OPERATING SYSTEMS LECTURE:
Chapter 1 INTRODUCTION TO OPERATING SYSTEMS
* Elements of a computer system: Hardware, Software, Peopleware, Communication, Data,
* Types of Software: System software and application software
| Type | Description | Examples |
System software | Basic Software | * SW that manages and controls hw and application sw * usually called OS * includes utility programs/ service programs * language processors | OSDevice driversDisc compressionOptimization swScreen saversAnti virus swCompilers/ interpreters |
| Middleware | Sw that operates between OS and appcn sw | DbmsCommunication mgmt sysOperations m toolsSw development system |
Application ...view middle of the document...
* a security guard, it controls the access to the system and files. It prohibits unauthorized users access to the system. It also prevents user from accidentally or intentionally interfering with each other.
* a manager, it handles the efficient allocation of resources. A resource is any object that can be allocated within the system. Examples are processor use, input/output devices, files and memory (RAM). It performs the following tasks:
1) Monitors resources continuously
2) Enforces policies and decides which gets what, how much and when
3) Allocates the resources
4) De-allocates the resources
* As a traffic officer, it directs the passage of data through the CPU and guides the CPU when to look in memory, when to read or write on the data storage, when to display on screen the data or provide a hard copy using the printer.
* As an accountant, it monitors the users who logs-on to the system, what kinds of resources are utlized by each user, and what resources are requested by each user. In other words, it keeps track of how a file has been accessed, who accessed it, what file, and when it was accessed.
To illustrate, below are the steps performed by the operating system when the user saves the document she is doing:
1. The user issues a save command while using an application program such as word processor.
2. The word processing application signals the operating system that a document must be saved to a disk.
3. The operating system communicates the document to the disk device driver for saving.
4. The disk device driver controls the disk drive as it saves the document.
OPERATING SYSTEMS EVOLUTION
Below is a basic list of the different types of operating systems arranged according to the time it was introduced. Many other types may come about because of advances in technology and in practice; most of these types may overlap.
Generation | Type of OS | Description |
1st gen1945-1955 | none | * Programmers operated the machine themselves |
2nd gen1955-1965 | Batch Operating System | * A type of system developed for the earliest computers that used punched card or tape for input, which were entered in a “batch”. * Jobs are processed serially, without user interaction. * Efficiency of the system was measured in throughput ( the number of jobs completed in a given amount of time) and turn-around ( measured in hours or days) |
2nd gen1955-1965 | Single User Operating System | * An operating system controlled by one user at a time and deals with one set of input devices. * Handheld computers and personal computers maybe categorized for single user. * Examples are DOS, Palm OS, Windows CE, Inferno, Newton OS, Internet Tablet OS. |
3rd Gen | Multiuser Operating System | * Allows a single computer – often mainframe – to deal with simultaneous input, output, and processing request from many users. * Most difficult responsibility is to...