test Flashcards
What do shells do
allows user to interface with the OS
What do executables need?
OS servicces
How are executable performed ?
through system calls
What is a process ?
a program in exectuion
What is the address space of a process ?
memory locations which the process reads or writes to
PSW
Processor Status word contains control bits in CPU
Two modes of instructions
User mode = less privileged System mode = more privileged
What is an OS exception?
An abrupt change in Control flow in a response to a change in processor state
Exception: Interrupt
Signals from I/O
Exceptiom:Trap
Application request OS services
Exceptions:Faults
Recoverable error
Exception:Aborts
Not recoverable error
Kernel
Everything below the system call interface and above the physical hardware
What does the Kernel provide
- file system, -cpu scheduling
- memory management, other os functionality
What does a Kernel use?
System calls
Three catagories of system calls
1 File management, 2 Process control, 3 Information manipulation
What is a zombie
A process whose parent has excited/not waiting
What do process control blocks enable
Allows the CPU to resume the process where it left off when switching execution
What are the types of scheduling queues
job, Ready, Device
CPU scheduler vs long term scheduler
CPU is short term long term will try to balance CPU and I/O demand
What happens in context switches?
Old process state is saved new process is loaded
Process creation is based around
parent creating children
What is an orphan
Child whose parent has terminated
Pipes allow for communication on?
The same machine
Sockets allow for communication on?
Separate Machines
Error control approaches
Parity, CRC, Hamming
Flow Control: Stop and wait
Sever waits for client ack after each message
Flow Control: Pipeling
Sends ACK of next frame expected
Flow Control: Automatic Repeat Requests
Goes back and rejects new frames after error and ask for bad frames
High level data link
Station types. Primary controls secondary
Threads share?
Process Address Space and OS state
Two categories of thread implementation
User level threads and kernel level threads
Network Adress
Identifies a node
Routing
Forwards message to desitnation
Most networks can be broken into . . .
client and server and the client initiations communication
Network communicates data to the
Operating system
Operating system communicates data to the . ..
socket
Socket connects data to the
application
Two types of application Process communcation
Data gram and Stream
Data gram Socket
UDP Like post mail collection of messages connectionless
Stream socket
TCP Like telephone stream of bits connection oriented
Two types of network communication
Circuit switching and packet switching
Circuit switching
Dedicated path between two stations
Packet switching
Data transmitted in short packets that also hold control information such as destination
Security: Spread spectrum
Modulate the signal such that the bandwidth is increased significantly
Security: Frequency hoping spread spectrum
Sequence is seemly spread on random frequency each channel is used for fixed interval
TSL
Test and lock instruction
Synchronize clocks: Christians Algorithm
Ask twice for time use difference to calculate delay
Synchronize clocks: Berkely algortihm
Server polls client compute average time push result to client
Synchronize clocks: Lampert
Uses logical reasoning to set clocks
Resource allocation graph
R_1 -> P_1 resources R held by P R
Ostrich Algorthim for deadlocks
ignores them
Detecting deadlocks in a graph
DFS if node shows up twice deadlock is detected
Dead lock safe state
State where no deadlocks can occur avoid deadlocks by staying here
HLDLC: Normal response mode
+unbalanced, primary initiates, secondary only response
HLDLC: Asynchronous balanced mode
+ Balanced, either station may initiate, most widely used
HLDLC: Asynchronous Response mode
Unbalanced secondary initiates rare
