AQA Computer Science (Paper 2) - Computer System, Computer Networks, Cyber Security

What is computer hardware?

Physical components of a computer system

What are the 2 main types of hardware

internal & external (aka. peripheral devices)

What is internal hardware? + examples

Physical components IN a computer system which help it process info.

Examples: CPU, RAM, motherboard, graphics card, HDD

What is external hardware? + examples

Physical components OUTSIDE or connected to a computer system.

Examples: keyboard, monitor, mouse, USB port, microphone

What is computer software?

Collection of programs, data and instructions that run on a computer

What are the two main types of software?

Systems & application software

What are system softwares & the two types of systems software?

= software that manages hardware & provides platform for application software

2 main types are: operating systems & utility software

What are operating systems & what are their functions?

= collection of programs that manage and control the computer.

Functions: MUMPS - memory management, user interface, multitasking, peripheral management, security!

List some examples of operating systems

iOS, android, windows

What is utility software? (+examples)

= software that helps maintain the computer system

eg. antivirus , encryption, data compression softwares

What is application software (aka. apps)? (+examples)

= software that performs end-user tasks

eg. word processors, web browsers, media players, CAD software

What is a device driver?

= a type of software which enables communication between the operating system and a hardware device

What are the 4 types of logic gates & how do they work?

1. AND Gate: Outputs 1 only if both inputs are 1; otherwise, it outputs 0.

2. OR Gate: Outputs 1 if at least one input is 1; outputs 0 only when all inputs are 0.

3. NOT Gate: Inverts the input; if the input is 1, the output is 0, and vice versa.

4. XOR (Exclusive OR) Gate: Outputs 1 if the inputs are different; outputs 0 if the inputs are the same.

What Boolean operators are used for each logic gate?

• . → AND gate

• + → OR gate

• ⊕ → XOR gate

• Overbar [line above letter] → NOT gate

What are the main difference between low-level and high-level programming languages? (2 points for each + examples)

Low-level (eg: machine code, assembly):

• Closer to machine code

• Less readable and more complex

High-level (eg: Python, Java):

• Closer to human language

• Easier to debug and maintain

What are the differences between machine code and assembly language?

Machine code:

• Consists of binary that the CPU directly executes (doesn’t need to be translated)

• Specific to a type of processor

Assembly code:

• Consists of mnemonics

• Needs an assembler to translate code to machine code (to be processed by CPU)

• Often used to make software for embedded systems

PS: Each assembly language instruction matches a machine code instruction exactly

What are 2 pros and 2 cons of low-level programming languages?

Pros:

• Faster execution

• More detailed control over hardware

Cons:

• Hard to read and write

• Less portable - specific to one processor

What are 2 pros and 2 cons of high-level programming languages?

Pros:

• Easier to read and write

• Have convenient features/libraries to improve development

Cons:

• Less control over hardware (compared to low-level)

• Slower code → abstraction & longer processing time

What is a translator?

Program that translates source code into machine code

What are the 3 types of program translators? (+outline how they work)

• Interpreters - translates code line-by-line

• Compiler - translates all the code in one go

• Assembler - translates assembly code to machine code

What are 2 pros and 2 cons of an interpreter?

Pros:

• Stops when it reaches an error- good for debugging

• Can run on many types of CPU

Cons:

• Slower than compilers

• Doesn’t produce a compiled file - re translates each time program runs

What are 2 pros and a con of a compiler?

Pros:

• Produces an executable program - don’t need to repeat process more than once

• Hides source code from end user - protects intellectual property

Cons:

• Compilation process is quite slow

What are 2 pros and a con of using assemblers?

Pros:

• Exact control over hardware

• Quick & efficient

Con:

• Less portable across different CPUs

What is the CPU + what does it do?

Component that processes data/ instructions and controls the computer system

What are the 5 main components of a central processing unit (CPU)?

• Arithmetic Logic Unit (ALU)

• Control Unit

• Clock

• Register

• Bus

What does the Arithmetic Logic Unit do?

= CPU component that performs the operations on the data

What does the Control Unit do?

= CPU component that control CPU activities

What are registers?

= quick & small stores of data within the CPU

What is a bus + what does it do?

= Collection of wires that data/signals are transmitted through from one component to another

What is the clock + what does it do?

= CPU component that provides timing signals to keep the CPU in sync

What is main memory?

= any form of memory that is directly accessible by the CPU

What are 2 examples of main memory?

RAM (random access memory) & ROM (read only memory)

What are the 2 types of memory? (Outline + examples)

• Volatile memory = loses its data when power is lost - eg. RAM, cache

• Non-volatile memory = retains its data when power is lost - eg. ROM, hard disk

What does the RAM do & why is it needed?

Random access memory (named as it can access/store data from any location within memory)

= volatile main memory that holds data and programs currently in use

• Why it’s needed: quick read/write times so it responds to tasks quickly

What does the ROM do & why is it needed?

Read Only Memory

= non-volatile main memory that stores essential programs & can only be read (not edited)

• Fairly small

What is a cache & why is it needed?

= a type of memory that stores copies of frequently used data

• Faster + lower capacity than RAM

• Why it’s useful: Closer to processor + checked before RAM in ‘fetch’ stage

What is secondary storage?

= any non-volatile storage device not directly connected to the CPU

Why is secondary storage needed?

So that there is non-volatile storage available

What 6 factors should be considered when evaluating types of secondary storage devices? (Name at least 3)

• Capacity

• Cost

• Durability

• Portability

• Reliability

• Speed

What are the 3 main types of secondary storage?

• Solid state

• Optical

• Magnetic

How does optical storage work?

1. A laser burns pits into the disc surface to write binary data (lands = 1s and pits = 0s).

2. The laser shines on the disc & light reflects differently for pits or lands.

3. The drive reads these reflections, converting them into digital data

Give an example of an optical storage device

CD (compact disk)

What are 2 pros and 2 cons of optical storage?

Pros:

• Very portable (easy to transport + compatible)

• Durability (resistant to water/dust)

Cons:

• Small capacity (less than SSDs)

• Fragile (easily scratched/damaged)

How does magnetic storage work?

1. Small areas of the disk’s surface are magnetised (1s) or demagnetised (0s)

2. Read/write head contains electromagnets that can read or alter the magnetic state, for data to be stored/recieved

3. Data stored in tracks on the disk

Give an example of a magnetic storage device

HDD (Hard Disk Drive)

What are 2 pros and 2 cons of magnetic storage?

Pros:

• Large capacity

• Cheap to buy

Cons:

• Not very portable

• Generates lots of noise & heat

How does solid state storage work?

• Consists of digital circuits that retain data and can be changed

• Non-mechanical

Give an example of a solid state device

SSD (solid state drive)

What are 2 pros and 2 cons of solid state storage?

Pros:

• Very fast

• Very reliable

Cons:

• Smaller capacity than magnetic

• Expensive

What is cloud storage?

= where data is stored on multiple servers in a remote location

• servers use magnetic or solid-state storage

What s an embedded system?

= a special purpose computer encapsulated by a larger system

Give 2 examples of embedded & non-embedded systems

• Embedded system: microwave, autopilot of a plane

• Non-embedded system: laptop, phone

What are 3 characteristics of an embedded system?

Tend to:

• Have memory & CPU on same chip (easier to manufacture)

• Has more ROM than RAM (as data doesn’t need to be changed + is cheaper)

• Work in real-time (no delays after taking input, unlike a laptop)

What is a network?

= 2+ devices connected together for communication purposes

What are 2 pros and 2 cons of cloud storage, compared to local storage?

Pros:

• Portable - files accessed from anywhere on internet

• Cost effective for large companies (instead of large local storage software)

Cons:

• Dependence on internet connection

• Slower than local storage

What are 2 pros and 2 cons of having a network?

Pros:

1. File sharing across devices

2. Centralised management of security and updates across devices

Cons:

1. More vulnerable to viruses and hacking

2. Specialists needed for maintenance

What are the 3 types of computer network?

• Personal Area Network (PAN)

• Local Area Network (LAN)

• Wide Area Network (WAN)

What are the characteristics of a PAN?

• For close proximity devices (<10 metres)

• Bluetooth = most commonly used PAN

What are the characteristics of a LAN?

• Has small geographical area (under 1 mile)

• Managed by single person/company

What are the characteristics of a WAN?

• For wide geographical area (over 1 mile)

• Collection of LANs joined together, under collective ownership

• Internet = biggest WAN

What are 2 pros and 2 cons of wireless networks, compared to wired ones?

Pros:

• More portable as location is only limited by range

• Less expensive to setup & add devices

Cons:

• Slower data transfer than wired

• Less secure/safe than wired

What are the 3 most common LAN topologies?

• Star

• Bus

• Ring (not on spec)

What is a bus topology + how does it work?

= All devices are connected on a single ‘bus’ cable, terminated at each end (stops signal bouncing back)

• At each device: 1) Listens to electrical signals. 2) checking data packets for specific address. 3) Ignoring data packets it doesn’t recognise

What are 2 pros and 2 cons of a bus topology?

Pros:

• Easy and cheap to set up (only 1 cable is required)

• Doesn’t rely on any other network hardware (eg. Central hub)

Cons:

• Prone to data collisions

• If cable breaks, whole network is affected

What is a star topology?

= all devices are connected to a central switch/hub

What are 2 pros and 2 cons of a star topology?

Pros:

• Network can still work even if single cable stops working

• High speed + most efficient topology

Cons:

• If central switch stops working, entire topology fails

• High maintenance costs

What is cyber security?

= involves safeguarding systems and data from attacks, damage, and unauthorized access

What is social engineering?

= manipulating people into sharing confidential information or performing actions that compromise security

What are the 3 main types of social engineering?

1. Phishing

2. Shouldering

3. Blagging

What is phishing?

= fraudulently obtaining private info, often via email or SMS

What is shouldering?

= observing someone’s private info over their shoulder

• eg. at an ATM

What is blagging?

= tricking someone into giving private information by pretending to be someone trustworthy

What is pharming?

= a cyber attack intended to redirect a website’s traffic to another, fake site

What is malware?

(Malicious code) = code intended to cause undesired effects, security breaches or damage to a system

What are the 4 main types of malware?

• Computer virus

• Trojan horse

• Adware

• Spyware

What is a computer virus?

= piece of code able to copy itself and have a detrimental effect

What is a trojan horse?

= malware that hides within seemingly harmless programs

What is adware?

= malware that presents unwanted ads on a computer (pop up ads)

What is spyware?

= malware installed onto a computer to collect personal information or monitor internet browsing

What are 3 ways to reduce risk of malware?

1. Read software license agreements before installing

2. Update anti virus software regularly

3. Don’t open email attachments from people you don‘t know

What is penetration testing + what is it used for?

= security assessment where professionals simulate cyber attacks to identify vulnerabilities

What are the 2 main types of penetration testing?

• Malicious insider: tester simulates attack from inside and has knowledge of basic system credentials

• External attack: tester simulates attack from outside with no knowledge of system credentials

What are 4 security risks?

• Weak passwords

• Misconfigured access rights (incorrectly set permissions)

• Removable media (physical storage devices)

• Outdated software (not updated to fix security flaws)

What are some security measures to prevent cyber security threats?

• Biometric measures

• Passwords

• CAPTCHA

• Email confirmations (to confirm identity)

• Automatic software updates

What is a database?

= A structured, persistent collection of data

What are the 2 types of databases?

Flat file databases & relational databases