Test Answers

1ai.
Share Files
Share one printer
Share internet connection
Less Secure

1aii.
Bit Rate - Faster if something needs immediate response
Data Content - Weather its Live (Real-time) or Delay e.g. Live = Faster needed, Real-time = Slower

1b.
Router - Divides the 2 networks
Modem - Converts Analog Signal to Digital Signal
Proxy -Monitors and restricts to and from Network
Firewall - Restricts access to Network

2a.
Protocol is a set of Rules for communication

2bi.
Bit Rate - Speed
Packet Switching - Transmission type
Parity Checks - Checks for errors

2bii.
Circuit Switching - Doesn't Break it up, Slower
Packet Switching - Sending data across multiple cables simultaneously in parallel

3.
Used as an error checker. Parity is based on checking if there is an even or odd number of ones. If an even number of ones are changed, an error is not reported/detected.

4a.
Checksums are a form of error detection in which the sum of a packet of bytes is found and is sent across to the target before the actual data. used as error detection. If the checksum is the same as the sum of the packet of bytes that arrives there is no error.

4bi.
Message Broken up. Whole Network used. Spread Message over whole network. Every available path. Reassembled at other end. Efficient use of Network

4bii.
Faster use of network
More Efficient
Harder to Hack
Faster but less reliable
More chance of errors

5ai.
One Bit

5aii.
One Byte

5aiii.
One Way Only

5aiv.
Two Way. One at a time e.g. Walkie Talkie.

5bi.
Even Number of ones to check for errors. If there is an even number of ones it will not display an error.

5bii.
If there is an even number of ones flipped no error will be displayed.

1.5g Protocols

 A Protocol in communications is a description or set of rules that sets the format for exchanging messages in or between computing systems. The rules include but are not limited too:

• Serial vs. Paralell
• Simplex vs. Full Duplex vs. Half Duplex
• Bit Rate
• Time Sensitivity
• Error Checking
• Authentication

1.5c Data Transmission

Serial and Parallel

Both transmit with binary
Bit Rate (BAUD)

Serial - sends 1 bit at a time
Parallel - sends 1 byte at a time. It is faster, but there is a higher chance for more errors, therefore less reliable.

Simplex

1 way communication

e.g. TV,Keyboard

Duplex Modes

Half Duplex

2 way communication (however only 1 can communicate at a time)

e.g. Walkie-Talkie

Full Duplex

2 way communication (both can communicate at the same time)

e.g. Phone, Ethernet

 

Thanks to Josh AsCompBlog

1.5a&b LANS and WANS

A) Describe the characteristics of a local area network (LAN) and a wide area network (WAN)

LAN

• 1 site
• switches/hubs
• ethernet

WAN

• 2+ sites/LANs
• Router
• Internet

Thanks to GBR Ascomp Blog

1.4e Common Peripheral Devices

Common Peripheral Devices

Input Devices

• Barcode Readers: Used to read barcodes
• MICR: Magnetic Ink Character Reader e.g machine used to process bank cheques
• OCR: Optical Character Reader e.g. Scanner software that reads the text scanned onto the computer so you can edit the text in a word processing program
• OMR: Optical Mark Reader e.g multiple choice answer reader and marker machine
• Scanners: Used to scan or copy an image of a document onto a computer
• Graphics Tablet: Can use a pen and 'pad' to draw an image onto the computer 

Output Devices

• Screens
• Printers

Thanks to Grace Benedek Rooney (Great Britain)

1.4d Transfer of Data, including Buffers and Interrupts

Buffers


Any Primary Memory (RAM or CPU) is much faster than any Secoundary storage.




Buffer = Small fast memory  to store data already dealt with

Stage 1: Processor -->  ALU --> Buffer  --> Hard Drive
Stage 2: Processor <->  ALU   Buffer  --> Hard Drive
Stage 3(Interrupts):         Processor <->  ALU   Buffer  --> Hard Drive --> CU --
                                                    |                                                                          
                                                 CU <---------------------------------------------------------^


Interrupt - A message from device to processor e.g. I have emptied the buffer now, can I have some more of the data


ALU = Arithmetic Logic Unit

1.4c Secondary Storage Media

Differences:

• Optical vs. Magnetic
• Sequential vs. Direct Access
• Max Size
• Portability
• Read Speed