GCSE Computer Science Unit 1 - Revision

CPU - Components

CPU Number of cores – how does it affect performance? Processor speed – what is the negative for increased speed? Cache memory – where located? Reduced Instruction Set Computer (RISC) and Complex Instruction Set Computer (CISC). Compare speed and chance of overheating.

Computer Memory Permanent Volatile Data can be changed Speed   Permanent Volatile Data can be changed Speed Cache memory   ROM  RAM  Flash memory 

Secondary Storage Flash drive Solid State Drive (SSD) - could be in computer. Faster, less power consumption. Magnetic Tape (back up networks) Magnetic – hard drive, tape Optical – CD, DVD, etc. Cloud storage

HCI – User interface Graphical User Interface – WIMP, Menu Driven Command Line Voice Touch Screen

Binary How many bits are in a byte? What are the largest and smallest denary values that can be made using 8 bit binary? Convert 57 to 8 bit binary. Convert 00111010 to denary.

Hex What base is hexadecimal? Convert 179 to hexadecimal. Convert 2D to denary. Convert E3 to binary. Convert 10100011 to hex. Why is hex used by technicians rather than binary?

Characters, Images, Sound Compare ASCII and Unicode. Explain the advantages of Unicode compared to ASCII. If an image is 10 pixels wide by 40 tall, and it is black and white, state the file size in bytes. What affect does adding colour have to the file size? State three items of metadata. What does increasing the sample rate of the sound have on quality and file size?

Instructions Opcode - instruction Operand – value or memory location of value

Logic Gates AND – both input must be 1 for output of 1 NOT – reverses input, e.g. 1 becomes 0 OR – either input must be 1 for output of 1 Complete the truth table below A NOT A B NOT A AND B 1

Data Types String ‘hello world’ Real – 34.23 Integer - 78 Character – ‘s’ Boolean - True/False

Data Types State the most appropriate data types for the following fields. Name – ‘Daniel James’ Year – 10 Form – ‘B’ Form Tutor – ‘Mr Smith’ Computer Science Effort Grade (A-E) – ‘A’ Average Test Mark – 78.66 Resit paper? – No Student Ref – ‘bish1034’

Disk Organisation File transfer Formatting Compressing System restore De-frag Control Panel Virus Protection Firewall

Operating System Peripherals Printing Backing storage Compression De-fragmentation RAM Processes / Software Security

Defrag tool, Virus checker What is the disadvantage of a fragmented disk? Explain the process of defragging the disk. State three functions of a virus checker.

Application Software State an example of use for School awards evening: Word processor Database Spreadsheet Drawing package Presentation software

IP and MAC address What is an IP address? An IP address (Internet Protocol address) is the unique identification number given to every device that is connected to the internet.  It represents the unique location on which you are connected to the internet, allowing devices all over the world to communicate with each other. If you take your laptop to McDonalds and connect to the internet, the IP address will differ from when you connected to the internet in Starbucks.  This is because the location you are using to connect to the internet has changed. An IP address may look like: 62.102.245.31

IP and MAC address What is a MAC address? A MAC address (Media Access Control address) is a unique number that identifies the actual device that is connected to the internet or network. A MAC address does not change when you connect to the internet from different locations, it is part of the network interface card (NIC) inside your device. A MAC address is made up of 48 bits, shown as 6 groups of hexadecimal digits. A MAC address may look like: 00 12 0E A6 B0 68

IP and MAC addresses What is the difference between an IP and MAC address?

DNS – Domain Name System Server https://www.youtube.com/watch?v=2ZUxoi7YNgs Explain the steps involved when entering a web address (e.g. www.google.co.uk)

Networks State 3 topologies Data collisions speed, reliability, adding extra workstations, cost. Compare a star and ring topology. State 3 advantages of a LAN compared to stand alone computers. State 3 disadvantages of a LAN. Draw and label the different topologies.

Packet Switching / routing For transferring data on network. Files are split into packets to be sent on network. They may follow different routes (routing table) but eventually reach destination. Then re-assembled and viewed.

Networks Packets of data (Source address, destination address, data, checksum, how to reassemble, tracking info)

Protocols / rules Send/receive data TCP/IP – Transmission Control, Internet Protocol FTP – File Transfer HTTP – Hypertext Transfer Protocol

Security Access Levels Passwords (strength, brute force attack) Encryption Acceptable Use Policy Disaster Recovery Backup Archiving

File types / compression Provide examples of the following file types: Html Jpeg Mp3 Fla Png Lossy / Lossless compression

Programming Errors Provide examples of the following Truncation Rounding Logic Syntax Run time

Programming State two advantages of using libraries. What is the difference between global and local variables? What is a constant?

Libraries Already tested Quicker to enter code Less code, easier to manage Random numbers, time, etc.

Programming State all outputs if the user enters 5: Output “Y9 Maths Data” Input X If X > 5 Then output “Pass” Else output “Fail” End if If X > 3 Then output “You do not need to resit” Else output “Resit required”

Software development environment - facilities Editor Compiler Interpreter Linker (for libraries) Loader Debugger Trace Variable watch Break point Memory inspector Error diagnostics

Compilers & Interpreters Convert high level code to machine code. Interpreter – one line at a time, every time code is run. Compiler – all lines are converted once, does not require conversion on next run, unless code amended. Compilers Lexical – comments and spaces removed Syntax – syntax errors identified Semantic – suitable data types for variables Code generation – machine code generated.

Legislation Data Protection Act Protects individuals who have details stored by various organisations. Number of rules that must be followed. State 3 rules of the DPA. State 3 organisations that store data about individuals. Computer Misuse Act Hackers & Viruses Copyright Act Illegal downloads