Paper 1 Exam Questions Flashcards
Compare the use of ASCII and Extended ASCII to represent characters
1 mark per bullet, max 2.
Extended ASCII uses more bits // ASCII uses fewer bits
Extended ASCII can represent more characters //
ASCII can represent fewer characters
… by example (e.g. extended ASCII can represent
European symbols / other languages)
1 (a) A radio station records an interview with a computer scientist using a computer and audio recording software.
(i) Explain how sampling is used to store audio recordings.
Height/amplitude of waveform is sampled/measured
Converted to / stored as binary/digital
Sample / measurements taken at a regular interval / set interval / by sensible example (eg 44,000 times per second)
The radio station uses a digital camera to take a photograph of the computer scientist for their website. The photograph is stored as a bitmap image.
(i) Describe how bitmap images are represented in binary
Image made of / split up into pixels
Each pixel given a binary code which represents the colour of that pixel
Each colour is given a different/unique binary code.
Metadata stored alongside the image
(ii) Explain why computers represent data in binary form.
Computers consist of transistors / switches / logic circuits / gates which only have two values / on or off / 1 or 0 / open or closed
Explain the advantages of lossy compression
Advantages
File size is reduced / gets smaller // image contains less data
..so quicker to upload / download / load / transfer
…takes up less storage space // space on the web server
…less (mobile) data usage
Explain the disadvantages of using lossy compression
Disadvantages
Quality of image is reduced (compared to original)
…because data is lost / removed // by example (eg fewer colours / lower resolution)
…reduction is permanent / not reversible
Remember
- sound file size = sample rate(Hz) x duration (it has to be in seconds) x bit depth
- Analogue sounds must be stored in binary
- image file size = colour depth x image height (px) x image width (px)
- text file size = bits per character x number of characters
Remember
o Bit o Nibble (4 bits)
o Byte (8 bits)
o Kilobyte (1,000 bytes or 1 KB)
o Megabyte (1,000 KB)
o Gigabyte (1,000 MB)
o Terabyte (1,000 GB)
o Petabyte (1,000 TB)
OCR Land regularly emails discount codes to customers. Each discount code includes a check digit as the last character.
(i) Give one benefit of using a check digit for the discount code.
Check that the code is valid / real
Check it has been entered / sent / received correctly.
Makes it harder for people to make up discount codes
Describe how a character set is used to represent the string value stored in the variable “name”
- Each character in character set has a unique binary number/value
- Each character in the string is assigned its associated number/value
- The binary value of each character is stored/combined (in order)
- … by example e.g. The binary value for D, then for r, then for u
• Uses ASCII/Extended ASCII/Unicode
Give two reasons why computer scientists use hexadecimal to represent numbers instead of binary
- Easier/quicker to communicate / enter / write / read / remember
- Less chance of input errors
- They are shorter
- Easy to convert between binary and Hexadecimal
(a) State what is meant by the term image resolution[1]
5 a)
• Number of pixels (in an image)
OR
• Height and width (of an image)
(b) Calculate the fewest number of bits that could be used to store the logo as a bitmap image. You must show your working. [4]
- 15* 6 = 90 (pixels in an image)
- Multiply pixels x bits per pixel
- …2 bits required per pixel because there are 3 colours
- 180 bits overall answer
(c) Give two ways that the file size of the image could be reduced.[2]
- Reduce number of pixels / resolution
- Reduce number of colours
- Use lossy compression
- Use lossless compression
What is the role of switch
A switch performs a similar role to a hub and a bridge but is more powerful. It stores the MAC addresses of devices on a network and filters data packets to see which devices have asked for them. This makes a switch more efficient when demand is high. If, for example, a game involved lots of data being passed between machines, then a switch could reduce the amount of latency.
What is NIC
A network interface controller (NIC) provides a method of connecting to a network. A NIC offers an interface port for a wired connection. A wireless NIC provides a radio transceiver for connecting wirelessly.
What is a IP address?
When connected to a network each device is given a unique IP address. This address consists of four sets of up to three digits, each with a maximum value of 255, which are separated by dots. An example is:
192.168.0.254
When a node wants to send a message to another node, it uses the recipient node’s address as the destination. A switch on the network knows where the node with this address is and routes the message to it accordingly.
What is a transmission media
Transmission media carry data signals from one computer to another. Media are either wired or wireless.
In modern networks, wired media use either twisted copper wiring, or fibre-optic cable. Each wired medium has differing characteristics
Compare wireless and wired connections
Wired connections are reliable and not usually subject to interference. However, they limit mobility - a wired device usually has to stay in place.
Wireless connections use radio waves to carry signals. These signals are limited in range (usually up to 50 metres), but are subject to magnetic interference - they can also be blocked by walls. However, they are ideal for mobile devices as a device can connect to a network as long as it is in the range of a wireless access point.
William can choose between a full or incremental backup.
- *Identify the backup method William should use to backup the computer, justifying your**
- *choice.**
Incremental:
Only the changes need to be backed up
The software/OS/settings are unlikely to have changed between backups
Small number of files likely to be used/edited between backups
Take less time to backup
Each backup will take less memory space to store
Full:
Backup all the data/files and software
It might not take a significant time to back up entire system
He might only have a small number of files to be backed up each time
Faster to restore the backup
Needs to do a full before he can do an incremental
(c) (i) Describe the purpose of the router in the house’s network.
Directs packets/data to destination // directs packets/data in a network
Receives packets/data from the network/Internet
Forwards packets/data to other computers on the network/Internet
Connects (different) networks together // e.g. joins home network to Internet
Has (public) IP address for LAN
Designates (private) IP addresses to network nodes
A small island has 100 people living on it. The island has just been connected to the Internet, after
previously having no Internet or mobile phone signal.
Discuss the impact on the island’s inhabitants and businesses of getting access to the Internet.
In your answer you might consider the impact on:
• inhabitants
• businesses
• ethical issues
• privacy issues
Inhabitants
Connection with the rest of the world
Access to more information
Up-to-date with news
E-commerce
Communication with people
Can be used in schools/for education
Cost (Devices and connection)
Businesses
Sell products to wider audience//more customers
Purchase items from wider range/more places
Competitive prices
Tourism can be advertised
Online bookings for hotels
Ethical issues
Access to inappropriate/illegal content
Lead to social pressure to be online and get technology
Cost
Introduces digital and social divide
Threats
Privacy issues
Tracking of IPs/devices
Social media
Unwanted images and videos of people may be put online
Risk of threats e.g. phishing/pharming/virus
The CPU has a clock speed of 3.8 GHz.
Describe what is meant by a clock speed of 3.8 GHz.
The number of FDE cycles run per given time/second // the frequency that the clock ‘ticks’
3.8 billion cycles/instructions per second
Alicia says:
“My computer has a quad-core processor, so it will run twice as fast as a computer with a
dual-core processor.”
Explain why this statement is not always true.
Software may be designed to run on 1 core and not multiple cores
Clock speed also affects speed
RAM size also affects speed
Cache size also affects speed
The computer will only have 2GB of RAM, but Alicia says that virtual memory can be used
instead of adding more RAM.
(i) Explain how virtual memory can compensate for the lack of RAM in Alicia’s computer.
VM is used when RAM is full
Data from RAM is moved to the secondary storage/VM to make space in RAM
RAM can then be filled with new data
When data in VM is needed it is moved back to RAM
Explain why it would be beneficial for Alicia to get more RAM instead of relying on virtual
memory.
More RAM will improve the performance of the computer // More RAM will speed up the access to data
Excessive use can cause disk thrashing which decreases performance
VM is slower to access than RAM direct (because it has to go back to RAM first)
Moving data between RAM and VM takes processor time
What is the difference between IMAP and SMTP
IMAP
Retrieves/accesses/downloads (a copy of an) e-mail
Allows synchronisation/management of account
SMTP:
Sends/forwards/transmits e-mail
The utility system software provides compression software. Xander uses this to compress an
image.
(i) Explain how the compression software will compress the image file.
Use an algorithm
to remove repeated/unnecessary data
lossless will not remove data permanently // lossless means original file will be restored
lossy is permanent deletion // lossy means original file will not be restored
Reduce number of pixels // reduce resolution
Decrease colour depth
Describe two ways Hamish can help prevent unauthorised access to his laptop.
Password
No access without the password // description of strong password // limit attempts to guess // changing it regularly
Limited attempts to get into laptop
before laptop is locked
Firewall
Monitor incoming and outgoing transmissions // Stop unauthorised/unwanted incoming/outgoing transmissions/packets.
Biometrics so Need fingerprint/retina scan
Do not leave laptop logged on/unattended So that other people cannot physical access it
Physical security // keep in locked room So that people cannot physically access the laptop
Explain how encryption helps to protect Hamish’s documents
1 mark per bullet to max 2
Uses an algorithm to
scramble data into cypher text // by example
If it is accessed it cannot be understood
Use of keys to encrypt/decrypt data
The IP address 192.149.119.226 is linked to the website with a URL of https://www.ocr.org.uk
(
a) When https://www.ocr.org.uk is entered into a browser, the website homepage is loaded.
Describe the relationship between the website URL (https://www.ocr.org.uk), the IP address and the webserver.
The website is hosted on a webserver
The website/webserver has an IP address
(Browser) sends URL to DNS
URL has a linked IP
DNS finds IP
If DNS cannot find the IP it passes request to higher DNS and if not found return error
IP address sent back to the browser/computer
(Browser) sends request to IP/webserver
Webserver processes request for the website/webpage
…webserver sends the webpage/file/data to the user
Explain why the TCP/IP model uses layers.
A layer can be removed/changed without affecting any other layers
Each layer has its own purpose // separates the purposes // self-contained so it does not need to consider what the other layers do so it can be programming individually
Individual protocols are each smaller/simpler to manage
Different layers can interface with different hardware
When the laptop is in the kitchen, it has better network performance.
Explain why the laptop’s network performance is lower in the bedroom.
- Wifi signal/bandwidth will be weaker/less because // 5GHz is only short range
- …bedroom further away from WAP than kitchen
- ….to get to bedroom has to go through floor/walls etc.
State two ways Hope could improve the wireless network performance in the bedroom
- Change to 2.4Ghz
- Install a signal booster // another WAP // mesh wifi
- Move WAP closer to the bedroom
- Remove obstructions
- Reduce number of devices connected
- Change channel to one not being used in locality
Explain why Hope’s network uses a peer-to-peer model and not a client-server model.
- No server (required for client-server)
- Computers are directly connected to each other
- Computers are equal
- Computers will have software installed/updated individually
- no central security
- Computers will have their own files
- Less initial cost / maintenance
- Specialist required to setup client-server
- Easier to add new devices
- Lesser need for file sharing
- If any device fails/is removed the remainder can continue
Daniel is a medical researcher trying to find a cure for a disease. He has a team of hundreds of people carrying out medical testing.
Recent developments in Artificial Intelligence (AI) mean that a computer program could do the work of dozens of researchers in a much shorter time. Daniel decides to increase his use of Artificial Intelligence.
Discuss the issues surrounding this decision. Consider the following in your answer:
• ethical issues
• legal issues
• cultural issues
Ethical
• Replacing people with machines leads Loss of jobs
• Community will suffer
• Work will be completed faster
• May find a cure faster
• More reliable calculations
• Save more lives
Legal
• More secure than people seeing personal data
• May be at risk if not backed up
• May be at risk of threats e.g. hackers
• Who is responsible if there is an error
Cultural
• Removal of people from workforce
• Change in demand for skills
• Need people to manage the hardware/software instead of medical expertise
• Skills may be lost
4) A computer records an audio file of someone playing a guitar.
(a) Describe what happens when the computer converts the music into a file.
The height of the wave is measured/sampled (at regular/set intervals)
Turned into/stored as binary
M = 77
Explain how the word MOP will be represented in ASCII.
each character from MOP has its ASCII code stored in the order written
77 79 80 (MOP)
ASCII code converted to 8-bit binary number
What is Domain Name Server made up of?
A Domain Name Service (DNS) is made up of multiple Domain Name servers.
