Chapter 1 - Introduction Flashcards
What the definition of an OS?
A program that acts as an intermediary between a user of a computer and the computer hardware
What are an OS’s three goals?
1) Execute user programs
2) Make computer system easy to use
3) Utilize hardware efficiently
What is the hierarchy of the computer system?
Hardware OS Applications Users
What are two aspects of an OS?
Resource Allocator and Control Program
What is a resource allocator?
Part of OS that decides between conflicting requests for efficient and fair resource use
What is a control program?
Part of OS that controls execution of programs to prevent errors and improper use of computer
What is a kernel?
The one program running at all times on the computer
What is a bootstrap program?
Program stored in ROM or EPROM that initializes all aspects of the system, loads OS kernel and starts execution
When is the bootstrap program loaded?
At power-up or reboot
Can I/O and CPU execute concurrently?
Yes
How do device controllers inform CPU that it is finished with an operation?
By causing an interrupt
What does an interrupt do?
Transfers control of CPU to the Interrupt Service Routine through the Interrupt Vector
What is the interrupt service routine?
Contains addresses of all the service routines
What happens to incoming interrupts when another is already being processed?
Incoming interrupts are disabled
What is a trap?
A software generated interrupt caused by error or user request
How does the OS determine what kind of interrupt has occurred?
Through polling or the vectored interrupt system
What is a system call?
How a program requests a service from the OS kernel
What is the Device-status table?
Table that contains entry for each I/O device indicating its type, address, and state
Why would the OS index into the I/O device-status table?
To determine device status and to modify table entry to include interrupt
What is main memory?
Random access, volatile memory, aka RAM
What is hierarchy of the storage structure?
1) Registers
2) Cache
3) Main memory (RAM)
4) Electronic Disk (SSD)
5) Magnetic Disk (HD)
6) Optical Disk (CDs)
7) Magnetic Tape
What is secondary storage?
Extension of main memory that provides large non-volatile storage
What does the disk controller do?
Determines logical interaction between the disk and the computer
What is caching?
Copying information into faster storage system
What are the advantages of Multiprocessor Systems?
Increased throughput and reliability, economy of scale
What is a clustered system?
Collection of linked multiprocessor systems
What is multiprogramming?
Having the OS switch to another job when it needs to wait (ex: for I/O), aka job scheduling
What is timesharing?
When CPU switches jobs so frequently that each user can interact with each job while it is running, aka interactive computing
What is dual-mode and what does it do?
Having a user mode and kernel mode, which allows OS to protect itself and other system components
What does it mean to be privileged?
To be able to execute in kernel mode
What is the difference between a single-threaded and multi-threaded process?
Single-threaded process have one Program Counter (PC) while multi-threaded have one for each thread
What is protection?
Mechanism for controlling access of processes or users to resources defined by the OS
What is security?
Defense of a system against attacks
What do Users IDs (UID) and Group IDs (GID) do?
Determine which users and groups of users have which privileges
