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Operating Systems By Nanda Page
Operating System – Soul of Computer • Without the operating system, a computer is only devices connected together…. . • Operating system brings life to computer and get amazing tasks done!
Operating System Fundamentals 1. 2. 3. 4. 5. What is an OS Components of an OS Functions of an OS Types of OS Common Operating Systems
Operating System The operating system (OS) is software that controls the interaction between hardware and user software when the computer is switched on, OS will first load into the main memory
Operating System Objectives • Human- Machine communication • Convenience – Makes the computer more convenient to use • Efficiency – Allows computer system resources to be used in an efficient manner • System protection and Error Handling • Platform for user’s programs to execute • Ability to evolve
Elements of an OS • User Interface – The part of the OS that you interface with. • Kernel – The core of the OS. Interacts with the Basic Input Output System (at one end), and the User at the other end. • File Management System – Organizes and manages files.
Types of Software • System Software- Performs essential operation tasks – Operating system – Utility programs • A utility is a program that performs a task that is not typically handled by the operating system. • Some utilities enhance the operating system's functionality. – Data compression – Backup – Antivirus – Screen savers • Driver Programs (Device Driver) – small program that allows a specific input or output device to communicate with the rest of the computer system
Types of Software • Application Software - Performs specific tasks for users – Business application – Communications application – Multimedia application – Entertainment and educational software
Hierarchy of computer software
The operating system's tasks 1. Booting a Computer 2. User-interface 3. Running Programs 4. Managing Files 5. Memory Management 6. Scheduling Jobs 7. Managing Devices 8. Establishing Internet Connection 9. Controlling Network 10. Task Management
Computer’s Boot Sequence • All of the components in your computer, such as the CPU, the hard drive and the operating system, work together as a team. • Memory is also one of the most essential parts of this team. From the moment you turn your computer on until the time you shut it down, your CPU is constantly using memory. • When you turn on the computer, the electric signals make active the processor chip. The processor loads the instructions stored in ROM. These are the computer’s startup instructions called Firmware. It is the BIOS (Basic Input /Output System), which is automatically activated when’ computer is turned on and tests the computer hardware. This type of testing is called Power-On Self Testing (POST). • Once the POST has successfully completed, the software loaded in ROM will begin to activate the computer's disk drives. When the computer activates the hard disk drive, it finds the first piece of the operating system: the bootstrap loader.
OS in action. . • The computer loads the operating system (OS) from the hard drive into the system's RAM. The most important component of operating system is called the Kernel. • The Kernel is the core of an operating system; It performs various functions remaining inside the RAM, such as management Of memory, input/output devices, application programs etc. The Kernel is memory resident program of operating system. • Cold Boot • Warm Boot
User-interface • User interface means how the user interacts with the computer to perform various tasks. The hardware devices like keyboard, mouse and monitor etc. are used for interfacing. • click graphical objects on screen. • Command-line user interface • Graphical user interface. GUI lets you control the system by using a mouse. Applications designed to run under one operating system use similar interface elements.
Icons Program running in a window Desktop Window control buttons Start menu Start button Taskbar Dialog box
Running Programs The operating system also provides the interface between the programs and the user. Through program, the user accesses other computer resources such as printer, backing storages or another application programs. Actually, in program the built-in instructions known as “system calls” are used that request the services from the operating system. • Similarly, in data communication, information is sent and received via operating system.
File System The data and programs are stored permanently on the disk for future use. • A file is a collection of bytes of information treated as a single unit. • It is given a name to make it easy to find and use later. • The file system keeps track of where a file is actually resident on a disk. • A disk (hard disk, floppy, optical disk) is subdivided into directories or folders.
Managing Files • The operating system keeps track of all the folders and files and subfolders. • The operating system maintains a list of these folders and files in the starting area of disk called the FAT (File Allocation Table). The FAT is created when the new disk is formatted by Operating system. • The FAT area of disk contains the names of files, addresses of the disk where the data or contents of the respective files are stored.
Memory Management • • The memory unit has very important role for data processing. High-speed cache -- This is fast, relatively small amounts of memory that are available to the CPU through the fastest connections. Cache controllers predict which pieces of data the CPU will need next and pull it from main memory into high-speed cache to speed up system performance. Main memory -- RAM. Secondary memory – Permanent Storage Virtual RAM –Part of hard disc under the control of the operating system.
Hierarchy of Memory
Memory Management n n n The critical parts of the operating system are maintained in RAM as long as the computer is on. When you open an application, it is loaded into RAM. Only the critical parts of an application are loaded in the RAM to conserve its usage, and later when other pieces as needed they are loaded one by one. After an application is loaded, any files that are opened for use in that application are loaded into RAM. When you save a file and close the application, the file is written to the specified storage device, and then it and the application are removed from RAM. The processor takes data and program instructions from RAM during processing. system clears the memory area allocated to that program and its data.
Memory Storage and Management • When an operating system manages the computer's memory, there are two broad tasks to be accomplished: • Each process must have enough memory in which to execute, and it can not run into the memory space of another process. • The different types of memory in the system must be used properly so that each process can run most effectively.
Scheduling Jobs • A job is an activity or operation that a processor performs. It may be receiving data from input device, sending output to output device or loading data from disk into RAM etc. • The operating system determines the order in which the jobs are to be processed. Sometimes, the operating system processes jobs on a first-come first- served basis. • But in some situations, one user may have higher priority than the other users. In this case, the operating system has to adjust the schedule. • Sometimes, a device is busy in processing a job and another job is sent to that device. For example, three documents are sent to printer but the printer can print only one document at a time. In this case, the operating system places the other documents in buffers.
Configuring Devices The functions of devices attached with the computer are controlled by the special system software called device drivers. The device driver tells the operating system how to communicate with a device. • A driver helps the operating system communicate with the electrical signals from computer hardware.
Connecting to Internet • connection between your computer and the ISP (Internet Service Provider) Server. • Some operating systems also have builtin browser program used to access the information on Internet. The information downloaded from the Internet is managed by the operating system in RAM as well as in the disk.
Controlling Network • Some Operating systems are specially developed, for networking-network operating systems • A network operating system organizes and coordinates multiple users and makes it possible to access and share resources on network. • Creating and deleting user accounts • security features-Unauthorized access & data security • Resources on Network
Task Management • A task is an operation such as storing, printing or calculating etc. • you are downloading information from the Internet through browser, listening speech, printing a document through word processing program, entering data into a worksheet etc. • Some operating systems, such as Windows, enable programs to share information.
1 Information is clipped from one application (Excel) 2 Using the clipboard Viewer to examine the information Pasting the information into another application (Word. Pro) 3
Types of Operating Systems • Single-user, single task - one user can effectively do one thing at a time. The Palm OS for Palm handheld computers • Single-user, multi-tasking - most people use on their desktop and laptop computers. Microsoft's Windows and Apple's Mac OS platforms • Multi-user- Windows NT, Unix, VMS and mainframe operating systems, such as MVS, are examples of multiuser operating systems. • Batch Processing
Types of Operating Systems • Time sharing processing – Each user is given a time slice to interact with the CPU. – The size of the time slice will depend on the system. – Each user is served in sequence. • Real-time operating system (RTOS) - Real-time operating systems are used to control machinery, scientific instruments and industrial systems. An RTOS typically has very little user-interface capability, and no end-user utilities, since the system will be a "sealed box" when delivered for use. • immediate response is needed. – anti-missile defense system – airplane landing control system
Uniprogramming • Processor must wait for I/O instruction to complete before preceding
Batch processing • Jobs, together with input data, are fed into the system in a batch. • The jobs are then run one after another. • No job can be started until previous job is completed
Multi-tasking • to handle 2 or more programs at the same time from a single user ‘s perception – CPU can only perform one task at a time, however, it runs so fast that 2 or more jobs seem to execute at the same time
Multi-programming • 2 or more programs store in the main memory at the same time • when one job reeds to wait (e. g. I/O operation), CPU switch to another job to execute • when the first job finishes waiting, CPU will get back the first job to execute
Parallel Processing • use 2 or more CPUs to handle jobs • computer networking without multiprocessing with multiprocessing Job 4 Job 3 Job 4 time Job 3 Job 1 CPU 1 Job 2 CPU 2 time Job 2 Job 1 CPU 1
Common Operating system stand-alone operating systems or single user operating systems • DOS - It is a single user operating system used in microcomputers. It is a command line interface operating system. Microsoft Corporation developed it for IBM 8086 microprocessor computers. It was the most popular operating system in microcomputers before the Windows. • Mac OS - developed by Apple Corporation in 1984 for Macintosh. This operating system provides the GUI. It was one of first operating system that introduced the GUI. • Microsoft Windows introduced by Microsoft. It is most used and powerful GUI operating system.
Network Operating System A network operating system typically resides on a server and controls the devices or computers connected to the network. • • • Windows NT Server Windows 2000 Server UNIX Solaris Novell’s Netware
Embedded Operating System Different special electronic devices (or handheld computers) are also controlled by the operating systems that are stored into a ROM chip. . i) Windows CE designed for the use in wireless communication devices, smaller computer such as handheld computer, in-vehicle devices etc. Windows CE interface is similar to that of Windows operating system. This operating system also supports multitasking, Internet access, e-mails etc. Many application programs such as Microsoft Word, Microsoft Excel etc. that are developed for this operating system can be run with Windows CE. ii) Pocket PC 2002 developed by Microsoft and is used on a specific type of handheld computer called the pocket PC. It is similar to Windows XP operating system and is used to access Internet, listen to music, and watch a video and to create word processing and spreadsheet documents etc. Iii)Palm operating system Designed for PDA
• So next time when you start your computer and work on it , do not forget to appreciate the invisible performer…. • Enjoy !!! • Thank you!!!