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CS100: Introduction to Computer Science

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