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Review: CS100: Introduction to Computer Science n Arithmetic/Logic Operations Logic: AND, OR, XOR q n q Lecture 8: Operating System n Communicating with other devices Controller, q n n Chapter 3: Operating Systems n 3.1 The History of Operating Systems n 3.2 Operating System Architecture n 3.3 Coordinating the Machine’s Activities n An operating system: the software that controls the overall operation of a computer. q q q Operating Systems UNIX q Originally developed by AT&T in 1960s Popular in large computer systems. DOS q 1981—1997 by IBM q Used PCs Windows (1985 -- now) q By Microsoft, q Add Graphical User interface to DOS systems q Wildly used in PCs LINUX (1980s – now) q UNIX-like operating systems q A free software., source code is available for anyone to use and modify n n Provides the means for a user to store and retrieve files Provides the interface for a user to request the execution of a program Coordinates the execution of programs … Evolution of Shared Computing n q n Specialized controllers for each type of device General purpose controllers: USB, FireWire Functions of Operating Systems q n Masking Rotate and Shift: circular shift, logical shift, arithmetic shift Arithmetic: add, subtract, multiply, divide q n Batch processing q Collecting jobs in a single batch and then execute them without further interaction with the user. Interactive processing q Allows a program being executed to carry on a dialogue with the user through remote terminals q n Requires real-time processing Time-sharing/Multitasking n n n n More tasks being performed at the “same time” or serve more users at the “same time” Time-sharing system: divide time into intervals, jobs takes turns to use CPU time. Provide reasonable real-time processing for each user. Multiprocessor machines q Assign different tasks to different processors 1 Figure 3.1 Batch processing Types of Software n q Performs specific tasks for users Database systems, games, program developing software, etc. System software q q q Provides infrastructure for application software Consists of operating system and utility software Utility software: programs for performing fundamental activities, but not included in operating systems. n E.g data compression software, network communication software. Operating System Components n Figure 3.3 Software classification Application software q n Figure 3.2 Interactive processing Shell: interface between users and the internal part (kernel)of operating systems. q q Figure 3.4 The shell as an interface between users and the operating system Text based Graphical user interface (GUI) n Window manager: allocates block of space on the screen, keeps track of which application is associated with each window. n Kernel: Performing basic required functions n Allows different shells to access the same kernel 2 Operating System Components n n Shell: interface between users and the internal part of operating systems. Kernel: Performing basic required functions q q q q File manager Device drivers Memory manager Scheduler and dispatcher File Manager n Coordinates the use of mass storage devices q Maintain records of all files n q n Directory (or Folder): A user-created bundle of files and other directories (subdirectories) n Directory Path: A sequence of directories within directories n n Device Drivers n n Software units that communicate with the controllers to carry out operations on the peripheral devices. n Allocates space in main memory n May create the illusion that the machine has more memory than it actually does (virtual memory) by playing a “shell game” in which blocks of data (pages) are shifted back and forth between main memory and mass storage Each device driver is uniquely designed for its particular type of device and translate the generic requests to more technical steps required by the device q 512MB main memory, 1024MB virtual memory n n Printer drive, disk drive Scheduler and Dispatcher: Processes n n Process: The activity of executing a program Process State: Current status of the activity q q q n Value in program counter: the current position in the program being executed Values in general purpose registers: Associated memory cells Process Table: store information of processes q Memory area assigned to a process q q The priority of the process Whether the process is ready or waiting courses/cs100/slides on UNIX courses\cs100\slides on WINDOWS Memory Manager n n Where a file is stored, which users are allowed to access it Records are kept on the individual storage medium containing the related files. n Reserve 1024MB on a magnetic disk and store bit patterns there. Data are divided into pages. Transfer pages into main memory if information are needed soon. Transfer pages back into the disk if information will not be needed in short time. Process Administration n Scheduler: Adds new processes to the process table and removes completed processes from the process table n Dispatcher: Controls the allocation of time slices to the processes in the process table q The end of a time slice is signaled by an interrupt. q 3 Figure 3.6 Time-sharing between process A and process B How Does An Operating System Get Started (Bootstrapping/booting) n ROM: read-only memory q q n Bootstrap: the program stored in ROM q q q q Figure 3.5 The booting process A portion of main memory but constructed from non-volatile memory cells. Its contents can be read but not altered. Run by the CPU when power is turned on Transfers operating system from mass storage to main memory Executes jump to operating system The operating system then takes over and begins controlling the machine’s activity. Questions: n List the components of a typical operating system and explain the role of each. n Summarize the booting procedure. n What is the difference between a process and a program? Announcements: n Next lecture: Review Session n Monday, March 5th : first in-class exam 4