Computer science Flashcards
What is the purpose of an operating system
To manage hardware and run software
What are the functions of an operating system
communicate with input and output devices through drivers
provides a user interface
manage system security and user accounts
organise CPU and its processing tasks
What are some ethical issues of technology
some people don’t have enough money to buy smartphone- barred from opportunities
each country has a different level of tech- people in countries of lower tech will be barred from some opportunities
internet grants anonymity-causes anti-social behaviour
What are some legal issues of the internet
malware can be used to steal info from users and then sell that info without there permission
identity theft is more common
Pirating
What are the pros of using compilers
translates the whole source code and the creates an executable file
only needed once to create an executable file
what are the cons of using a compiler
compiling takes a long time
What are the pro’s of using a interpreter
will return first error it finds- good for debugging
What are the cons of using an interpreter
needed every time you want to run the program
program will run more slowly-code being translated as program is running
doesn’t create an executable file after one use-translates and runs code one line at a time
What are the pros of using high-level language
easier for humans to write and understand
what are the cons of high level language
it has to be translated into machine code for computer to understand
What are the pros of low level language
easier for machines to understand
what are the cons of low level language
harder for humans to understand
What is an SMTP
simple mail transfer protocol- used to send and transfer emails
What is a HTTPS
a version of HTTP that secures data
what is HTTP
hyper text transfer protocol-used by web browsers to access websites and communicate with websites
What is FTP
File transfer protocol- access edit and move files to another server/device
What is a relational database
a database with multiple tables that are linked.
Reduces the amount of times data repeats and data that don’t match
What are some examples of data compression methods
Run length encoding
Huffman coding
What is White box penetration
To simulate an attack from a malicious insider, who have knowledge of basic credentials example username and password.
What is a penetration test
A penetration test is a simulated cyberattack carried by ethical hackers to find vulnerabilities in a system, website, mobile application, or network
What does wan stand for
Wide area network
What does WAN stand for
Wide area network
What does LAN stand for
Local area network
What does PAN stand for
Personal area network
What is in a PAN network
blue tooth devices
What is Rom
ROM is a non volatile primary storage
What does non volatile mean
when the computer is turned off the stored items will still be kept
What is ROM used for
to store instructions and data that the computer needs to run
What is cloud storage
remotely accessed storage which is accessed through the internet
Adv of cloud storage
you can access your files from any location that has connection to the internet
reduced need to make backups as the cloud already makes backups
Disadv of cloud storage
cloud storage hosts could be targeted by hackers
people have less control over their data
access to data is only possible with an internet connection - no connection means no access to data
What is the formula for calculating pixels
resolution X colour depth
what is the formula for calculating sounds
length X sample rate X bytes
What is sample resolution
the number of bits per sample
What is Abstraction
a technique that removes the unnecessary details so that you can focus on the important parts of a question
What is decomposition
When you break down a large problem into smaller manageable steps
What is selection
Selection is where a piece of code is only run if a condition is met
What is Iteration
Iteration is the repeated execution of a section of code when a program is running.
What is algorithmic thinking
a way of solving problems by producing algorithms
What are sort algorithms
a set of instructions used to arrange a data set into a particular order
What does Boolean represent
True or false
basically just one of two values
What are the factors that affect CPU speed
clock speed
Cache size
Cache type
how many cores the CPU has
What is Secondary storage
Storage that is directly connected to the CPU
Why is Secondary storage needed
Needed so there is long term storage is available
How is data stored in an optical disk
Binary data is stored as variations of height on the disks surface
How is data read on Optical storage
Light is shined on the disk and is reflected back differently when it either hits a flat piece of the disk (land) or a divot in the disk.
The way the light reflects back decides if the value will either be read as a one or a zero
What are the pros of optical storage
it is fairly reliable and durable
and has good portability
What are the cons of optical storage
can be easily damaged through scratches
Has a small capacity usually less than a GB
How does magnetic storage work
As the disk is spinning, a read/write head containing electro magnets moves across its surface. To write data, the head magnetizes or demagnetizes a section of the disk that is spinning under it. To read data, the head makes a note of whether the section is magnetized or not.
parts of the surface is either magnetized (1) or demagnetized (0) the heads control this and read what state they are in
What are the pros of magnetic storage
Large capacity
Cheap
What are the cons of Magnetic storage
Not that durable
Generally not that portable
can be noisy and generate heat
What is solid state storage
Solid state storage is a special type of storage made from silicon microchips. It can be written to and overwritten like RAM. However, unlike RAM, it is non-volatile, which means that when the computer’s power is switched off, solid state storage will retain its contents.
What are the cons of SSD’s
Expensive
Generally have a smaller capacity than magnetic
What are the pros of SSD’s
Very fast storage- because the data is stored electrically in silicon chips called cells.
Very reliable as they’re non-mechanical
Don’t need defragmentation
Are silent
What is an Embedded system
A special purpose computer encapsulated in a larger computer
What are the qualities of embedded systems
Can only perform a specific task
Can not be easily programmed
What are some examples of embedded systems
Cockpits in a plane
Systems such as braking systems in a car
Embedded systems in hospital devices
What is a bus
a collection of wires through data is transmitted
Why is the width of a bus important
The the width of a bus is how many bits it can transfer at a time
What is the purpose of the address bus
Sends a memory address along the CPU to the main memory.
To fetch/write data the CPU needs
to tell the ram where the Data is through the address of the data
What is the purpose of the data bus
A data bus sends the actual data to and from the memory
What is the purpose of the control bus
Control bus carries commands from the CPU and status messages from other hardware devices.
What is the ALU
The circuit that performs the operations on the data
What is the control unit
The circuits coordinating the activities of the CPU
What are registers
Quick small stores of data within the cpu
what is the purpose of the control unit
The control unit controls the flow of data. It also keeps track of memory addresses of the instruction each cycle
What is the purpose of the ALU
The ALU gets data from the registers and CU, performs an operation on it, and sends the output back to the registers
What is the purpose of the registers
The registers hold any data, instructions and memory addresses that are about to be used by the CPU. There are specific registers for different tasks, E.G. one that holds data that is about to be used by the CPU
What is the purpose of the clock
The clock sends out a signal that constantly cycles between one and zero - which is used to synchronize when instructions will be carried out
What is cache
Very fast memory in the CPU. It’s slower than the registers but faster than Ram
The bigger its cache, the less time a processor has to wait for instructions to be fetched.
What is the purpose of Cache
Stores regularly used data so that the CPU can access it quickly the next time its needed
What is the Purpose of ROM
The purpose of ROM is to hold the instructions needed for a computer to properly boot up
What does the CPU do with the ROM when the computer boots up
The CPU reads instructions from the ROM telling it to perform self checks and setup the computer
What is the purpose of RAM
Ram is where all data, Files and programs are stored while there being used - for example when a computer boots up the operating system is moved from secondary storage to RAM as its quicker.
What are graphical user interfaces
GUIs feature a desktop where everything is displayed. Applications run in Windows, and all objects (apps, hardware and files) are represented by icons.
Application features are accessible through the use of menus.
Users interact with the interface by using a mouse and on-screen pointer.
What are the pros of graphical user interfaces
GUIs are powerful and easy to use
What are the cons of graphical user interfaces
require a lot of processing power.
What are mobile user interfaces
Mobile UIs are similar in many ways to GUIs, except that they respond to touch.
What are command-line interfaces
Command line interfaces are text-based. Users control the computer by typing in commands.
What are the pros of command line interfaces
CLIs require little processing power and are extremely powerful
What are the cons of command line interfaces
they are difficult to use
What does multi tasking mean
Multitasking means to be able to run more than one program simultaneously
What must a computer have to be able to multi- task
the operating system can support multitasking
the computer has enough memory to hold more than one program in primary memory at the same time
What are device drivers
Software that controls and communicates with peripherals
What are the advantages of device drivers
any device can be used with the operating system, as long as a driver is available for it
drivers can be updated, usually to give better performance or to remove a bug
What are cores in a CPU
A processing unit within a CPU is known as a core. Each core is capable of fetching, decoding and executing its own instructions.
The more cores a CPU has, the greater the number of instructions it can process in a given space of time.
What is clock speed
Clock speed is the number of pulses the central processing unit’s (CPU) clock generates per second. It is measured in hertz.
What is over clocking
CPU clocks can sometimes be sped up slightly by the user. This process is known as overclocking.
The more pulses per second, the more fetch-decode-execute cycles that can be performed and the more instructions that are processed in a given space of time.
What are the cons of over clocking
Overclocking can cause long term damage to the CPU as it is working harder and producing more heat.
What are the key elements of von-Neuman architecture
data and instructions are both stored as binary.
data and instructions are both stored in main memory.
instructions are fetched from memory one at a time and in order - serially.
the processor decodes and executes an instruction, before cycling around to fetch the next instruction.
the cycle continues until no more instructions are available.
What is von-Neuman architecture
A description of the processing architecture that all CPUs use. John von Neumann invented the processor architecture which stores a program in memory as instructions and executes them sequentially using the ALU, control unit and registers. This is known as the stored program concept.
What five registers does a processor based on von-Neuman architecture have
Program counter (PC) - holds the memory address of the next instruction to be fetched from main memory.
Memory address register (MAR) - holds the address of the current instruction that is to be fetched from memory, or the address in memory to which data is to be transferred.
Memory buffer register (MBR) - holds the contents found at the address held in the MAR, or data which is to be transferred to main memory. It is also referred to as the memory data register (MDR).
Current instruction register (CIR) - holds the instruction that is currently being decoded and executed.
Accumulator (ACC) - holds the data being processed and the results of processing.
What is a network topology
A network’s topology is the arrangement, or pattern, in which all nodes on a network are connected together.
What are the most common topologies
bus topologies
star topologies
What are bus topologies
A network layout where all nodes are connected along a linear link/backbone known as a bus.
What are star topologies
A network where each node is connected to a central switch.
What is a node
Any device connected to a network.
disadvantages of using a bus topology
the whole network fails if the backbone cable is broken
terminators must be installed at each end of the backbone
having one backbone increases the chances of data collision
Advantages of using a bus topology
it is easy to connect nodes to the network
less cabling is needed compared to a star topology, making it cheaper to install
Advantages of using a star topology
each node is separately connected, therefore a failure of one node or its link - transmission media - does not affect any other nodes
new nodes can be added to the network simply by connecting them to the switch
star networks tend to have higher performance as a message is passed on to its intended node only
Disadvantages of using a star topology
the whole network fails if the switch fails as no node can communicate
a wired star topology requires plenty of cable - in a large network this can be expensive
What are the four layers in an network
Application layer
Transport layer
Network layer
Data link layer
What operates at the application layer
applications such as web browsers and email programs operate at this layer. Protocols such as HTTP, HTTPS, SMTP, IMAP and FTP operate at this layer.
What operates happens at the transport layer
this breaks down the message into small chunks (packets). Each packet is given a packet number and the total number of packets. This layer sets up the communication between hosts, using protocols such as TCP and UDP.
What happens at the network layer
this adds the sender’s and recipient’s IP addresses to the packet, and packages the data to make it ready for transmission. The network layer also routes the packets across the network.
What is at the data link layer
the network interface card/controller (NIC) and operating system drivers are at this layer.
Advantages of using networks
file sharing - users can share files with other users
hardware sharing - users can share hardware, such as a printer
communication - users can communicate via email, chat, or by video
roaming access - users can sign in to any computer on the network and be able to access their files
centralised maintenance and updates - network managers can apply software updates across a network, removing the need for a user to worry about having to do so
centralised security - anti-virus software and firewalls can be implemented across a network, helping to protect user files from risks
user monitoring - network managers can monitor what users do on a network
levels of access - different users can be given different access rights, and this gives network managers the ability to generally restrict user access to certain files, while granting permission to specific users
Disadvantages of networks
cost - additional equipment is needed to allow computers to communicate
management - networks require management by technical staff such as a network manager
spread of malware - viruses and other forms of malware can easily spread across an improperly secured network
hacking - once a device is connected to another device, it is possible that data may be accessed without the device owner’s permission
What is LAN
A local area network (LAN) is a network that is geographically confined to one building or site. Examples include networks employed by small businesses, small organizations, schools, colleges, universities and in homes.
What are WAN’s
A wide area network (WAN) is a network that is spread over a wide geographical area. It can cover more than one site, or be spread across a country, or even the world.
What are PAN’s
A personal area network (PAN) is a network that is spread over a very small area. It often covers no more than a few metres and is used to connect personal devices such as a smartphone and wireless headphones or a laptop.
