Computer System Software

Topic: Computer System Software

Class: SSS One

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Definition of Software

Computer software is the logical, non-physical component of a computer system.

1. Software is a program that enables a computer to perform a specific task, as opposed to the physical component of the system (hardware).
2. It is a set of instructions and procedures passed to the computer to perform certain activities or tasks.
3. It can also be defined as a set of instructions that direct the activities of the computer system to undertake a specific task.

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Types of Computer Software

Software is broadly divided into two main groups:

1. System Software (Focus of this lesson)
2. Application Software (Designed for specific user tasks, like Word or games)

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Definition of System Software

• System software is a collection of programs designed to operate, control and extend the capabilities of the computer.
• It controls the way the different computer components communicate with one another.
• It acts as the interface between the hardware and the application software.

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Types of System Software

The major types of system software are:

1. Operating System
2. Translators (Assemblers, Compilers, Interpreters)
3. Utility Programs (or tools)

Operating System (OS)

The OS is the most important program that runs on a computer. It manages the hardware and software resources and provides common services for programs.

Examples of Operating Systems

• Mac (Macintosh)
• Windows
• Linux
• UNIX
• DOS
• Android
• iOS, etc.

Core Components of the Operating System

The operating system is structured internally into several modules, with the core component being the kernel.

The Kernel

The kernel is the core of the operating system. It is the first program loaded when the computer starts and remains in memory until shutdown.

Primary Functions: Managing hardware resources (CPU, memory, devices), and handling system calls.

System Calls

System calls are the mechanism by which a program requests a service from the kernel (e.g., requesting memory, writing to a file, or reading input).

Shell / User Interface

The shell (or User Interface, UI) is the layer of the OS that processes user commands, translating them into actions for the kernel. It can be GUI or CLI.

File Management System

Responsible for organizing, storing, and retrieving files and managing access to data on storage devices.

Functions of the Operating System

• Memory Management
• Process Scheduling
• File Management
• Device Management
• User Interface
• Security/Resource Accounting
• Bootstrapping

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Types of Operating Systems

1. Real-Time Operating System (RTOS): A Real-Time Operating System, commonly known as an RTOS, is a software component that rapidly switches between tasks, giving the impression that multiple programs are being executed simultaneously on a single processing core.
   Examples: VxWorks, QNX, eCos, RTLinux
2. Single-User, Single-Task: As the name implies, this type of operating system is designed to manage the computer so that one user can perform only one task at a time.
   Examples: Palm OS, Pocket PC, MS-DOS
3. Single-User, Multi-Tasking: As the name implies, this type of operating system is designed to manage the computer so that one user can effectively perform more than one task at a time.
   Examples: Windows Family, macOS, Linux
4. Multi-User: A multi-user operating system allows multiple users to access and utilize the computer’s resources simultaneously.
   Examples: UNIX, Novell NetWare, Windows Server
5. Distributed: A distributed operating system manages a group of independent computers and makes them appear to function as a single system.
   Examples: Solaris, AIX, Mach/OS
6. Embedded: Embedded operating systems are designed to be used in handheld or dedicated computer systems.
   Examples:
   • Symbian
   • Embedded Linux (Android is a subset)
   • BlackBerry OS (for BlackBerry phones)
   • iOS (a subset of macOS, used in Apple’s mobile devices)
   • Palm OS

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User Interfaces (UI)

The UI is the part of an operating system that allows users to interact with the computer.

1. Graphical User Interface (GUI):

   Users interact via icons and menus using a mouse. Examples: Mac, Windows.

2. Text User Interface (TUI) / Command Line Interface (CLI):

   Users type commands via the keyboard. Examples: DOS, Unix (e.g., “C:/>”).

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Translators

Translators convert programs written in various languages (source code) into machine code (object code) for CPU execution.

Comparison of Translators

Translator	Input Language	Action	Key Feature
Assembler	Assembly Language	Translates the whole program.	Translates mnemonics into machine code.
Compiler	High-Level Language	Translates the entire program at once.	Faster execution; produces executable files.
Interpreter	High-Level Language	Translates and executes one statement at a time.	Easier debugging but slower execution.

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Utility Programs

Utility software (or service program) is computer software designed to help analyze, configure, optimize, or maintain the computer system.

Examples of Utility Programs

• Anti-virus: Prevents and removes malware or spyware.
• Backup Utilities: Creates copies of files for data recovery.
• Data Compression Utilities: Reduces file sizes (e.g., WinZip, WinRAR).
• File Managers: Helps manage files (copy, rename, delete).
• Disk Cleaners: Removes unnecessary files to free space.
• Disk Partitioners: Divides one drive into multiple logical drives.
• Cryptographic Utilities: Encrypts or decrypts data for security.

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🧠 Test Your Knowledge

1. Which type of software is responsible for managing the computer's memory, processes, and files?

Application Software
Utility Program
Operating System
Translator

2. A program that translates the entire high-level language source code into machine code before execution is called a(n):

Interpreter
Assembler
Compiler
Utility Program

3. Which function is NOT a primary responsibility of the Operating System?

Managing peripheral devices.
Running a word processor application.
Scheduling CPU time for processes.
Providing a user interface.

4. Which type of user interface requires the user to type in commands (e.g., in DOS)?

GUI
TUI / CLI
RTOS
Multi-tasking

5. Anti-virus software is an example of a:

Translator
Multi-user OS
Utility Program
Application Software