real-Time OS (RTOS) | Gives response within a fixed time; no delay allowed | Air traffic control, Robotics |
| Multi-user OS | Multiple users can use it simultaneously | UNIX, Linux |
| Multitasking OS | One user can run multiple programs at once | Windows |
| Single-user OS | Only one user at a time | MS-DOS |
| Multiprocessing OS | Multiple CPUs work together | UNIX |
| Embedded OS | Built into small devices | Android (mobile), OS in ATMs/washing machines |
Types of User Interface
| Interface | Description | Example |
|---|---|---|
| CLI (Command Line Interface) | User types text commands to give instructions | MS-DOS, UNIX Shell |
| GUI (Graphical User Interface) | User interacts via icons, menus, and windows (mouse-based) | Windows, macOS |
Popular Operating Systems (Important for GK)
| OS | Developer | Type | Note |
|---|---|---|---|
| MS-DOS | Microsoft | CLI | 1981, first popular PC OS |
| Windows | Microsoft | GUI | Became popular from Windows 95 onward |
| UNIX | Bell Labs (AT&T) | CLI/Multi-user | 1969, one of the oldest multi-user OS |
| Linux | Linus Torvalds | Open Source | 1991, free and open source |
| macOS | Apple | GUI | Used in Apple computers |
| Android | Mobile OS | Based on the Linux kernel | |
| iOS | Apple | Mobile OS | Exclusive to Apple devices (iPhone) |
Important Fact: Linus Torvalds created the Linux Kernel in 1991. Linux is an open-source OS.
Important Fact: UNIX was created by Ken Thompson and Dennis Ritchie at Bell Labs (1969).
Booting Process (Important Term)
Booting = The process from switching on the computer to loading the OS.
| Type | Description |
|---|---|
| Cold Booting | Starting the computer from a completely powered-off state |
| Warm Booting | Restarting a computer that is already switched on (Ctrl+Alt+Del) |
BIOS (Basic Input Output System) — Stored in the motherboard’s ROM; checks hardware during booting via POST.
POST = Power On Self Test
Kernel
The Kernel is the core/heart of the OS. It manages direct communication between hardware and software — including memory, CPU, and devices.
Quick Revision Table (Most Asked Facts)
| Fact | Answer |
|---|---|
| First PC Operating System | MS-DOS |
| Example of Open Source OS | Linux |
| Examples of Mobile OS | Android, iOS |
| CLI-based OS | MS-DOS, UNIX |
| GUI-based OS | Windows, macOS |
| Example of Real-Time OS | Air traffic control system |
| Creator of Linux | Linus Torvalds (1991) |
| Creators of UNIX | Ken Thompson & Dennis Ritchie |
| Core part of OS | Kernel |
| Program that checks hardware at boot | BIOS |
| Power On Self Test | POST |
