678 - Chapter 1 Review

What is included in the User View of the OS?

Makes it easier to write programs, provides more powerful instructions than the ISA, makes it easy to run programs, utilities for multi-user mode operation

What is included in the System View of the OS?

OS as a resource allocator, OS as a control program

True or False: The IVT is at a fixed address in memory that is known to the CPU

TRUE - the CPU needs to know where the table is

How does the OS know what to do with an interrupt?

The interrupt has a number - go to the row in the IVT and execute the associative code in the table

What happens after the bootstrap program locates the OS kernel and loads it into memory?

The OS sits quietly and waits for events:
-hardware interrupts (sent to CPU over system bus)
-software interrupts (software error or system call)

What is the problem with batch systems?

Batch systems process one job at a time, one after the other (no overlapping) which means job 2 cannot start until job 1 finishes. I/O activity stalls the CPU (CPU is under-utilized). A job can be on EITHER CPU or I/O - whichever it is on, the other is idle

What is the goal of a MULTIPROGRAMMING OS?

To maximize throughput

Which is optimal for INTERACTIVE systems: multiprogramming OS or multitasking OS?

Multitasking (time sharing)

What is the goal of a MULTITASKING OS?

To optimize user response time

What prevents infinite loop / process hogging resources?

A timer - the OS sets a timer interrupt after a specific period, hardware decrements the counter, and when counter zeros generate an interrupt. Set up before scheduling process to regain control or terminate program that exceeds allotted time.

What is the difference between a program and a process?

A program is a passive entity while a process is an active entity (a process is a program in execution)

What is the difference between a single-threaded process and a multi-threaded process?

A single-threaded process has one program counter that specifies the location of the next instruction to execute (instructions are executed sequentially until completion) while a multi-threaded process has one program counter per thread

What is the OS responsible for in connection with process management?

-process scheduling
-suspending and resuming processes (sync access for shared resources)
-providing mechanisms for process synchronization
-providing mechanisms for process communication
-providing mechanisms for deadlock handling (deadlock: both waiting on the other to do something so neither is doing anything)

Memory management determines what is in memory when:

optimizing CPU utilization and computer response to users

What are memory management activities?

-keeping track of which parts of memory are currently being used and by whom
-deciding which processes (or parts thereof) and data to move into and out of memory
-allocating and deallocating memory space as needed

What is the difference between memory and storage in terms of duration?

Memory is transient while storage is permanent

Name some OS activities in regards to file-system management

creating and deleting files and directories, primitives to manipulate files and dirs, mapping files onto secondary storage, backup files onto stable (non-volatile) storage media

What is the I/O subsystem responsible for?

- Memory management of I/O including buffering (storing data
temporarily while it is being transferred), caching (storing
parts of data in faster storage for performance), spooling (the
overlapping of output of one job with input of other jobs) (spooling is used to store jobs and connect devices that work at very different speeds (i.e. printers)
- General device-driver interface
- Drivers for specific hardware devices

What is the difference between protection and security?

PROTECTION is a mechanism for controlling access of processes or users to resources defined by the OS while SECURITY is defense of the system against internal and external attacks (i.e. DOS, worms, viruses, identity theft, theft of service, etc)

What does privilege escalation do?

It allows users to change to effective ID with more rights (higher privileges = higher access; i.e. command "passwd" on Linux)