components of a computer system Flashcards
what happens in the fetch?
-copy mem. add. from PC to the MAR
-copy instruc. stored in MAR to MDR
-increment PC to point to the add. of next instruc. ready for next cycle
what is a processors clock speed?
how many instructions can be carried out per unit time (on a single individual core)
the speed at which the FDE cycle happens
-measure in Hz, 1 cycle per second
purpose of an electronic computer:
-takes input
-processes data
-delivers output
purpose of ALU (arithmetic logic unit)
performs calcs and logical decisions
Control Unit (CU) purpose:
decodes instructions
sends signals to control how data moves around CPU & memory to execute those instructions
what is cache?
-store of temp data
-provides fast access to frequently used instructions and data
what are registers:
tiny, super fast pieces of onboard memory inside CPU designed to hold temporary data during FDE cycle
components in a VNa (von neumann architecture)
-control unit (CU)
-ALU
-Memory Unit (RAM)
-inputs and outputs
what registers does a von neumann contain:
-program counter (PC)
-memory address register (MAR)
-memory data register (MDR)
-accumulator
what is the decode:
-instruction in MDR decoded by CU
-CU may then prepare for next step eg. by loading values into MAR or MDR
what is execute:
-eg. of what it may execute
-instruction performed. could be: write data to mem, load data from mem, halt program etc.
what is cache
-very fast memory in CPU, slower than registers but faster than RAM
characteristics that affect performance:
-clock speed
one GHz= 1 billion Hz instructions per sec
-cache size
-no. of cores
cores are complete copies of the CPU
what are embedded systems?
-advantages?
computer system built into another device
-easier to design, cheaper, more efficient at doing their task than general purpose comps
what is primary storage?
-RAM, ROM, registers and cache
why is sec storage needed?
-because ROM is read-only and RAM is volatile
uses of sec storage?
-storage of data and programs when power is off
-archiving files
-semi permanent storage of data that can change
-backup files
what is the role of a program counter
-holds memory address of the instruction for each cycle
-program counter (PC):
stores the memory address of the next instruction in program to be executed
-once fetched, contents incremented by 1 so it can point to next instruction
-memory address register (MAR):
holds address of where data is to be fetched or stored
-memory data register (MDR):
holds the data fetched from, or to be written to memory
-accumulator:
holds results of calculations by ALU and and value of inputs and outputs to and from CPU
how to work out text file size
bits per character x no. of characters
bits to bytes
/ by 8
work out image file size
colour depth x image height x image width
bytes to KB
/ by 1000
sound file size calculation
sample rate (Hz) X duration (s) x bit depth x no. of channels
what can you do if you run out of main memory
Purchase more RAM
Virtual memory
Terminate processes (close programs)
common units of storage:
Bit 1 or 0
Byte 8 bits
Kilobyte (KB) (1000 bytes).
Megabyte (MB) (1000 KB).
Gigabyte (GB) (1000 MB).
Terabyte (TB) (1000 GB).
Petabyte (1,000 TB).
features of solid state drive
- medium storage capacity
- very quick to access data
- no moving parts, very reliable
- no noise
- low power
- no need to be defragmented
- limited number of read/write cycles
- expensive compared to other storage
define drive & media
drive: the device that reads and writes data from sec storage
media: what the data is actually stored on
features of optical disks
- low capacity compared to other types of storage
- slow to access data
- thin, lightweight and portable
magnetic hard disk features
- high storage capacity
- quick to access data
- has moving parts, which will eventually fail
- hard disks perform better if they are defragmented
requirement of deciding for storage device
- capacity
- speed
- portability
- durability (in terms of will it get damaged by shocks, scratches etc.)
- reliability (in terms of how many times can it be used)
- cost
suitability of optical storage
suitable for:
- read only data distribution on a large scale
- small capacity situations
suitability of magnetic storage
suitable for:
- when very high data capacity is required
- fast access to data
- low cost situations
- cloud storage on server farms
suitability of solid state storage
suitable for:
- low power, small embedded systems
- rugged applications: portable devices
- small to medium data capacity requirements
- silent operation
- very fast access to data
- situations where the device needs to be small and lightweight
examples of optical storage
CD (700 MB), DVD (4.7 GB), Blu-Ray (25 GB)
examples of magnetic storage
hard disk drive
magnetic tapes
examples of solid state storage
solid state drive
memory sticks
flash memory cards
why using a CPU with a large cache capacity may increase CPU performance
- cache is much faster than RAM
- larger the cache, the more data can be stored for quick access by the CPU
thus, better performance
explain the difference in improving performance of CPU by increasing clock speed and increasing no. of cores
-inc. clock speed:
more instructions can be carried out per unit time on each individual core
-inc. no. of cores:
more instructions can be run simultaneously
benefits of increasing core count
-better running multi-thread processes
-more instructions executed simultaneously
benefits of increasing RAM
-allows more programs to be opened at same time
-less likely to need to use virtual memory
differences betw an embedded system and a smartphone
EM: computer built into an electronic device
SM: the computer is the entire device
SM: built on open operating-systems, making them general purpose devices eg. Word
EM: limited RAM
SM: many have desktop-computer level RAM capacity
significance of fe cycle in von - neumann architecture
-program/instructions stored in primary mem
-instructions can be copied into CPU before they can be executed
Pros and cons of magnetic storage
suitable uses
pros
- cheaper per GB
- can have high capacity (cheaper)
cons
- slower read write speeds
- higher energy usage
uses
- main secondary storage on cheaper PC’s (HDD)
- incremental server backups (HDD)
- long term backups (tape)
Pros and cons of solid state storage
suitable uses
pros
- faster read write speeds
- lower power consumption
- higher capacity (at a price)
cons
- more expensive per GB
uses
- transferable media (SD card, USB, flash device)
- main secondary storage on more expensive PC’s where speed is critical (SSD)
Pros and cons of optical storage
suitable uses
pros
- thinner media
cons
- more expensive per GB
- media easily damaged
- r/w units become harder to find
uses
- distribution of data in magazines
- distribution of media (DVD, CD, Blu Ray)
what is a character set
set of all characters
recognizable by a processor
difference between Unicode and ASCII
- unicode is made up of more bits per character
- unicode has more unique values
define resolution
Number of pixels (in an image)
describe the FDE cycle
Fetch
- copy mem address from PC to the MAR
- copy instructions stored in the MAR to the MDR
- increment PC to point to the address of next instruction ready for the next cycle
Decode
- instructions in the MDR decoded by the CU
- CU then repairs for next step eg, by loading values into the MDR or MAR
Execute
- instruction performed
purpose of operating system
provides a platform on which users can run applications
purpose of utility software
used to maintain the computer system
the two types of system software
operating systems
utility software
feature of GUI (graphical user input)
-windows, icons, menus, pointers (WIMP)
-visual
-interactive
-intuitive
-optimised for mouse and touch gesture inputs
features if CLI (command line interface)
-text based
-less resource heavy than GUI
-more commands than GUI
-efficient
-for advance users
-useful for automating processes w/ scripts
features of a MI (menu interface)
-successive menus presented to user
-single options chosen at e/ stage
-often w/ buttons on a keypad
features of NLI (natural language interface)
-responds to spoken language
-not always reliable
-getting better
multitasking in computing
-run multiple applications at same time by giving each a small time-slice of processor time
-allows more than one program to be held in memory at a time, data shared betw/ them
memory management in computing
-when programs loaded, OS decides where they’re held in memory
-as programs closed and and loaded, memory becomes fragmented as they used diff amounts of memory
-when memory full, OS uses virtual memory
device drivers functions
Translates OS instruction into commands hardware will understand
-each peripheral needs device driver
-many already built into OS
Ways to make use of file management facility:
He can place his files into folders/directories
He can (re)name files/folders
He can move his files/folders
He can delete his files/folders
He can search for files
He can create files/folders
He can open files/folders
