Paper 1 Flashcards
Fetch-decode-execute Cycle
Instructions are fetched one by one from main memory, decoded, and then executed by the processor. This cycle repeats until the program is
complete
CPU (Central Processing Unit)
A chip within the computer which controls the operation of all parts of the computer and decodes then executes program instructions.
ALU (Arithmetic Logic Unit)
The part of the CPU responsible for arithmetic and logical operations.
Processor Cache
High speed memory built into the CPU. Instructions are copied to cache memory allowing them to be accessed more quickly and therefore increasing the speed of the CPU.
Register
A small area of memory within the CPU where data is stored temporarily to avoid the delay in copying to and from main memory,
Von Neumann Architecture
The design on which most computers are based. It defines several registers along with the fetch-execute cycle and how the CPU interacts with main memory.
MAR (Memory Address
Register)
A register. It contains the address of the instruction currently being read from or written to main memory.
MDR (Memory Data Register)
A register. It contains the instruction which has just been copied from main memory.
Program Counter
A register. It contains the address of the next instruction to be fetched from memory. It is updated each time a new instruction is fetched to contain the address of the next needed instruction.
Accumulator
A register. Stores the result of the last operation.
Clock Speed
How many instruction cycles the CPU can deal with in a second. Measured in MHz or GHz. Faster is better.
Cache Size
The larger the amount of cache the CPU has the more instructions it can store without having to transfer to main memory and therefore the faster it will perform.
Cores
Some CPUs have more than one core, each containing its own ALU and registers and therefore capable of carrying out instructions independently. The more cores, the more instructions the CPU can process at once and therefore the faster it performs.
Embedded System
Specialist hardware and software build into a device with a single specific
purpose. They are usually found within appliances such as washing machines.
Primary Storage
Also known as memory. Holds the data, programs and instructions currently in use.
RAM
Random Access Memory. Stores programs and data before they are processed by the CPU. Read/write memory, meaning the contents can be changed. The contents are lost when the computer is turned off.
ROM
Read Only Memory. Data can be retrieved but not changed and the contents are not lost when the computer is turned off. Used to store programs for embedded system
Volatile Memory
Data stored in volatile memory is lost when the computer is turned off.
No-Volatile Memory
Data stored in non-volatile memory is not lost when the computer is turned off.
Virtual Memory
Space on the computer’s hard drive used as main memory (RAM). Virtual memory is slower than main memory.
Optical Storage
A type of secondary storage which stores data on a spinning plastic or metal disk. Data is read from and written to the disk using a laser.
Magnetic Storage
A type of secondary storage which uses magnetic fields to store data. A read/write head reads and writes data from the media.
Solid State Storage
A type of secondary storage which uses flash memory to store data. They have no moving parts and are much faster than optical or magnetic storage.
HDD (Hard Disk Drive)
A magnetic storage drive which can store large amounts of data and is often the main method of secondary storage in personal computers. The drive contains a number of internal disks and a read/write head used to read and write data.
DVD (Digital Versatile Disk)
A high capacity optical storage disk commonly used for video storage. A range of capacities are available up to 17GB
CD (Compact Disk)
An optical storage disk often used to store music. Capacity is usually around 800mb
SSD (Solid State Drive)
A solid state storage drive which carries out the function of a traditional HDD. They are much faster than HDDs and less easy to damage as they have no moving parts. They are also more expensive and usually lower capacity.
Bit
The smallest unit of storage, containing a binary 1 or 0.
Nibble
4 bits (half a byte)
Byte
8 bits
Kilobyte (KB)
1000 bytes
Megabyte (MB)
1000 KB
Gigabyte (GB)
1000MB
Terabyte (TB)
1000GB
Petabyte (PB)
1000TB
Binary
A number system used by computers. It contains only two symbols, 0 and 1 and is also known as base 2.
Denary
The number system most often used by people. It uses the digits 0 to 9 and is also known as base 10 or decimal.
Positive Number
A number greater than 0.
Negative Number
A number less than 0.
Integer
A whole number without a decimal point or fraction. E.g. 1, 100 or 88122
Overflow Error
This happens when not enough space has been allocated to store the results of a calculation. For example, if one byte has been allocated but the result is 9 bits long.
Hexadecimal
A number system used by computers. It contains only two symbols, 0 and 1 and is also known as base 2.
Binary Shift
A process used to preform maths on binary numbers. It involves moving all the digits to the left or right.
Most Significant Bit
The furthest left digit in a string of binary numbers, its position means it has the highest value.
Least Significant Bit
The furthest right digit in a string of binary numbers, its position means it has the lowest value.
Character
A single symbol, for example a letter, number or punctuation mark.
Character Set
A system for representing characters in binary, each character is assigned a unique binary number.
ASCII
American Standard Code for Information Interchange. A 7 bit character set used to represent characters.
Unicode
A much larger character set created to overcome the limited number of characters available in ASCII. It includes many different language
characters as well as other symbols such emojis.
Pixel
Short for Picture Element. Pictures on a computer are divided into a grid, with each square in the grid being one pixel which can be a single colour.
Metadata
Additional data about a file such as when it was created or who created it. Commonly used with photos to store things like the make of camera or location the photo was taken.
Colour Depth
The amount of bits available for colours in an image. The higher the colour depth the more colours available and therefore the more realistic the image will appear.
Resolution
The number of pixels an image is divided into. The higher the resolution, the more pixels in the image and the clearer it will be.
Sample Rate
The number of samples taken in one second. This is measured in hertz (Hz), 1Hz is one sample per second. The higher the sample rate, the more samples per second and therefore the higher the quality of the file.
Bit Depth
The number of bits available for each sample. The higher the bit depth, the more bits available and therefore the better the quality.
Analogue
A continuously varying signal, usually represented as a curved line. Examples include sound or temperature recordings.
Compression
A way of reducing the size of a file. It is often used with photos, music and video files.
Lossy Compression
A compression method which reduces the file size by removing certain data. The original file cannot be restored from the compressed version but the file is reduced by more than with lossless compression.
Lossless Compression
A compression method which reduces the file size without losing any data. The original file can be restored from the compressed version, but the file size is not reduced by as much.
Network
Two or more computers connected together for the purposes of sharing data or resources.
LAN (Local Area Network)
A network which covers a small geographic area such as a single building.
WAN (Wide Area Network)
A network which covers a large geographic area.
Client - Server
A network setup where resources or processing are carried out by a
central computer (called a server) with other devices (called clients) accessing resources via the network.
Peer to Peer
A network setup where all computers have an equal status and function as both client and server.
Wireless Access Point
Uses a wireless radio to allow devices to connect wirelessly to an existing network.
Router
A device which connects two or more different networks together allowing them to communicate with one another.
Switch
A device which provides computers and other devices with a wired connection to a network.
NIC (Network Interface Card)
A component within a computer or other device which allow it to connect to a network. The card provides the physical connection to the network and controls the sending and receiving of data between the computer and the network. It may be built into the computer motherboard or a separate
expansion card.
Transmission Media
The physical connection which carries data between network devices. This could be a cable or wireless signals depending on the network.
DNS (Domain Name System)
A system which links a URL or other human readable name with an IP address.
Hosting
The storing of files or other data on a server. The server storing the data is called the host.
The Cloud
A term for accessing storage or other resources remotely across The Internet.
Web Server
A server which hosts web sites and pages for users to access, usually via The Internet.
Network Topology
The way in which computers and other network devices are connected together.
Star Network
A network topology where all devices connect back to a single central point. All communications travel via the central point.
Mesh Network
A network topology where all devices are connected to each other rather than a central point.
Bandwidth
The amount of data which can be transferred via a network in any given
time. More bandwidth allows more data to travel across the network at the same time resulting in faster transfer speeds.
The Internet
A global network connecting millions of computers and other devices.
URL
Uniform Resource Locator. A human readable name given to websites
and other Internet resources. DNS is used to translate the URL into the IP of the web server.
Client
A computer or other device which accesses data from a central server.
Ethernet
A physical copper cable used to connect devices on a network. The term also refers to the protocols and standards used to control how data is
sent and received on the cable.
Wi-Fi
A technology which uses wireless signals to connect network devices.
Bluetooth
A short range wireless networking technology. It has relatively low range and speeds and is most often used for peripheral devices such as mice
or headsets.
Encryption
The process of converting data so that it cannot be easily read or understood without first being decrypted. It is often used to keep important data secure when sharing it over a network.
IP Address
Stands for Internet Protocol Address. A unique address assigned to every computer on a network.
IPv4
Internet Protocol Version 4. Devices are assigned addresses made up of four numbers separated by dots, e.g. 232.112.11.1 each number can be
between 0 and 255.
IPv6
Internet Protocol Version 6. Designed in response to the limited number of addresses in IPv4. Devices are assigned an address made of eight groups of hexadecimal characters such as
FE80:CD00:0000:0CDE:1257:0000:211E:729C
MAC Address
Media Access Control Address. A 12 digit hexadecimal number assigned to a network interface card. Each card has its own unique MAC addressed assigned when the card is made.
Standard
An agreed way of doing something allowing different people and organisations to make products and services which work together.
Protocol
An agreed set of rules for how network communications should take place.
TCP/IP
Transfer Control Protocol / Internet Protocol. A group of standards which control how data is sent and received over networks including the
Internet.
HTTP
Hypertext Transfer Protocol. A standard for transferring web pages between a client and web server. It is based around the idea that clients send a request which the server responds to.
HTTPS
Hypertext Transfer Protocol Secure. A version of the HTTP standard with security added. Commonly used for accessing secure websites such as online banking.
FTP
File Transfer Protocol. A standard for file transfer over networks.
POP
Post Office Protocol. A standard used by email clients to retrieve emails from an email server.
IMAP
Internet Message Access Protocol. A standard used by email clients to access emails stored on an email server. It has the advantage over POP
of allowing emails to be stored and organised on the mail server.
SMTP
Simple Message Transfer Protocol. A standard used for the sending of emails over networks and The Internet.
Malware
A term for any software which is designed with malicious intent. Malware may damage the computer, monitor user activity and files or delete or damage data. There are many different types of malware which behave in different ways.
Social Engineering
Attempting to gain access to computer systems by targeting the people using the system instead of using technical measures to attack the system itself. People are often the weakest security point in a computer system and examples such as watching someone enter their password or pretending to be their boss and telling them to do something urgently aim
to take advantage of this fact.
Phishing
Attempting to trick someone in to revealing information such as their password, financial, or other private information by pretending to be someone else. Phishing usually takes place by email, and involves sending an email which pretends to have come from the user’s bank or
other trusted organisation or person.
Brute-force attack
Attempting to guess a code or password by trying every possible solution until the correct one is found. The attack may work through a list of
common passwords or dictionary words, or simply start with a code of 0000, followed by 0001 etc.
Denial of Service Attack
Attempting to send more traffic or data to a computer system than it is able to handle. If successful, this results in parts of the system, or even
the whole system, being unable to process the data is receiving and failing.
Data Interception
Attempting to access data whilst it is being transferred between devices, usually over a network. The victim usually has no idea that their data has been stolen, and the attacker may access usernames and passwords or
whole files.
SQL Injection
Entering SQL code into a data input field on a web site or application. If the system is not correctly coded, and uses a SQL database, the code could be run directly on the database, allowing the attacker to access,
change or delete the entire database.
Penetration Testing
An authorised hacking attempt where a person or company attempts to hack into a system or network and then reports their finding to the system’s owner. This allows security flaws to be fixed before real hackers
can take advantage of them.
Anti-Malware Software
Software which attempts to detect, prevent and remove malware on a computer system. Anti-Virus software is a common example of anti-
malware software.
Firewall
A network security device which checks traffic passing through it against a set of rules, only traffic which meets the rules is allowed through. This prevents traffic from unauthorised devices or using unauthorised
protocols from passing through.
User Access Level
Controlling which aspects of a system or network users can access. Users are allowed access only to the parts of the system the need, preventing them from accidentally or deliberately damaging sensitive parts of the system or accessing sensitive data.
Password
A secret word or phrase, usually provided alongside a username, to control access to a system or network. Only someone who knows the correct password can access the system.
Encryption
The process of converting data so that it cannot be easily read or
understood without first being decrypted. It is often used to keep important data secure when sharing it over a network.
Physical Security
Securing the physical components of a system or network. This could be
as simple as locking a portable computer to a desk or advanced as storing servers in a reinforced building with multiple locked doors.
Operating System (OS)
Controls the operation of all aspects of the computer and provides an interface by which a user can interact with the computer.
User Interface
A part of the operating system or other software which allows the user to interact with and control it. They usually comprise of a graphical component which the user can see on a monitor or other display hardware, and way for the user to interact with the system, either by
typing commands, or clicking items with a mouse or touchscreen.
Memory Management
The function of the Operating System which manages the computer’s memory, controlling how the memory is used and which applications can access it.
Multitasking
The ability for an operating system to run more than one task or application at the same time.
Peripheral Management
The ability of an operating system to control and manage hardware devices such as printers, mice or speakers which are connected to the
computer.
Device Driver
Computer code which provides instructions for how the operating system should interact with a specific piece of hardware. Device drivers are specific to the operating system and piece of hardware for which they
were designed.
User Management
A function of the operating system which manages user accounts. In many cases, multiple user accounts can exist with their own username, password and access rights allowing more than one person to use the
same computer.
File Management
A function of the operating system which manages files and folders stored on either the computer’s internal storage, or external storage devices such as a USB Stick.
Access Rights
A function of the operating system which manages the access that different users and applications have to the system. It allows different user accounts or applications to be granted access to different parts of
the system.
Encryption Software
Software which encrypts data. The encryption process turns the data into code which is only readable with the correct key. This is designed to keep the data secure and prevent it being read by those who should not have access to it.
Defragmentation
Software which reorders files stored on a hard disk so that they run in a sensible order to improve performance and efficiency.
Data Compression
Software which compresses data so that it takes up less storage space.
Ethical
The idea of right and wrong by which people should behave. This is not the same as what is legal or illegal, but the idea of always doing the right thing.
Legal
A set of rules which lay out behaviours which are not allowed and the
punishments for breaking these rules. Laws vary from country to country, with new laws being made and existing ones being updated.
Cultural
A set of behaviours and expectations which people accept as being normal and expected within their daily lives. These are not enforced by any laws, and don’t always have to do with right and wrong, but are how people expect things should be. An example might be colouring a delete
button red, or ordering items starting at the top left of the screen.
Environmental
Matters relating to the natural world around us and making sure we take
good care of things like animals, the atmosphere and the planet as a whole.
Privacy
The expectation that certain information is kept secret. Usually this relates to personal information such as someone’s address or medical
history which they would not want to be shared.
The Data Protection Act (2018)
A law in the United Kingdom which governs the processing of personal data. It outlines the requirements for organisations who handle data and the rights of those who provide the data.
Computer Misuse Act (1990)
A law in the United Kingdom which makes misuse of computer systems illegal if certain criteria are met.
Copyright Designs and
Patents Act (1998)
A law in the United Kingdom which provides protection in law for works and materials. The act explains what protections are available, and what (if any) steps need to be taken to register for these protections.
Software License
The right for an organisation or user to use a piece of computer software. The license is an agreement between the person or organisation who made the software and those using it and lays out any rules or
restrictions associated with use. The user may have to pay either a one time or yearly fee for the license.
Open Source Software
Software where the code is made available to the public to view or edit as they wish. Open source software is usually free for anyone to use.
Proprietary Software
Software where the source code is owned by a person or organisation and is not available to the public.
Describe each stage of the Fetch-decode-execute Cycle (there are 7)
- The memory address held in the program counter is copied into the MAR.
- The address in the program counter is then incremented (increased) by one. The program counter now holds the address of the next instruction to be fetched.
- The processor sends a signal along the address bus to the memory address held in the MAR.
- The instruction/data held in that memory address is sent along the data bus to the MDR.
- The instruction/data held in the MDR is copied into the CIR.
- The instruction/data held in the CIR is decoded and then executed. Results of processing are stored in the ACC.
- The cycle then returns to step one.
Compare the Capacity of Optical, Magnetic and Solid State memory
Optical Storage (CD, DVD, Blu-ray) Low
Magnetic Storage (HDD) High
Solid-State Storage (SSD, USB, SD card) Medium to High
Compare the Speed of Optical, Magnetic and Solid State memory
Optical Storage Slow (due to laser reading data)
Magnetic Storage Moderate (moving parts slow access)
Solid-State Storage Very Fast (no moving parts)
Compare the Portability of Optical, Magnetic and Solid State memory
Optical Storage Good (lightweight, but needs a drive)
Magnetic Storage Poor (bulky, mostly internal)
Solid-State Storage Excellent (lightweight and compact)
Compare the Durability of Optical, Magnetic and Solid State memory
Optical Storage Poor (easily scratched/damaged)
Magnetic Storage Moderate (mechanical parts can fail)
Solid-State Storage High (shock-resistant, no moving parts)
Compare the Reliability of Optical, Magnetic and Solid State memory
Optical Storage Low (prone to scratches and wear)
Magnetic Storage Moderate (degrades over time)
Solid-State Storage High (long lifespan, minimal wear)
Compare the Cost of Optical, Magnetic and Solid State memory
Optical Storage Very Cheap (per GB)
Magnetic Storage Cheap (per GB)
Solid-State Storage Expensive (per GB)
What is the equation for sound file size
sound file size = sample rate x duration (s) x bit depth
What is the equation for image file size
image file size = colour depth x image height (px) x image width (px)
What is the equation for text file size
text file size = bits per character x number of characters
