Operating System Concepts

What is an Operating System?

• An Operating System (OS) is a software interface between computer hardware and the user.

• Every computer needs at least one OS to run other programs.

• Applications like browsers, MS Office, and games require an environment provided by the OS to run.

• The OS facilitates communication with the computer without needing to know the computer's language.

• Computers and mobile devices cannot be used without an OS.

History of OS

• Operating systems were first developed in the late 1950s to manage tape storage.

• The General Motors Research Lab implemented the first OS in the early 1950s for their IBM 701.

• In the mid-1960s, operating systems began using disks.

• The first version of the Unix OS was developed in the late 1960s.

• Microsoft's first OS was DOS, built in 1981 by purchasing 86-DOS software.

• Windows first appeared in 1985 as a GUI paired with MS-DOS.

Examples of Operating Systems with Market Share

• Windows: 40.34%

• Android: 37.95%

• iOS: 15.44%

• Mac OS: 4.34%

• Linux: 0.95%

• Chrome OS: 0.14%

• Windows Phone OS: 0.06%

Types of Operating Systems

• Batch Operating System:

  • Processes similar jobs together to speed up processing.

  • Users do not directly interact with the computer; jobs are submitted offline (e.g., via punch cards).

• Multitasking/Time-Sharing Operating Systems:

  • Allows multiple users at different terminals to use a single computer system simultaneously.

  • Processor time (CPU) is shared among multiple users, known as time sharing.

• Real-Time Operating Systems:

  • Processes and responds to inputs in a very small time interval.

  • Examples: Military software systems, space software systems.

• Distributed Operating Systems:

  • Uses multiple processors located in different machines to provide fast computation.

• Network Operating Systems:

  • Runs on a server and manages data, users, groups, security, applications, and other networking functions.

• Mobile Operating Systems:

  • Designed to power smartphones, tablets, and wearable devices.

  • Examples: Android, iOS, BlackBerry, Web, and watchOS.

Functions of Operating Systems

• Managing memory, files, processes, I/O system & devices, security, etc.

Detailed Functions:

1. Process Management

• Creates and deletes processes.

• Provides mechanisms for synchronization and communication among processes.

2. Memory Management

• Allocates and de-allocates memory space to programs.

3. File Management

• Manages file-related activities: organization, storage, retrieval, naming, sharing, and protection of files.

4. Device Management

• Keeps track of all devices through the I/O controller.

• Allocates and de-allocates devices.

5. I/O System Management

• Hides the peculiarities of hardware devices from the user.

6. Secondary-Storage Management

• Manages primary storage, secondary storage, and cache storage.

• Instructions and data must be stored in primary storage or cache for running programs.

7. Security

• Protects data and information against malware and unauthorized access.

8. Command Interpretation

• Interprets commands given by the user and allocates system resources.

9. Networking

• Enables communication between processors that do not share memory, hardware devices, or a clock, through a network.

10. Job Accounting

• Tracks time and resources used by various jobs and users.

11. Communication Management

• Coordinates and assigns compilers, interpreters, and other software resources to various users.

Features of Operating Systems

• Protected and supervisor mode

• Allows disk access and file systems

• Device drivers

• Networking

• Security

• Program Execution

• Memory management

• Virtual Memory

• Multitasking

• Handling I/O operations

• Manipulation of the file system

• Error Detection and handling

• Resource allocation

• Information and Resource Protection

Advantages of Using Operating Systems

• Hides hardware details by creating an abstraction.

• Easy to use with a GUI.

• Provides an environment to execute programs/applications.

• Makes the computer system convenient to use.

• Acts as an intermediary between applications and hardware.

• Provides computer system resources in an easy-to-use format.

• Acts as an intermediator between all hardware and software of the system.

Disadvantages of Using Operating Systems

• Issues in the OS can lead to data loss.

• OS software can be expensive for small organizations.

• Operating systems are never entirely secure and are always vulnerable to threats.

What is the Kernel?

• The kernel is the central component of an operating system.

• It manages communication between software and hardware.

• It is the nucleus of a computer, making hardware and software communication possible.

• The kernel is the innermost part of an OS, while the shell is the outermost part.

Features of the Kernel

• Low-level scheduling of processes

• Inter-process communication

• Process synchronization

• Context switching

Types of Kernels

1. Monolithic

• A single block of code that provides all OS services.

• Simplistic design with a distinct communication layer between hardware and software.

2. Microkernels

• Manages system resources where services are implemented in different address spaces.

• User services are stored in user address space, and kernel services are stored under kernel address space.

• Reduces the size of both the kernel and the operating system.

Difference Between Firmware and Operating System

Difference Between 32-Bit vs. 64-Bit Operating Systems

Summary

• An operating system acts as an interface between the user and computer hardware.

• Different types of OS include Batch, Multitasking/Time Sharing, Multiprocessing, Real Time, Distributed, Network & Mobile OS.

• Operating systems were first developed in the late 1950s to manage tape storage.

• The OS works as an intermediary, helping users communicate with the computer.

• The kernel is the central component, managing communication between hardware and software.

• Two popular kernel types are Monolithic and Microkernels.

• Key functions include Process, Device, File, I/O, Secondary-Storage, and Memory management.