Computer Science GCSE Exam Practice

William is creating a film for a school project using a digital video camera. (a) The digital video camera has a secondary storage device. (i) Explain why the digital video camera needs secondary storage.

• For long term/permanent/non-volatile storage // storing when the device is turned off.To store the videos / data / files. .For transferring the videos (to another device)

• For short term/permanent/volatile storage // not storing when the device is turned off  Not for transferring the videos (to another device)

The digital video camera uses solid state storage. Explain why solid state storage is the most appropriate type of storage for the digital video camera.

• Portable  Lightweight - device needs to be carried - Small physical size can fit in a small camera. Durable - No moving parts device is moved so may be dropped // won’t be damaged when moving around

• Fast access/read/write speed the device will retrieve the videos without delay Efficient power consumption run on battery // longer battery life

• Reliable needs to work when out in the ‘field’. Sufficient/large capacity Videos are large file size // store more videos.

• All of the above

William transfers the videos to a computer for editing. (i) The computer has 1GB of storage free. Calculate the number of videos that could be stored on the computer if each video was 100MB in size. Show your working

• 1000/10 = 100 videos

• 1000/100 = 10 videos

A program needs to calculate the size of files in bytes. The program must: ○ Ask the user to input a file size in megabytes ○ calculate and output the number of bytes this represents in a user friendly format (e.g. "There are 5242880 bytes in 5MB"). Write an algorithm using pseudocode to calculate the number of bytes in a given number of megabytes.

• output "Please enter the file size in megabytes"

  input numberMB

  numberKB = numberMB * 1024 (or 1000)

  numberBytes = numberKB * 1024 (or 1000)

  output "There are " & numberBytes & " bytes in " & numberMB & "MB"

• Output asking for file size (in megabytes) 

  Taking number of MB as input 

  Multiplying by 1024 or 1000 

  Multiplying by 1024 or 1000 (may be same line as bullet 3, this must be the final value with no further changes) 

  Outputting the final bytes value in an appropriate message

• output "Please enter the file size in megabytes"

  input numberKB

  numberKB = numberMB * 1024 (or 1000)

  numberBytes = numberKB * 1024 (or 1000)

  output "There are " & numberBytes & " bytes in " & numberMB & "MB"

• All of the above

William’s computer has utility programs installed including automatic backup. (i) William can choose between a full or incremental backup. Identify the backup method William should use to backup the computer, justifying your choice.

Method:

Justification:

• 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 

  Safer as have more past versions to revert to 

  User may have changed settings on computer

  Faster to restore the backup

  Needs to do a full before he can do an incremental

• All of the above

William wants to upload his videos on the Internet and is considering releasing them under a Creative Commons license. Explain how a Creative Commons license will impact the use of William’s videos by other people

• Allows free distribution // other people can use/edit his work  Other people can redistribute his work

• Can choose to restrict other people to be able to use/edit/share the videos  Work is still copyrighted // others cannot claim it as their own 

  No-derivative  …William can set that if others edit it they cannot redistribute it with the edits  attribution

• …Can insist e.g. on having his name on it if re-used // referencing // must be credited  Can insist on non-commercial use // others cannot sell/profit from his work // personal use only

  

• All of the above

When connecting computers into a network, the use of appropriate protocols are important. (a) Explain what is meant by a protocol.

• HTTPS / hyper text transfer protocol secure  Encrypts the connection/data // Uses SSL/secure socket layer

• An agreement / set of rules / standard  …for how computers should communicate // how data is sent/received/transmitted on a network  Example of what could be agreed in the protocol (e.g. speed / error checking / etc.)

• FTP / file transfer protocol  Uses a client-server model // sends from client to server // sends from server to client

For each of the scenarios below, identify the most appropriate protocol to be used and explain the function of the protocol. (i) A user wants to transfer a file directly from his computer to his friend’s computer

• HTTPS / hyper text transfer protocol secure  Encrypts the connection/data // Uses SSL/secure socket layer

• An agreement / set of rules / standard  …for how computers should communicate // how data is sent/received/transmitted on a network  Example of what could be agreed in the protocol (e.g. speed / error checking / etc.)

• FTP / file transfer protocol  Uses a client-server model // sends from client to server // sends from server to client

For each of the scenarios below, identify the most appropriate protocol to be used and explain the function of the protocol.

[2] (ii) A customer wants to securely log into her bank’s website to check her account balance

• An agreement / set of rules / standard  …for how computers should communicate // how data is sent/received/transmitted on a network  Example of what could be agreed in the protocol (e.g. speed / error checking / etc.)

• FTP / file transfer protocol  Uses a client-server model // sends from client to server // sends from server to client

• HTTPS / hyper text transfer protocol secure  Encrypts the connection/data // Uses SSL/secure socket layer

Explain the difference between how the IMAP (Internet message access protocol) and SMTP (simple mail transfer protocol) protocols are used.

• IMAP  Retrieves/accesses/downloads (a copy of an) e-mail  Allows synchronisation/management of account

  
  

  SMTP:  Sends/forwards/transmits e-mail

• IMAP  retrieves files

  
  

  SMTP:  is used by HTTP