Chapter 7 Computer Artitecture Flashcards
how are HDD disks read?
The disk is continuously spinning and data is read/ written as the correct sector passes under read/ write head
How do HDD disks work
The disks are coated with a thin magnetic material changes in the direction of magnetism represent 0s and 1s
How is a HDD disk split up?
The disk is divided into tracks and sectors
(tracks are concentric circles, sectors are blocks)
How do optical disks store data
data is stored as a series of bumps/ pits within the track
How is an optical disk protected?
A protective layer is put over the surface to prevent corruption
How is optical disks read?
A laser reads the pits and lands which then interprets an electrical signal
What 3 things do you need to say when asked to describe the “principles of operation” of an SSD.
It uses NAND flash memory
and floating gate transistors which are used to trap and store charge
Data must be written in pages and erased in blocks
Secondary Storage definition:
Permanent memory not connected to the processor, used to store data when the computer is turned off.
How does a bar code scanner work?
An infered light is shone at a bar code
The light is reflected back
Black/ white bands on the bar code reflect difference amounts of light (black less and white more)
Light sensor measures the amount of reflected light. This light is convereted into an electrical signal.
Electrical signal analyed to determine the vlaue encoded in bar code.
Positives of barcodes
Cheap, quick to read and can be read at different angles
Negatives of barcodes
Limited amount of data can be stored
How does an RFID reader work?
Read emits electromagnetic waves
The RFID tag is energised by the waves
The tag sends back the data signal via radio waves
The reader receives the radio signal
Positives of RFID readers
Can be read without physical contact
Negatives of RFID readers
Multiple RFID cards together can interfere with signal, thieves can interfere with your card without contact, more expensive to produce than bar codes
How does a digital still camera work?
The shutter opens and lets light in through the lens,
the light is focused onto a sensor usually a charge coupled device CCD
the sensors are made up of millions of transistors, each stores the data for a pixel
as the light hits the sensor the amount of charge is recorded for each pixel as binary
If it is a colour camera then the camera can use three different sensors for (R, G and B)
Positives of Digital still cameras
You can see the images before developing them
Negatives of Digital still cameras
THe quality of traditional photos is better than digital photos
How does a laser printer work?
A rotating drum inside the printer is coated in a chemical which holds and electrical charge
The laser is reflected onto the drum via a rotating mirror
The laser neutralises the electric charge on the drum where the image should be black
Toner is given a positive charge and the drum picks up this toner
Drum is rolled onto the paper, the toner is transfered to the paper
The paper is heated to fuse the toner onto the paper.
How do you create a for loop in assembly?
First write down a word to bridge to
Then add #1 to a register
then do what you want to be looped
then compare the register to the number of times you want it looped + 1 and if they arent equal bridge to the word
What is the opcode?
The operation e.g. ADD, LDR
What is the Operand
THe data being used e.g. a number or an address
What is a low level langauge?
A language that is very similar (or based upon) the instruction set of the computer requiring very little translation
What is a high level language?
High level languages are similar to human language.
What is the definition of an algorithm?
A series of instructions to solve a problem that always terminates
What is the definition of encryption
Make a file not be able to be read without a key.
What is a utility program
A prgram that helps manage the hardware i.e firewall
What is a complier
Translates high level code all at once into machine code
What is an interpreter?
Translates high level code line by line into machine code
What does multi-core mean
A computer with more than one processor this increase system performance and the number of instructions executable per second
What is cache memory
Temporary memory that is separate from main memory so it can be accessed quicker due to its closer proximity. Increasing cache is likely to increase system performance and the speed at which stuff can be accessed
What is word length in terms of processor performance?
The number of bits in a binary word.
What is bus width?
The number of signal wires allocated to the bus
What impact would increasing the word length have on the processor performance?
The greater the number of operations and the larger the range of results
What impact would increasing the data bus length have on the processor performance?
Increases the number of bits sent at once.
What impact would increasing the address bus length have on the processor performance?
Increases the number of addressable memory locations
What is recursion
THe process of a subroutine calling itself
What is the control unit?
Fetches program instructions from meomory and decodes them one at a time
What is the arithmetic and logic unit?
The ALU performs all arithmatic and logic functions
What is a registeR?
Fast memory locations inside the processor
What is the internal clock
Derives from system clock works to synchronise the components of the computer
What are the internal buses
Several internal buses link all the components
WHat does the program counter register do?
Points to the next instruction to be fetched
What does the status register do?
Holds condition codes to indicate the outcome of operations
What does the current instruction register do?
Holds the current instruction to be executed
What does the memory address register do?
Holds the address of the memory being currently accessed
What does the memory buffer register do?
Holds the data item currently being accessed
Which bus can everything read and write to?
The control bus
Which bus can only the processor write to?
The address bus
Which bus do input devices usually only write to?
The data bus
Which bus do output devices usually only read from?
The data bus
Which bus can both the processor and the storage devices can read and write to?
The data bus
What is an I/O controller?
An electric circuit that connects to a system bus and an I/O device and interfaces between them
Allows the processor to communicate with a peripheral without having to redesign the processor.
What happens in the fetch stage of the fetch, decode and execute cycle?
Contents of the PC are transferred to the MAR
Address bus transfers this address to main memory, contents of the addressed memory transferred to the MBR via data bus.
At the same time, PC counter incremented by 1
Contents of the MBR transferred to the CIR
What happens in the Decode stage of the fetch decode execute cycle?
Instruction held in CIR is split into opcode and operand and is decode by control unit
What happens in the execute stage of the fetch decode execute
If necessary, data is fetched. Relevant part of processor executes instruction, status register is updated, result stored in accumulator.
