Chapter 3. Hardware

Question 1

What are the two types of memory and their example

Answer 1

1. Primary
   -RAM
   -ROM
   2.Secondary
   -HDD
   -SSD
   -Removable items

Question 2

Why is RAM called random access memory

Answer 2

Because any memory location can be accessed regardless of the last memory location to be used

Question 3

What are the two types of RAM

Answer 3

DRAM and SRAM

Question 4

Explain how DRAM works internally

Answer 4

DRAM has capacitors and transistors. The capacitors hold bits of information (either a 0 or a 1) and the transistors act like switches; they allow the chip control circuitry to read the capacitor or change the capacitors value.

Question 5

Differentiate between DRAM and SRAM

Answer 5

<b>DRAM</b>
-uses capacitors and transistors
-needs to be constantly refreshed
-less expensive to manufacture
-has a higher memory capacity
<b>SRAM</b>
-uses flip flops to hold data
-no need to be constantly refreshed
-faster data access time
-at high frequencies power consumption can be more than DRAM

Question 6

Differentiate between RAM and ROM

Answer 6

<b>RAM</b>
-temporary memory device
-volatile
-can be read and written to
-used to store data, files, programs, part of OS currently in use
-can be increased in size to improve operational speed of a computer
<b>ROM</b>
-permanent memory device
-non-volatile
-data stored cannot be altered
-sometimes used to store BIOS and data other data needed at startup

Question 7

How does PROM work

Answer 7

A type of ROM that can be altered once. It is made up of a matrix of fuses. A prom writer uses an electric current to alter specific cells by burning fuses in the matrix

Question 8

What are the pros of an embeded system

Answer 8

-small in size and therefore easy to fit in devices
-relatively low cost to make
-usually dedicated to one task, making for simple interfaces and often no requirement of an operating system
-consume very little power
-operate in real time(fast reaction to changing input)
-with mass production comes reliability

Question 9

What are the cons of embedded systems

Answer 9

-difficult to upgrade
-troubleshooting faults in the device becomes specialist work
-although the interface can appear to be simple, in reality the system will take more steps to do a simple task
-ay device that can be accessed over the internet is also open to hackers, viruses and so on
-wasteful since its difficult to upgrade

Question 10

What are the three categories of secondary devices and give examples of each

Answer 10

1.magnetic
-HDD
-magnetic tape
-floppy disc
2.solid state
-SSD
-SD cards
-flash drives
3.optical
-CDs
-DVDs
-Blu-ray discs

Question 11

Define latency

Answer 11

the delay before a transfer of data begins following an instruction for its transfer

Question 12

Define fragmentation

Answer 12

it is when a collection of data in memory is broken up into many pieces that are not close together

Question 13

What do you understand by flash memory

Answer 13

solid state storage devices that use NAND technology rather than EEPROM(NOR technology)

Question 14

Benefits of SSDs

Answer 14

-more reliable as there are no moving parts
-considerably lighter
-lower power consumption
-run much cooler than HDDs
-thinner and faster

Question 15

Describe birefringence

Answer 15

When dual layering cause light to refract into two separate beams causing reading errors

Question 16

Describe steps taken by a laser printer

Answer 16

-data from the computer is sent to the computer
-printer driver makes sure that the data is in the right format
-printer driver checks if the printer is ready to start printing
-data is stored in the printer buffer
-printing drum is given a positive charge. the drum rotates and a laser removes the positive charge on certain areas
-drum is coated with positively charged toner(powdered ink)
-negatively charged sheet of paper is put on the roller
-toner sticks to paper
-after one rotation the charge on the paper is removed
-the paper goes through a fuser where the ink is melted and becomes permanent on the paper
-a discharge lamp removes all the charges on the drum

Question 17

What are the components of an inkjet printer

Answer 17

-a print head consisting of nozzles
-an ink cartridge or cartridges
-a stepper motor and a belt which moves the print head assembly from side to side
-a paper feed which automatically feeds the printer with the pages

Question 18

Describe the two technologies in inkjet printers

Answer 18

1. Thermal bubble
   -tiny resistors create localized heat which makes the ink vaporize. this cause the ink to form a tiny bubble, as the bubble expands some pf the ink is ejected from the head. when the bubble collapses it creates a vacuum and more ink is drawn to the head
2. Piezoelectric
   - a crystal is given a tiny electric charge which makes it vibrate . this vibration forces the ink to be injected onto the paper and at the same time the ink is drawn to the ink head

Question 19

Describe steps in an inkjet printer

Answer 19

-a sheet of paper is fed into the main body of the printer
-the print head moves from side to side across the paper spraying ink on the page
-at the end of each full pass of the print head, the paper is advanced very slightly to allow the next line to be printed

Question 20

What is the difference between CNC machining and 3D printing

Answer 20

CNC uses subtractive manufacturing whilst 3D printing uses additive manufacturing

Question 21

What is CNC

Answer 21

Computer Numerical Control (CNC) machining is a manufacturing process in which pre-programmed computer software dictates the movement of factory tools and machinery. The process can be used to control a range of complex machinery, from grinders and lathes to mills and CNC routers

Question 22

What is the difference between Direct 3D printing and Binder 3D printing

Answer 22

Direct 3D uses inkjet technology whilst binder 3D uses two passes for each of the layers; the first pass sprays dry powder and then the second a binder(a type of glue)