Lecture 1: Introduction to Operating Systems

Operating System

A program that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware.

Operating System

A software that manages a computer's hardware

operating system

is the one program running at all times on the computer (usually called kernel), with all else being application programs;

Kernel

The most important part of the operating system. It is the primary interface between the hardware and the processes of a computer.

Components of a computer system

- Hardware

- Application Programs

- Operating System

- Users

Hardware

The central processing unit (CPU), the memory, and the I/O devices provides the basic computing resources for the system.

Application Programs

Word processors, compilers, web browsers define the ways in which these resources are used to solve users' computing problems.

Operating System

Controls the hardware and coordinates its use among the various application programs for the various users.

Users

Users of a computer system.

Abstract view of the components of a computer system.

users

application programs

operating system

computer hardware

Computer System Organization

Typically, operating systems have a device driver for each device controller.

Device driver

This _____ understands the device controller and provides the rest of the operating system with a uniform interface to the device.

General-purpose computers

run most of their programs from rewritable memory, called main memory (also called RAM or Random-Access Memory).

Main Memory

It is a flexible and volatile type of storage device.

Main Memory

It is commonly implemented in a semiconductor technology called DRAM (Dynamic Random-Access Memory).

Bytes

All forms of memory provide an array of _______. Each ______ has its own address.

Load instruction

Moves a byte or word from main memory to an internal register within the CPU.

Store instruction

Moves the content of a register to main memory.

Storage-device hierarchy

registers

cache

main memory

nonvolatile memory

hard-disk drives

optical disk

magnetic tapes

Resource Manager

An operating system is a ______.

Resources that the operating system must manage

The system's CPU, memory space, file-storage, and I/O devices are among the resources that the operating system must manage.

Resource Management in OS

1. Process Management

2. Memory Management

3. File-System Management

4. Mass-Storage Management

5. Cache Management

6. I/O System Management

Process

A program in execution.

Process

- a program such as compiler is a process

- a word-processing program being run by an individual user on a PC is a process

resources

A process needs certain _______ --- it includes CPU time, memory, files, and I/O devices --- to accomplish its task.

These are typically allocated to the process while it is running.

initialization data

In addition to the physical and logical resources that a process obtains when it is created, various _______ (input) may be passed along.

passive entity, active entity

A program is a __________, like the contents of a file stored on disk, whereas a process is an ____________.

sequential

The execution of such a process must be _______.

The CPU executes one instruction of the process after another, until the process completes.

Process

It is the unit of work in a system. A system consists of collection of processes, some of which are operating-system processes and the rest of which are user processes.

The operating system is responsible for the following activities in connection with process management:

1. Creating and deleting both user and system processes;

2. Scheduling processes and threads on the CPUs;

3. Suspending and resuming processes;

4. Providing mechanisms for process synchronization;

5. Providing mechanisms for process communication;

Main Memory

Central to the operation of modern computer system.

Main Memory

A repository of quickly accessible data shared by CPU and I/O devices.

Main Memory

Generally the only large storage device that the CPU is able to address and access directly.

For example, for the CPU to process data from disk, those data must first be transferred to main memory by CPU-generated I/O calls. These instructions must be in memory for the CPU to execute them.

Memory Management

To improve both utilization of the CPU and the speed of the computer's response to its users, general-purpose computers must keep several programs in memory, creating a need for ________.

The operating system is responsible for the following activities in connection with memory management:

1. Keeping track of which parts of memory are currently being used and which process is using them;

2. Allocating and de-allocating memory space as needed; and

3. Deciding which processes and data to move into and out of memory.

File Management

One of the most visible components of an operating system.

secondary storage, tertiary storage

Physical media such as ______ is the most common, but ______ is also possible.

File

A collection of related information defined by its creator.

files

Commonly, _____ represent programs (both source and object forms) and data.

Data files

may be numeric, alphabetic, alphanumeric or binary.

Files

may be free-form like text files or formatted rigidly such as mp4 file format.

The operating system is responsible for the following activities in connection with file management:

1. Creating and Deleting Files;

2. Creating and Deleting directories to organize files;

3. Supporting primitive for manipulating files and directories;

4. Mapping files onto mass storage; and

5. Backing up files on stable (non-volatile) storage media.

HDDs and NVM devices

Most modern computer systems use _______ as the principal on-line storage media for both programs and data.

Most programs --- including compilers, web browsers, word processors, and games --- are stored on these devices until loaded into memory.

Secondary Storage

Since _____ is used frequently and extensively, it must be used efficiently.

The operating system is responsible for the following activities in connection with secondary storage management:

1. Mounting and un-mounting;

2. Free-space management;

3. Storage allocation;

4. Disk scheduling;

5. Partitioning; and

6. Protection

Caching

An important principle of computer systems. Information is normally kept in some storage system (such as main memory).

Cache

As it is used, it is copied into a faster storage system --- on a temporary basis.

caches, cache management

Because _____ have limited size, _______ is an important design problem.

Operating System

One of the purposes of an ________ is to hide the peculiarities of specific hardware devices from the user.

For example, in UNIX, the peculiarities of I/O devices are hidden from the bulk of the operating system itself by the I/O subsystem.

The I/O subsystem consists of several components:

1. A memory-management component that includes buffering, caching, and spooling;

2. A general device-driver interface; and

3. Drivers for specific hardware devices.

Types of Operating Systems

1. Batch Operating System

2. Multiprogramming Operating Systems

3. Multiprocessing Operating System

4. Multitasking Operating System

5. Time-Sharing Operating System

6. Distributed Operating System

7. Network Operating System

8. Real-time Operating System

Batch Operating System

This type of operating system does not interact with the computer directly.

An operator is present which takes similar jobs having the same requirement and groups them into batches.

Multiprogramming Operating Systems

can be illustrated as more than one program is present in the main memory and any of them can be kept in execution.

As a result, various jobs may share CPU time.

Multiprocessing Operating System

A type of operating system in which more than one CPU is used for the execution resources.

Multitasking Operating System

Simply a multiprogramming operating system with having facility of a Round-Robin Scheduling Algorithm.

It can run multiple programs simultaneously.

Time-Sharing Operating System

Each task is given some time to execute so that all the tasks work smoothly.

Each user gets the time of the CPU as they use a single system.

The task can be from a single user or different users.

Distributed Operating System

It use many central processors to serve multiple real-time applications and users.

Independent systems process their own memory unit and CPU.

Network Operating System

These systems run on a server and provide the capability to manage data, users, groups, security, applications, and other networking functions.

These types of operating systems allow shared access to files, printers, security, applications, and other networking functions over a small private network.

Real-time Operating System

These types of OS serve real-time systems.

Real-time systems are used when there are time requirements that are very strict like missile systems, air traffic control systems, robots, etc.