Chapter 1 Flashcards
What are the 4 components of a computer system?
Hardware, CPU, Memory, I/O Devices
Define Operating System
Controls hardware, similar to government in that it performs no useful function by itself, provides a workable environment
what type of OS when user sits in front of PC?
Ease of Use
what type of OS when user sits at terminal connected to a mainframe or mini-computer?
Resource utilization; equal share of CPU time, memory, and I/O devices
what type of OS when user sits at work stations and servers?
Compromise between ease of use and resource utilization
what is resource allocator?
especially important where many users access the same mainframe of computer
what is control program?
control program manages the execution of user programs to prevent errors concerning I/O devices
Moore’s Law
computers gained in functionality, and shrink in size, and decrease in cost
Kernel
Os running at all times
What are two types of programs?
Systems programs and application programs
Define Middleware
set of software frameworks that provide additional services to application developers
what is the initial program of OS?
boostrap program
R.O.M.
Read-only memory; storage that permanently stores data
EEPROM
electrically erasable programmable read-only memory known as firmware
example of firmware
smartphones
steps of general OS program
- bootstrap program locates OS kernel + load it into memory
- kernel provides services to system and its users
- interrupt from hardware or software
- CPU is interrupted; stops what it’s doing, and immediately transfers execution to a fixed location (fixed location contains starting address where service routine for interrupt is located)
- interrupt service routine executes, then CPU resumes the interrupted computation
Describe interrupts
- need to be handed quickly
- table of pointers used for speed
- interrupt vector holds addresses
RAM
Random access memory (main memory); rewritable and commonly is implemented in a semiconductor technology called dynamic random access memory (DRAM)
DRAM
dynamic random access memory
2 instructions used in storage structure
store & load
what does load do?
load moves a byte or word from main memory to an internal register within CPU
what does store do?
stores moves the content of a register to main memory
2 important reasons that things don’t stay in main memory permanently.
- main memory is too small to store all data and programs permanently
- main memory is a volatile storage device that loses its content when power is switched off
what storage holds larger quantities of data permanently?
secondary storage such as disks, cache memory, etc.
which storage systems are volatile?
registers, cache, main memory
which storage systems use semi-conductor memory?
registers, cache, main memory, and solid-state disk
what storage systems are non-volatile?
solid-state disk, magnetic disk, optical disk, magnetic tapes
faster storage system?
registers
slower storage system?
magnetic tapes
what is an example of solid-state disk
flash memory, seen in cameras (slower than DRAM, but needs no power)
NVRAM
Non-volatile DRAM
describe a function of cache
caches can be installed to improve performance where a large disparity in access time or transfer rate exists between two components
SCSI controller
small computer systems interface; 7+ devices can be attached to it
define device controller
device controller maintains some local buffer storage + set of special purpose registers, moves data b/w peripheral devices that it controls + local buffer storage
steps of I/O operation
- to start, device driver loads the appropriate registers within device controller
- device controller examines the contents of these registers to determine what action to take
- controller starts transfer of data from device to local buffer
- once transfer is complete, device controller informs the device driver via and interrupt that it has finished its operation
- device driver returns control to OS
DMA
Direct Memory Address
when is DMA more effective?
when some high-end systems use switch rather than bus
Other names associated to multiprocessor systems
parallel systems or multicore systems
3 main advantages of multiprocessor systems
- increased throughput (increased number of process, increase work in less time)
- economy scale (cheaper than multiple single processor systems
- increased reliability (more processes does not make it shut down, just slows down a bit)
Define graceful degradation
ability to continue providing service proportional to level of surviving hardware
what are systems that go beyond graceful degradation
fault tolerant (continue operation with a failure of a single component)
What are two types of multiprocessing?
- Asymmetric multiprocessing
2. symmetric muliprocessing (smp)
Describe Asymmetric multiprocessing
each processor is assigned to a specific task, boss processor controls system, workers look to boss for instructions or have predefined tasks
Describe Symmetric Multiprocessing
all processes are peers, each processor has its own set of registers, many processes can run simultaneously
Define Multicore
multiple computing cores on a single chip , and it uses significantly less power than multiple singlecore
blade servers
multiple processor boards, I/O boards, and networking boards, are placed in the same chasis
what are clustered systems?
multiprocessor systems, gathers together multiple CPUs
define clustering
usually used to provide high availability service, done so by adding a level of redundancy, can be asymmetric or symmetric
define asymmetrical clustering
one machine is in hot-standby mode while the other is running applications (hot standby machine only monitors active server, if server fails, hot standby host becomes the active server)
define symmetrical clustering
2+ hosts are running applications, more efficient
define parallelization
divides a program into separate components that run in parallel on individual computers in the cluster
DLM
Distributed lock manager; function that locks to ensure no conflicting operations occur
how is multiprogramming beneficial?
increases CPU utilization by organizing jobs so CPU always has one to execute
why are jobs initially kept on the disk in job pool
main memory is too small
define time-sharing (or multi-tasking)
logical extension of multi-programming and requires an interactive computer system which provides direct communication between user and the system
define process
a program loaded into memory and executing
define swapping
processes are swapped in and out of main memory to the disk
define virtual memory
enables users to run programs that are larger than actual physical memory
define trap ( or exception)
software-generated interrupt caused by either an error or specific request from user program
what are 2 separate modes of operation?
- user mode (1)
2. kernel mode (0): supervisor/privileged/system mode)
steps of operation using modes:
- mode bit is added to the hardware of the computer to indicate current mode
- distinguish between a task that is executed on behalf of OS or user
- if user then user mode
- if OS then step 3
- system must transmit from user to kernel mode to execute system call
purpose of dual mode?
protect OS from errant users, and errant users from each other
what are privileged instructions?
they can only be executed in kernel mode, if it attempts in user mode then it treats it as illegal and traps it to OS
define timer
timer is set to interrupt computer after a specific period of time in the event of an infinite loop, prevents a user program from running too long
define single-threaded process
has one program counter specifying the next instruction to execute
define file management
one fo the most visible components of OS
define caching
information is temporarily copied into a faster storage system - the cache. the management is an important design problem because of limited size
define cache coherency
update a value of ‘A’ in one cache is immediately reflected in all other caches where ‘A’ resides
how can protection improve reliability?
Detects latent errors at the interfaces b/w component systems
Define Bitmaps
string of n binary digits that can be used to represent the status of n items
Define disk blocks
medium-sized disk drive divided into several thousand individual units v
define accelerometer
detects tilting and shaking of device for augmented reality
TCP/IP
most common network protocol
LAN
local area network; within room, building
WAN
wide area network; cities, countries
MAN
Metropolitan-area network; metropolitan
PAN
personal-area network; phone to headset
define emulation
source CPU type is different from target CPU target
VMM
virtual machine manager
public cloud
cloud available to anyone willing to pay
private cloud
run by company
hybrid cloud
both private and public mix
SaaS
Software as a service: 1st applications via internet ex. gmail
Paas
Platform as a service: software stack ready for application ex. .net
Iaas
Infrastructure as a service: servers/storage over internet ex.Icloud
