Flashcards
SCC 211 - Operating Systems concepts - Introduction
Cards in this deck (34)
- 1What is an operating system?A program that acts as an intermediary between a user of a computer
and the computer hardware. - 2What are the operating system goals?Execute user programs and make solving user problems easier
Make the computer system convenient to use
Use the computer hardware in an efficient manner - 3Define the computer systems structure?Hardware – provides basic computing resources
Operating system
Application programs
Users - 4Describe the importance of operating systems to users?Users want convenience, ease of use
Don’t care about resource utilization - 5Example of shared computers?mainframe or minicomputer must keep all
users happy. - 6Two different operating system definition?OS is a resource allocator
OS is a control program
-controls execution of programs to prevent errors. - 7What is the kernel?The kernel acts as a bridge between applications and the actual data processing done at the hardware level.
“The one program running at all times on the computer” - 8What does bootstrap program do?Initializes all aspects of system
Loads operating system kernel and starts execution - 9Where is bootstrap program loaded and stored?bootstrap program is loaded at power-up or reboot
Typically stored in ROM or EPROM, generally known as firmware - 10Can you summarise the Computer System operation?One or more CPUs, device controllers connect through common bus providing access to shared memory
Concurrent execution of CPUs and devices competing for memory cycles - 11Can you describe fully the stages of computer system operation? Each device controller is in charge of a particular device type
Each device controller has a localbuffer
CPU moves data from/to main memory to/from local buffers
I/O is from the device to local buffer of controller
Device controller informs CPU that it has finished its operation by causing an interrupt - 12How do IO devices and computers execute together?I/O devices and the CPU can execute concurrently
- 13Where does interrupts transfer control to and through what?Interrupt transfers control to the interrupt service routine generally,
through the interrupt vector, which contains the addresses of all the
service routines. - 14What should interrupt architecture do to interrupt instructions?Interrupt architecture must save the address of the interrupted
instruction - 15What happens to incoming interrupts as another interrupt is being processed?Incoming interrupts are disabled while another interrupt is being
processed to prevent a lost interrupt - 16What is a trap?A trap is a software-generated interrupt caused either by an error or a
user request - 17Is operating system interrupt driven?An operating system is interrupt driven.
- 18Describe the process of interrupt handling?The operating system preserves the state of the CPU by storing registers and the program counter
Determines which type of interrupt has occurred: polling or vectored interrupt system.
Separate segments of code determine what action should be taken for
each type of interrupt - 19What is a polled interrupt?a polled interrupt is a specific type of I/O interrupt that notifies the part of the computer containing the I/O interface that a device is ready to be handled.
The interrupt controller must poll (send a signal out to) each device to determine which one made the request. - 20What is a vectored interrupt?a vectored interrupt is an I/O interrupt that tells the part of the computer that handles I/O interrupts at the hardware level that a request for attention from an I/O device has been received and and also identifies the device that sent the request.
- 21Two different types of control mechanisms to users as to the implementation of I/O?After I/O starts, control returns to user program only upon I/O completion.
After I/O starts, control returns to user program without waiting for I/O completion. - 22What is a system call?a system call is the programmatic way in which a computer program requests a service from the kernel of the operating system it is executed on.
- 23What is a device status table and how is it used?Device-status table contains entry for each I/O device indicating its type, address, and state
Operating system indexes into I/O device table to determine device status and to modify table entry to include interrupt - 24What is direct memory access structure?Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system memory (RAM), independent of the central processing unit (CPU).
- 25Why is direct memory access structure used?Used for high-speed I/O devices able to transmit information at close
to memory speeds - 26What does the device controller do in direct memory access structure?Device controller transfers blocks of data from buffer storage directly to main memory without CPU intervention.
Only one interrupt is generated per block, rather than the one interrupt per byte. - 27Define two properties of Main Memory?Random access
Typically volatile - 28What is secondary storage?extension of main memory that provides large nonvolatile storage capacity.
- 29What are magnetic disks?Magnetic disks – rigid metal or glass platters covered with magnetic
recording material - 30What is the name given to the divided parts of a disk surface in a magnetic disk?Disk surface is logically divided into tracks, which are subdivided into sectors.
- 31What determines the interaction between a magnetic disk and the computer?The disk controller determines the logical interaction between the device and the computer.
- 32What is caching?Caching – copying information into faster storage system; main memory can be viewed as a cache for secondary storage.
- 33What attributes are storage systems weighed against?Speed
Cost
Volatility - 34What is caching?
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- Flashcards on SCC 211 - Operating Systems concepts - Introduction, created by Ayo Olutobi on 08/03/2017.
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- Ayo Olutobi
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