Computer Science

Question 1

5 Uses of Hexadecimals

Answer 1

Memory Dumps
HTML
MAC address
Web address
Assembly or Machine code

Question 2

Memory Dump

Answer 2

When Memory contents of a computer are output to a printer or Monitor

Question 3

HTML

Answer 3

Hypertext Markup Language is a markup language used in the processing, definition and presentation of text.

Question 4

MAC address

Answer 4

Media Access Control address refers to a number which uniquely identifies a device on the internet, stored in the Network Interface Card which is part of the device.
Usually made up of 48 bits or 6 groups of hex
1st part- Identity number of the manufacturer
2nd part- Serial number of the device

Question 5

2 Types of MAC Address

Answer 5

UAA- Universally Administrated MAC Address (Common, Set by Manufacturer,)
LAA- Locally Administered MAC Address

Question 6

Asynchronous data transmission

Answer 6

Refers to data being transmitted in an agreed but pattern. Data bits (1s and 0s) are grouped together and sent with control bits.

Question 7

Synchronous Data Transmission

Answer 7

A continuous stream of data accompanied by timing signals generated by an internal clock.
Ensures sender and receiver are synchronised with each other.
Faster than asynchronous
Bits are then reassembled by the receiver.

Question 8

USB

Answer 8

Universal Serial Bus is an asynchronous serial data transmission method .
Standard method for transferring data

Question 9

Error-checking methods

Answer 9

Parity checking
Automatic repeat request
Checksum
Echo checking

Question 10

Internet service provider

Answer 10

ISPs are companies that provide access to the world wide web to users in return for a fee.
User account is set up and is given IP address.

Question 11

CSS

Answer 11

Cascading file sheet

Contains everything to control the actual presentation of the webpage

Question 12

HTTP

Answer 12

Hypertext Transfer protocol is a set of rules to be followed when transferring files across the internet

Question 13

Web browser

Answer 13

A web browser is a software which allows a user to display a web page by translating the HTML code.

Question 14

URL

Answer 14

Uniform resource locator

Question 15

OS

Answer 15

Operating system is software running in the background of a computer system. It manages many of the basic functions such as memory, processor management, multi-tasking, input and output control, running applications etc.

Question 16

When a computer is powered….

Answer 16

Initiating programs moves into the memory from ROM chip
These programs check whether hardware, processor, internal memory and bios are working correctly
Then operating system is then launched

Question 17

Interrupt

Answer 17

An signal from the software or another device to processor, which causes it stop what it is doing and service the interrupt.

Question 18

Buffers

Answer 18

Temporary memory area which allows data to be accessed much faster by the processor from hardware that operate at slower speeds

Question 19

Von Neumann architecture

Answer 19

Concept where computers store programs and data in a memory unit and instructions are fetched and executed one after another.

Question 20

5 registers in the model

Answer 20

PC-Program Counter
MAR Memory Address register
MDR Memory data register
CIR Current Instruction register
ACC Accumalator , which holds data being processed and the results of processing.

Question 21

3 types of buses and their features

Answer 21

Check pg 45 in textbook

Question 22

Fetch Execute Cycle

Answer 22

Current Instruction’s address is copied from the PC into the MAR, then the instruction at the address is retrieved from MDR then sent to the CIR.The value in PC is incremented by one. The instruction is decoded and executed.

Question 23

2D scanner process

Answer 23

The document is placed properly on the glass panel and the cover is then closed.
A bright white xenon lamp illuminates the document then a scan head moves across and scans the entire document which a lens focuses onto a CCD which converts the image formed into digital signals thereby creating a digital image.

Question 24

3D Scanners process

Answer 24

3D scanners make a digital model of a 3d object by taking several images at several points across the 3 coordinates. technologies used include CT (X-rays), MRI (Radio frequencies) and SPECT (gamma rays)

Question 25

Barcode process

Answer 25

Barcode read by red light or led
The black stripes absorbs most of the light while the white areas reflects most of the light.
The reflected light is read by a sensor.
The pattern generated is converted into digital data, allowing the computer to understand the barcode

Question 26

How digital camera works

Answer 26

The light passes through a lens onto a light sensitive cell made up of tiny elements called pixels.The number of pixels determines the size and resolution of the digital image

Question 27

Mouse how it works

Answer 27

Modern mouses use red LEDs to detect movement in x-y direction

Question 28

How microphones work

Answer 28

When a microphone picks up sound, a diaphragm vibrates producing an electric signal. These signals goes to a sound card and is converted into digital values and stored in the computer.

Question 29

Capacitive Touchscreen

Answer 29

Made of many layers of glass that act like a capacitor with electric fields created between them. When the top layer is touched,it causes a change in electric current and it's coordinates is determined by onboard microprocessor.
Durable
Medium cost
Multi touch
Visible in strong sunlight
Allows only the use of bare fingers

Question 30

INFRARED HEAT AND OPTICAL

Answer 30

Heat-sensitive
Uses glass as the screen material.
Needs a warm object (e.g. fingers) to carry out an input operation

Optical
Uses glass as the screen material
Uses an array of sensors (in the form of a grid); the point of contact is based on which grid coordinate is touched.

Benefits
Both systems allow multi-touch capabilities.
The optical system allows the use of bare fingers, stylus etc.
Very durable

Drawbacks
It is relatively expensive technology.
Heat-sensitive system only allows bare fingers
to be used for input (gloved fingers or stylus
don’t work)
Both systems (optical and heat-sensitive) have
fairly good screen visibility in strong sunlight.

Question 31

Resistive

Answer 31

This makes use of an upper layer ofpolyester (a formn of plastic) and a bottom layer of glass. When the top polyester layer is touched, the top layer and the bottom layer complete a circuit. Signals are then sent out which are
interpreted by a microprocessor, the calculations determine the coordinates
of where the screen was touched.

Benefits
It is relatively inexpensive technology
It is possible to use bare fingers, gloved fingers or a stylus to carry out an input operation

Drawbacks
Screen visibility is poor in strong sunlight.
It doesn’t permit multi-touch capability
The screen durability is only fair; it is
vulnerable to scratches and the screen
wears out through time

Question 32

Inkjet Printer

Answer 32

The data from the document is sent to a printer driver
The printer driver ensures that the data is in a format that the printer can understand
A check is made by the printer driver to ensure that the is printer available to print
The data is then sent to the printer and it is stored in a printer buffer
A sheet of paper is then fed into the main body of the printer; a sensor detects whether paper is available in the paper feed tray
If it is out of paper (or the paper is jammed) then an error message is sent back to the computer
As the sheet of paper is fed through the printer, the print head moves from side to side across the paper printing the text or image, the four ink colours are sprayed in their exact amounts to produce the desired final colour
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; this continues until the whole page has been printed.
More pages are printed until printer buffer is empty.
Once the printer buffer is empty, the printer sends an interrupt to the computer; this is a request for more data to be sent to the printer; the whole process continues until the whole of the document has been printed

Question 33

Laser printer

Answer 33

The data from the document is sent to a printer driver
The printer driver ensures that the data is in a format that the printer can understand
A check is made by the printer driver to ensure that the is printer available to print
The data is then sent to the printer and it is stored in a printer buffer
The start of the printing process involves a printing drum being given a positive charge; as this drum rotates, a laser beam is scanned across it removing the positive charge in certain areas; this leaves negatively charged areas which exactly match the text/images of the page to be printed
The drum is then coated with positively charged TONER
(powdered ink); since the toner is positively charged, it only sticks
to the negatively charged parts of the drum
A negatively charged sheet of paper is then rolled over the drum
The toner on the drum now sticks to the paper to produce an
exact copy of the page sent to the printer
To prevent the paper sticking to the drum, the electric charge on
the paper is removed after one rotation of the drum
The paper finally goes through a fuser which is a set of heated
rollers; the heat melts the ink so that it fixes permanently to the
paper
At the very end, a discharge lamp removes all the electric charge
from the drum making it ready to print the next page

Question 34

3D Printer Technologies

Answer 34

Direct 3D printing uses inkjet technology and the print head move up and down to build up the layers of an object

Binder 3D printing is similar to direct 3D printing. However, this method sprays dry powder and the secondly a binder (a type of glue ) is sprayed to form a solid layer.

Newer technologies are using lasers and UV light to harden liquid polymers; this further increases the diversity of products which can be made.

Question 35

3D printer process

Answer 35

CAD DESIGN
Special software converts the design into a format so it can be 3d printed
3d printer is set up
Solid object is built layer by layer (time taken depends on object)
Object removed and washed to remove support or other excess materials or to be left to cure for few hours

Question 36

LCD Monitor

Answer 36

Front layer is made up of liquid crystal diodes grouped together to form pixels (usually 3 colours- RGB, sometimes also yellow) and then back-lit using matrix of light emiting diode (LED) or 2 tubes of CCFL(Cold cathode fluorescent lamp)