4.7: section 5: computer organisation and architecture

Question 1

name 6 internal components in the central processing unit

Answer 1

• processor: Responds to and processes the instructions that drive the computer.
• main memory: stores data and instructions that are to be processed
• address bus: -sends the memory address of a word from the processor to CPU components
• control bus: Sends control signals/lines between the I/O controllers and the processor
• data bus: -sends data and instructions between CPU components
• I/O controller: receive input and output requests from the processor and send device specific controls signal to the device

Question 2

what is von Neumann architecture

Answer 2

• instructions and data must be stored in the main memory to be executed
• the machine code instructions are fetched from the memory one at a time using the same bus and decoded and executed by the processor

used extensively in general purpose computing systems

Question 3

what is Harvard architecture

Answer 3

• has separate memories for data and instructions
• has separate buses for data instructions
• used embedded Digital Signal Processing (DSP)
• faster than Von Neumann as the instruction and data can be fetched at the same time

Question 4

what type of systems use Harvard architecture

Answer 4

• used with embedded digital signal processing
• embedded systems include special purpose built in computers which operate in real time
• e.g. traffic lights, navigation systems, aircraft flight control systems

Question 5

what is the stored program concept

2 points

Answer 5

machine code instructions stored in main memory are fetched and executed serially by a processor that performs arithmetic and logical operations.

Question 6

what is addressable memory

4points

Answer 6

Memory is divided into units called words.

Word: a fixed size group of digits, typically 8, 16, 32 or 64 bits

• Each word has its own specific memory address
• when a processor wants to read a word of data from the memory it puts the address of the word onto the address bus

Question 7

what is a processor instruction set

Answer 7

-the group of instructions that a processor can carry out.

-Each type of
processor has its own instruction set, so instructions for one processor may not be
compatible with other processors.

-usually stored in machine code

Question 8

what are the 6 typical instructions included a processor instructions set

Answer 8

• data transfer
• arithmetic operations
• comparison operators
• logical operators
• branching
• halt

Question 9

what is opcode

Answer 9

• the operation code which corresponds to an instruction

- this will include the addressing mode

Question 10

what is the operand

Answer 10

-the data value the operation is acting on

Question 11

what is immediate addressing

Answer 11

-where the value represented in the operand is the actual data value

Question 12

what is direct addressing

Answer 12

-where the value represented by the operand is the memory address holding the data

Question 13

what are barcodes and the two types

Answer 13

printed diagrams made of light and dark portions which contain information computers can read with a barcode reader.

there are 1d and 2d barcodes

Question 14

how do 2d barcodes differ

Answer 14

contain more information in the same amount of space but require more processessing to extract content

Question 15

what are barcode readers made up of

Answer 15

laser light source
lens
photodiodes
mirror

Question 16

how do barcode readers work

MLPLP

Answer 16

1. mirror directs light from the laser onto the barcode
2. light reflected by barcode passes through lens and is incident on the photodiode
3. photodiode turns light into electrical charge which can be measured and processed to form a digital signal
4. light portions of diode reflect most light wile dark portions absorb
5. pattern of light and dark stripes in barcode correpsponds to inary 1s and 0s

Question 17

what are digital cameras made up of

Answer 17

lens
sensors: CMOS, CCD
cells
shutter
filter-coloured cameras

Question 18

how do digital cameras work

LSCS F

Answer 18

1. lens focuses light onto sensor
2. sensors convert light into electrical charge
3. sensors are made up of cells which represent pixles in the final image
4. shutter regulats the path of light between the light and sensor
5. in colour cameras there are multiple cells per pixel
6. each cell has a filter that only allows a certain wavelengt of light.
7. bayer filters have the same number of green, blue and red filters that let cameras produce images close to what the human eye sees

Question 19

what are laser printers made up of

Answer 19

laser light source
mirror
drum
toner roller
fusers

Question 20

how do laser printers work

DLI TN TP F

Answer 20

1. drum is positively charges
2. e laser is directed at its surface by the mirror. Areas on which the laser is incident are discharged,
3. this leaves an impressions of the page in electrical charge
4. toner roller dispenses negatively charged toner onto the drum
5. toner is attracted to positively charged portions of the drum and is applied to paper
6. paper is heated by fusers which fixes toner to paper
7. colour printers use the same process but have 4 colours of toner CYMK

Question 21

what are RFID tags made up of

Answer 21

chip with a small amount of memory

coil of wire attachted to chip/antenna

Question 22

what are RFID tags for

Answer 22

radio frequency tags are a method of tranferring information wirelessly between a taga and a reader

Question 23

what are two types of RFID tags

Answer 23

passive: inducing enough power form reader to operate chip

active: contain a small ower supply like a battery
they can be read from much further away than passive tags

Question 24

how do RFID tags work

RPAD

Answer 24

1. reader emits radio waves which are picked up by tags antenna
2. power induced from these waves is enough to power a passive tag’s chip
3. the chip uses its antenna to emit a radio wave containING its information
4. the wave is picked up by the reader hich decodes the information

Question 25

what type of sotrage is primary storage

Answer 25

volatile RAM and ROM

Question 26

what type of storage is secondary storage

Answer 26

non volatile storage is used to store files and applications

Question 27

what are hard disk drives

Answer 27

a secondary storage device made up of a number of circular platters from a magnetic material

they are typically between 500GB and 5TB

they are suseptible to damage form movement

Question 28

how do hard disk drives work

APADR

Answer 28

1. above each platter hovers an actuating arm where the read/write head is mounted
2. the read/write head changes magnetic polarity of parts of the platter
3. the actuating arm allows the read/write head to access all parts of each platter
4. data is written in concentric track-each is divided into sectors
5. the platter rotates thousands of times per minute allowing good read/write speeds

Question 29

how can you increase hard disk drive capacity

Answer 29

add more platters

decrease width of tracks

Question 30

what are solid state drives

Answer 30

a secondary storage device mad of non volatile NAND flash memory cells and a controller

not capable of overwriting data so it must be completely erased to write new information to it

has no moving parts

Question 31

how is information stored on solid state drives

Answer 31

1. memory cells are formed of floating gate transistors which store information by trapping electical charge
2. data is stored in pages which combine to make blocks

Question 32

what are optical disks

Answer 32

secondary storage in the form of CDs, DVDs and Blue-Ray which can be read optically by laser

they can be read only, recordable or rewritable

they have one continuos track that sprials from the disk centre

Question 33

how do read only disks work

SBPC

Answer 33

1. stores data using pits and lands
2. pits are burnt into the disk with a high powered laser
3. a low powered laser beam is passed over the surface
   - when the laser passes a land the beam is reflected onto a photodiode
   - when the laser passes a pit the beam is scattered

4.the pattern of reflections and scatters can be converted into digital signals

Question 34

how do recordable and rewritable disks work

ORAP

Answer 34

1. a pattern of reflectionsa and scatters is created by an opaque dye on the disks surface
2. if there is no dye the beam is reflected of the optical disks surface
3. if there is dye the laser beam is absorbed
4. recordale disks use a photosensitive dye which changes form opaque to transparent under a high powered laser