operating system

Operating System Fundamentals

Mr. Gaurav MeenaMr. Gaurav MeenaAssistant Professor

Department of Computer Sciences

Central University of Rajasthan , Ajmer

Introduction and Concepts

Outline

What is an Operating System? Types of Computer Systems Simple Batch Systems Multi-programmed Batched Systems Time-Sharing Systems Personal-Computer Systems Parallel Systems Distributed Systems Real-Time Systems Handheld Systems

What is an Operating System?

A software that controls the hardware.

Processors, storage, input/output devices, communication devices and data.

A software that manages the hardware.

A software that acts as a resources allocator.

How Can We Define Operating System?

Operating System (OS) is a program that controls the execution of applicationprograms. It is also defined as being the mean through which controlling of allocation and usage of hardware resources and coordinating of all software activities within a computer is done.

Where Can an OS Fit?

Operating System Objectives Convenience: Makes the computer more convenient to use.

Ease of Communication: Between Computer and user through a friendly

user interface. Among system components.

Abstraction: Hardware-independent programming model.

Efficiency: Allows computer system resources to be used in

an efficient manner.

Operating System Objectives (cont’d)

Monitoring and Alerting: Monitors and alerts failures and problems.

Ability to Evolve: Permit effective development, testing, and introduction of

new system functions without interfering with the services. Protection:

A layer of security is to be added to ensure that a certain level of security is maintained to protect user’s data.

Increasing performance: Maximizing the throughput and Minimizing time needed to

execute command.

Services Provided by the Operating System Program development: Such as editors and

debuggers. Program execution:

Load program and data, initialize environment. Access to I/O devices:

Attempt to read from and write to the ports and units. Controlled access to data: Access protection. System access: User authentication.

Services Provided by the Operating System (cont’d) Error detection and response: In case of error occurring, an error message

should be displayed. Internal and external hardware errors: Memory error. Device failure.

Software errors: Arithmetic overflow. Access forbidden memory locations.

Services Provided by the Operating System (cont’d) Accounting: Collect statistics. Monitor performance. Is used to anticipate future enhancements? Is used for billing users?

Functions of an Operating System on a Network

1. Sharing H/W among users.2. Allowing users to share data.3. Preventing users from interfering with one

another.4. Scheduling resources among users.5. Organizing data for secure and rapid

access.6. Handling network communications.

Components of Computer System Input devices Processing devices (Central Processing Unit) Output devices Storage devices Applications software

Word Processing – Spreadsheet - Database System software

Operating System - Utilities Users, or end users, are the people in the computing environment

who need the output that computer systems produce. Programmers are the people whose job it is to write programs to

supply this information.

Layers of Computer System

Computer-System Operation I/O devices and the CPU can

execute concurrently. Each device controller is

responsible of a particular device type.

Each device controller has a local buffer (memory).

CPU moves data from/to main memory to/from local buffers I/O is from the device to local buffer of controller.

Storage-Device Hierarchy

Storage systems organized in hierarchy. Speed Cost Volatility

What is a Kernel?

Module Kernel is responsible for:

• Memory allocation.

• Garbage collection

• Object finalization

• Module termination

• Interfacing to the underlying operating system, and clock functions

Types of Computer Systems

Simple Batch Systems Multi-programmed Batched Systems Time-Sharing Systems Personal-Computer Systems Parallel Systems Distributed Systems Real-Time Systems Handheld systems

Simple Batch System

Runs only one job at a time.

Smoothed transition between jobs to get maximum utilization.

Programs/data submitted in groups or batches.

Multi-programmed Batch System

Uses job scheduling to increase resources utilization.

Stores more than one program in memory. Based on the fact that any one job rarely

utilizes all computer resources. When one job is waiting for an I/O, other can

use CPU and/or any other I/O.

Time Sharing System

Uses time sharing to switch between multiple jobs.

Interactive. Provides a low response time to users.

Developed to large numbers of simultaneously interactive users.

A program shares in time only if it exists in memory.

Personal System (Desktop)

Every user has his own memory, processors, and I/O devices.

Became possible after investing micro-processors.

Computing may be distributed to the sites rather than central place.

Data may be shared among users through networks.

Distributed System

Computers that communicate using a network: WAN (Wide area network) or LAN (Local area network), i.e. independent computers that works as a single system.

Client-Server: A client is a computer that needs service. A server is a S/W or a H/W that do a single service (Printing, graphics, DB, e-mail).

Peer-To-Peer: Decentralized computers provide services to peers.

Incremental growth.

Parallel System

A computer contains two or more CPUs that share a common bus.

A job Should be split to discrete (independent) small jobs.

Exponential speed up in computation needs exponential increase in the number of processors.

Real-time System

Often used as a control device in a dedicated application such as: a. Controlling scientific experiments, b. Medical imaging systems, c. Industrial control systems.

Well-defined fixed-time constraints. Real-time system may be either hard or soft

system

Real-time System (cont’d)

Hard real-time system: Secondary storage limited or absent Data stored in short term memory. Conflicts with time-sharing systems. Not supported by general purpose OS.

Soft real-time system: Useful in applications (multimedia, virtual reality). Require Advanced OS features.

Handheld Systems

Personal Digital Assistants (PDAs) Cellular telephones Issues: Limited memory Slow processors Small display screens

Computer Categories Computers are generally classified in one of four

categories: small, or “microcomputers”; medium-sized, or “midrange computers”; large, or “mainframecomputers”; and super-large, or “supercomputers.”An emerging new category is “mobile devices,” asdiscussed next.

In general, the larger the computer, the greater itsprocessing power. For example, big computers canprocess data at faster speeds and can perform morecomplicated types of processing than can smallcomputers. Big computers can also accommodatelarger, more powerful support devices. **

Computer Categories

Mobile devices

Microcomputers

Midrange computers

Mainframe computers

Supercomputers

Mobile DevicesA mobile device is loosely defined as a very small computing device based on a wireless phone or pager. Such devices usually offer limited Internet access in addition to their regular functions, such as placing phone calls and sending and receiving pages or messages.

Personal ComputersA technological breakthrough in the early 1970s

made it possible to produce an entire CPU on asingle silicon chip smaller than a dime. These“computers-on-a-chip,” or microprocessors, can bemass-produced at a very low cost.

Microprocessors also made it possible to build inexpensive computer systems small enough to fit on a desk or your lap. The small computers at the heart of these systems have come to be called microcomputers or personal computers (PCs).

Personal Computers, cont’d. Although most microcomputers designed for home or

business use are desktop computers, smaller PCs areavailable. Portable PCs include notebook, tablet,handheld, and pocket computers.

PCs designed for network use only are referred to as network computers or thin clients. PCs or devices designed for Internet access only are called Internet appliances.

Most PC users choose between two major computer platforms when they buy a computer—PC compatiblesand Macintosh computers. Often, people refer to PC-compatible computers as the Windows platform or as IBM-compatible PCs.

Personal Computers, cont’d.

PC compatible—a personal computer based on Intel microcomputer or compatible CPUs

Macintosh—a type of personal computer manufactured by Apple

Midrange ComputersMidrange computers (or minicomputers) are regarded asmedium-sized computers. Most of them fall betweenmicrocomputers and mainframes in their processingpower.

A small or medium-sizedcompany, for example, mayfind a microcomputer systemjust too small or too slow tohandle its currentvolume of work.

Mainframes Mainstay of almost all large organizations

Specialize in high-volume processing of business transactions

Mainframes often operate 24 hours a day, serving dozensof users on terminalsduring regular businesshours and processing big jobssuch as payroll and billing lateat night.

SupercomputersSome organizations, such as large scientific researchlaboratories, have extraordinary demands for processingpower.

To meet applications needs such as very fast speeds and extreme degrees of accuracy, a few vendors offer very powerful computers, called supercomputers.

Many supercomputers todayare created by linking togethermultiple PCs or microprocessorchips.

Computer Categories vs. Systems

Mobile devices: Handheld systems.

Microcomputers: Desktop systems.

Midrange computers: Desktop & Real-time systems.

Mainframe computers: Batch & Time-share (Hybrid systems).

Supercomputers: Parallel & distributed systems.