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What are the three main functions of an operating system?
- Manage the computer hardware
- Support application software
- Establish a user interface
*List and describe the three main tasks involved in the operating system managing computer hardware.
- CPU performance and utilization
- Memory allocation and protection
- Input-output management
List some types of application software that is supported by operating systems.
- Word processors
- Electronic spreadsheets
- Database management
- Computer graphics and games
*What are two types of user interfaces?
- Textual, with a command line prompt
- Graphical, with windows, menus and icons
List and describe four different approaches to processing.
- 1) Batch processing - non-interactive execution of one or more programs with distinct input and output sessions
- 2) Time-sharing - Multiple programs executing "simultaneously" via time slices on a single computer (either many users on one computer or one user multitasking)
- 3) Interactive processing - Execution of a program with additional input from the user and output to the user during execution.
- 4) Multiprocessing - Multiple CPUs available within the computer system, either across a network or within a single machine (e.g., a supercomputer)
*(CPU Management) List the five states of a process that is being executed by the CPU and describe the transition between the current state and the next state.
- 1)New process (file, not loaded yet) - OS "admits" process
- 2)Ready process (loaded into RAM) - OS "dispatches" process -> Running process
- 3)Waiting process (needs I/O or some event in memory, temporarily can't run) - OS moves process to Ready state when ready again
- 4)Running process (in RAM, with CPU processing its instructions) - OS starts cleaning up after finished
- 5)Terminated process (finished executing, must mark its memory as free)
Describe three common scheduling options for OS scheduling CPU.
- 1) First-come first-served - obvious. Disadvantage: smaller jobs may have to wait an inordinate amount of time.
- 2) Shortest job first - obvious. Disadvantage: large jobs must wait until everything else is finished before starting.
- 3) Round Robin - time slices. Processes constantly interrupted when their slices expire.
List and describe two common resource allocation problems.
- 1) Mutual exclusion - when two processes require access to the same nonshareable resource at the same time they cannot both be accomodated. (e.g. - producer / consumer)
- 2) Deadlock - when two processes are simultaneously blocking each other's progress then neither may be able to proceed. (e.g. - flash drive & DVD)
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