7SYSTEM SOFTWARERefers to the Operating system and all utility programs that manage computer resources at a low level.It includes compilers, loaders, linkers and debuggers.
8APPLICATION PROGRAMS A program or group of programs designed for end users.Examples: Word processing, Graphics,Spreadsheets, Databases,Games.
9GOALS OF AN OPERATING SYSTEM To make the computer system convenient to use.To use the computer hardware in an efficient manner.
10PURPOSE OF AN OPERATING SYSTEM The purpose of an operating system is to provide an environment in which a user may execute programs.
11WHAT IS AN OPERATING SYSTEM? An Operating System is an interface between user and hardware of a computer system.The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.Operating systems can be classified as follows:multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.multiprocessing : Supports running a program on more than one CPU.multitasking : Allows more than one program to run concurrently.multithreading : Allows different parts of a single program to run concurrently.real-time real_time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.As a user, you normally interact with the operating system through a set of commands. For example, the DOS operating system contains commands such as COPY and RENAME for copying files and changing the names of files, respectively. The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen.
12WHAT IS AN OPERATING SYSTEM? An Operating System is a system software which may be viewed as an organized collection of software consisting of procedures for operating a computer and providing an environment for execution of programs.
13OTHER DEFINITIONS An Operating System is a control program. An Operating System is similar to a Government.An Operating System can be defined as a Resource Manager.
14OTHER DEFINITIONSAn Operating System is the layer between the H/W and the S/WAn Operating System is a virtual computer managerOperating System is the first program run on a computer when the computer boots up
15USER INTERFACE A set of commands or menus through which user communicates with theprogram.
16TYPES OF INTERFACES Command driven Menu driven Graphical user interface(GUI)The junction between a user and a computer program. An interface is a set of commands or menus through which a user communicates with a program. A command-driven interface is one in which you enter commands. A menu-driven interface is one in which you select command choices from various menus displayed on the screen.The user interface is one of the most important parts of any program because it determines how easily you can make the program do what you want. A powerful program with a poorly designed user interface has little value. Graphical user interfaces (GUIs) that use windows, icons, and pop-up menus have become standard on personal computers.
17WAYS TO INTERACT WITH OPERATING SYSTEM OPERATING SYSTEM CALLSOPERATING SYSTEM COMMANDSPrograms rely on facilities provided by the o/s to gain access to computer system resources. There are two ways one can interact with o/s namely, system calls and system commands.
18OPERATING SYSTEM COMMANDS SYSTEM CALLSSystem Calls provide the interface to arunning program and the O/S.OPERATING SYSTEM COMMANDSUsers nay interact with the O/S directlyby means of O/S commands.User program receives o/s services through the set of system calls. The following system calls will be generated by the o/s:Prompt messages for inputting file names and reading it from terminal.Open source and destination filePrompt error messages.Read the source file.Write into the destination file.Sysem commands can be given directly. For example to display directories in MSDOS we give the command “dir”
19MULTIPROGRAMMINGMultiprogramming was used as a technique to enhance the throughput efficiency.Overlapping interleaving computing of different jobs.More than one job is “ready” at the same time.The ability to execute more than one task at the same time, a task being a program. The terms multitasking and multiprocessing are often used interchangeably, although multiprocessing sometimes implies that more than one CPU is involved.In multitasking, only one CPU is involved, but it switches from one program to another so quickly that it gives the appearance of executing all of the programs at the same time.There are two basic types of multitasking: preemptive and cooperative. In preemptive multitasking, the operating system parcels out CPU time slices to each program. In cooperative multitasking, each program can control the CPU for as long as it needs it. If a program is not using the CPU, however, it can allow another program to use it temporarily. OS/2, Windows 95, Windows NT, the Amiga operating system and UNIX use preemptive multitasking, whereas Microsoft Windows 3.x and the MultiFinder (for Macintosh computers) use cooperative multitasking.
20Different types of Multiprogramming Operating System Multitasking operating systemMultiprocessing operating systemMulti-user operating systemOperating systems can be classified as follows:multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.multiprocessing : Supports running a program on more than one CPU.multitasking : Allows more than one program to run concurrently.multithreading : Allows different parts of a single program to run concurrently.real-time real_time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.
21FUNCTIONS OF OPERATING SYSTEM Memory managementProcess managementDevice managementInformation managementProtectionError Handling
22FUNCTIONS OF OPERATING SYSTEM Memory managementProcess managementThe o/s keeps track ofthe memory, what parts arein use and by whom.Device managementInformation managementMemory management is primarily concerned with allocation of main memory of united capacity to requesting processes.Two important features of memory management function are protection and sharing.ProtectionError Handling
23FUNCTIONS OF OPERATING SYSTEM Memory managementProcess managementDevice managementThe o/s keeps track ofprocessors and the statusof processes. It decideswho will have a chance touse the processor.Information managementProcess management is concerned with the management of physical processors(CPU’s) I.e., allocation of processes to a processor. A process is a program under execution.ProtectionError Handling
24FUNCTIONS OF OPERATING SYSTEM Memory managementProcess managementDevice managementInformation managementThe o/s keeps track of the devices,channels, control units anddecides what is an efficientway to allocate the device.ProtectionError Handling
25FUNCTIONS OF OPERATING SYSTEM O/S keeps track of the information,its location, use, status etc.and decides who gets useof the resources,enforce protection requirements.Memory managementProcess managementDevice managementInformation managementFile management is one of the most visible services of an operating system.File management deals with the management of data program which reside on secondary storage device. File mapping is done by file management.File management includes:1.Mapping of logical file address to physical disk address.2.Management of disk space and allocation and dellocation3.Keeping track of all files in the system.4.Support for protection and sharing of files recoveryl.ProtectionError Handling
26FUNCTIONS OF OPERATING SYSTEM An o/s is to protect the userfrom unauthorized accessof his files or data.And also it should protectitself from usersMemory managementProcess managementDevice managementInformation managementProtectionError Handling
27FUNCTIONS OF OPERATING SYSTEM An o/s must respond toerrors by taking theappropriate actions.Memory managementProcess managementDevice managementInformation managementProtectionError Handling
28FILE CONCEPT File is a collection of related information. It is named and is referred by its name.Files are organized into directories foreasy access.These are commonly store on secondary storage devices. File mapping is done by file management. File often appears as as sequence of bits,bytes, lines or records whose meaning is defined by programmer.
30CLIENT-SERVER MODEL User process(client process) sends the request to a server process, whichwhen does the work and sends backthe answer.
31CLIENT-SERVER ARCHITECTURE CLIENT is an application that runs on apersonal computer or on a workstationand relies on SERVER to perform someoperations such as managing files,disk drives, printers or network traffic.
32NETWORK OPERATING SYSTEM The Software that enhances a basicOperating System by adding NetworkingFeatures.Examples: Novell Netware, WINDOWS NT
33Operating system is an essential component of system software which consists of procedures for managing computer resources.Operating system functions primarily includes Memory, Process,Device, File management.