Paper 1 Exam Questions

Question 1

Compare the use of ASCII and Extended ASCII to represent characters

Answer 1

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)

Question 2

Answer 2

Question 3

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.

Answer 3

 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)

Question 4

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

Answer 4

 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

Question 5

(ii) Explain why computers represent data in binary form.

Answer 5

 Computers consist of transistors / switches / logic circuits / gates which only have two values / on or off / 1 or 0 / open or closed

Question 6

Explain the advantages of lossy compression

Answer 6

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

Question 7

Explain the disadvantages of using lossy compression

Answer 7

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

Question 8

Remember

Answer 8

• 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

Question 9

Remember

Answer 9

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)

Question 10

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.

Answer 10

 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

Question 11

Describe how a character set is used to represent the string value stored in the variable “name”

Answer 11

• 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

Question 12

Give two reasons why computer scientists use hexadecimal to represent numbers instead of binary

Answer 12

• Easier/quicker to communicate / enter / write / read / remember
• Less chance of input errors
• They are shorter
• Easy to convert between binary and Hexadecimal

Question 13

(a) State what is meant by the term image resolution[1]

Answer 13

5 a)

• Number of pixels (in an image)

OR

• Height and width (of an image)

Question 14

(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]

Answer 14

• 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

Question 15

(c) Give two ways that the file size of the image could be reduced.[2]

Answer 15

• Reduce number of pixels / resolution
• Reduce number of colours
• Use lossy compression
• Use lossless compression

Question 16

What is the role of switch

Answer 16

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.

Question 17

What is NIC

Answer 17

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.

Question 18

What is a IP address?

Answer 18

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.

Question 19

What is a transmission media

Answer 19

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

Question 20

Compare wireless and wired connections

Answer 20

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.

Question 21

William can choose between a full or incremental backup.

• *Identify the backup method William should use to backup the computer, justifying your**
• *choice.**

Answer 21

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

Question 22

(c) (i) Describe the purpose of the router in the house’s network.

Answer 22

 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

Question 23

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

Answer 23

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

Question 24

The CPU has a clock speed of 3.8 GHz.
Describe what is meant by a clock speed of 3.8 GHz.

Answer 24

 The number of FDE cycles run per given time/second // the frequency that the clock ‘ticks’

 3.8 billion cycles/instructions per second

Question 25

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.

Answer 25

 **Software may be designe**d to **run on 1 core** and **not multiple cores**  **Clock speed also affects speed**  **RAM size also affects speed**  **Cache size also affects speed**

Question 26

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.**

Answer 26

 **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**

Question 27

Explain why it would be beneficial for Alicia to get more RAM instead of relying on virtual memory.

Answer 27

 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**

Question 28

What is the difference between IMAP and SMTP

Answer 28

**IMAP**  **Retrieves/accesses/downloads** (a copy of an) e-mail  **Allows synchronisation/management of account** **SMTP**:  **Sends/forwards/transmits e-mail**

Question 29

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.

Answer 29

 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**

Question 30

Describe two ways Hamish can help prevent unauthorised access to his laptop.

Answer 30

 **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**

Question 31

Explain how encryption helps to protect Hamish’s documents

Answer 31

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**

Question 32

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.

Answer 32

 The website **is hosted on a webserver**  The **website/webserver has an IP address**  (Browser) **sends URL to DNS**  U**RL 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 r**equest to IP/webserver**  Webserver **processes request for the website/webpage**  …webserver **sends the webpage/file/data to the user**

Question 33

Explain why the TCP/IP model uses layers.

Answer 33

 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**

Question 34

When the laptop is in the kitchen, it has better network performance. Explain why the laptop’s network performance is lower in the bedroom.

Answer 34

* Wifi signal/**bandwidth will be weaker**/l**ess because** // **5GHz is only short range** * …**bedroom further away from WAP than kitchen** * ….**to get to bedroom has to go through floor/walls etc.**

Question 35

State two ways Hope could improve the wireless network performance in the bedroom

Answer 35

* **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**

Question 36

Explain why Hope’s network uses a peer-to-peer model and not a client-server model.

Answer 36

* **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

Question 37

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

Answer 37

_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**

Question 38

Answer 38

Question 39

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.

Answer 39

 The **height of the wave is measured/sampled** (at regular/set intervals)  **Turned into/stored as binary**

Question 40

M = 77 Explain how the word MOP will be represented in ASCII.

Answer 40

 each c**haracter from MOP has its ASCII code stored in the order written**  **77 79 80 (**MOP)  A**SCII code converted to 8-bit binary number**

Question 41

What is Domain Name Server made up of?

Answer 41

A Domain Name Service (DNS) is made up of multiple Domain Name servers.