Operating Systems (General) Flashcards
OS between what?
Hardware and Applications/System Programs
What is the 2 views and what is important for each? (3; 2 (2nd : 2))
User View:
1) Ease of use
2) Efficiency
3) Resource Utilization
System View:
1) Resource allocator: OS must decide how to allocate resources (CPU, Memory, File storage, IO devices etc.) to specific programs and users
2) Control program: Manages 1) the execution of user programs to prevent errors, and 2) the operation of IO devices
“Switching on”/Execution of OS steps (3)
1) Loaded by bootstrap program.
2) Initializes OS.
3) Waits for 1st event.
Events are signaled by what?
Interrupts
What are the 2 types of interrupts?
1) Hardware signals
2) System calls
What happens when the OS receives an interrupt? (2)
1) OS stores the address of interrupted (current) instruction.
2) Transfers control to service routine.
What does the Interrupt vector do? (2)
1) Stores pointers to service routines.
2) Gets indexed by unique device numbers.
OS Organization consists of what? (3)
1) Interrupts
2) Storage
3) I/O Structure
Explain I/O Structure (3, 3rd:2)
1) Consists of Device controllers (Local buffers and registers), which move data between peripherals and buffers.
2) There is one Device driver per controller, allowing interface between the device controller and OS.
3) There are 2 kinds of I/O:
i) Interrupt driven I/O
ii) DMA I/O
Explain OS Structure (3)
1) OS provides environment within which programs are executed
2) Allows multiprogramming, by organizing jobs to keep the CPU as busy as possible and scheduling new jobs when the CPU is idle. (NB ‘Thrashing’)
3) Allows time-sharing through multitasking, frequent job scheduling, and interactivity due to response times <1s.
What is a process and what are process resources?
Process: A program in execution
Process resources:
CPU, memory, I/O, files that are later reclaimed upon process termination.
What does memory management entail? (2)
1) Keeping track of memory used and by whom.
2) Allocating and de-allocating memory.
What does Storage Management entail? (3)
1) File-system management through creation and deletion of files and directories, and mapping files/directories to data blocks.
2) Mass-Storage Management through free space management, storage allocation and disk scheduling.
3) Caching
What are protection and security i.t.c.o OS?
Protection: Mechanism for controlling access to resources.
Security: Defense of system against attacks. E.g., Denial-of-service, worms, viruses, identity theft.
