A set of problem-solving methods involving
understanding the problem, developing possible
solutions and presenting them in a way a
computer can understand
Decomposition
Breaking down a complex problem
into smaller more manageable parts
Pattern Recognition
Looking for similarities/ trends
in and among problems
Abstraction
Focussing only on important
information and removing
unnecessary details
Algorithm
Developing a step-by-step solution to
the problem, or the rules to follow to
solve the problem.
Code
The implementation of
an algorithm in a
programming
language
Searching Algorithm
A set of instructions to
conduct a search for data
Sorting Algorithm
A set of instructions to
put data in order
Binary Search
A method of searching
which involves a data set
being halved at each step
Linear Searching
A method of searching
involving moving from
one item to the next in
sequence
Bubble Sort
A method of sorting involving
repeatedly passing through a list,
comparing, and swapping items in
the wrong order
Micro:bit
A pocket sized computer that
can be programmed
Programming
Designing and building an
executable computer program
Sequencing
Carrying out instructions
one after the other
Selection
A decision, or a question,
that affects the output
of the program
Iteration
The repetition of steps,
often referred to as a
'loop'
Variable
An identifier for a storage location in
memory which contains a value that
can be changed (stores data in a computer program)
Data Types
Character (single character)
Real (decimal number)
Integer (whole numbers)
Boolean (true/false, yes/no)
String (more than 1 character)
Networks
LANs
A LAN is a network that is geographically confined to one
building or site. Examples include networks employed by
small businesses, small organisations, schools, colleges,
universities and in homes.
Connecting to a LAN: WIFI (It uses radio
waves to connect computers to the LAN)
and Ethernet Cables (A specification that
enables computers to communicate with
each other).
WANs
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.
Organisations that have more than one office or branch,
such as banks, tend to use a WAN. The WAN allows the
head office to communicate and share data with the
sub-offices and branches. Communication is done through
national telephone infrastructures or via wireless
transmission. Each office or branch has its own LAN that is
connected together using the WAN.
Connecting to a WAN: Modems/ Routers,
telephone connection, mobile data
(GPRS) or cable/satellite
WPANs
Wireless Personal Area Network, It allows us
to pair devices over a small range. You can use
bluetooth to connect to WPAN. Examples
include connecting to Bluetooth speakers
through a smartphone.
A network is two or more computers (or
other electronic devices) that are connected
together for the purpose of communication.
They are connected by a wired medium such
as cables, or by a wireless medium such as
Wi-Fi.
Advantages:
- File sharing = Users can share files with other users
- Hardware sharing = Users can share hardware, such as printers
- 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
LARGER NETWORKS:
- 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
- User monitoring - Network managers can monitor what users do on a network
- Levels of access = Different users can be given different access rights. This gives network managers
the ability to generally restrict user access to certain files, while granting permission to specific users
Disadvantages:
- Cost = Additional equipment is needed to allow computers to communicate
- Management = Networks require management by technical staff such as 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
NETWORK HARDWARE
COMPONENTS
Network Interface Card (NIC)
A printed circuit board
or card that is installed
in a computer so that it
can be connected to a
LAN
Router
A device for connecting devices together to form a
network. It connects all devices to the modem by
giving them an internal IP adress.
Routers are one of the most commonly used connection devices.
They are used to send data signals across the internet. Routers
work by collecting knowledge of available routes to transmit data.
They then determine the most suitable route for sending data.
Routers are also commonly used in homes. These types of router
usually contain a hub and a WAP, enabling a small peer-to-peer
network to be formed. Additionally, they contain a modem, which
allows users to connect to the internet.
Modem
Stands for modulator/ demodulator. Sends/receives data
between computers over telephone circuits, It converts the
digital signals from the computer into audio tones for
transmission over ordinary telephone lines and converts
incoming audio signals into digital signals for the computer.
Normally, they are built into free routers given out by Internet
Service Providers (ISP)
Hub
A hub is a small device that allows wired devices to connect to a
network. Hubs have no knowledge of the devices connected.
Any signal (traffic) that arrives at the hub is transmitted to all
connected computers. This affects network performance as
many unnecessary signals are transmitted across its
connections
Wireless Adapter
A printed circuit board with a built in
transmitter/receiver for sending signals so that it can
be connected to a LAN
Switches
Switches are similar to hubs, with one
important difference - a switch records
which computers are connected to which
ports. When traffic is received, the switch
forwards the traffic to its intended
recipient only. This improves network
performance by cutting down on
unnecessary transmissions.
Security Measures:
- Firewalls: It controls which program/ software may
send/receive data packets from computer/networks.
It also stops unauthorised/untrusted users from
accessing your computer system and only
authorised/trusted programs are allowed to
send/receive data packets. Useful for keeping
whatever comes from the internet and into our
computer system secure; also makes sure that any
dangerous malware doesn’t intrude over our activity.
- Anti-Malware Software - It scans your computer system
regularly to check if there’s any malware installed - then it
moves it to the side (quarantines it) and doesn’t delete it -
instead it asks permission from the user to delete it from your
computer system. To be safe, you need to install an
anti-malware software to scan the downloads and
attachments that you receive. It also needs to be updated
regularly to keep up with the latest threats. Thus, malware
deletes, corrupts or cleans.
- Encryption - It encrypts (scrambles) data packets using a
cipher so that unauthorised users can not read it. A key is
needed to decrypt (unscramble) the data packets in order
to be read. The recipients (websites) need to have a
‘’https://’’ at the start of the URL to make sure that data
packets are encrypted. Also WiFi connection should be
encrypted to stop users accessing your network
- Passwords - Passwords are basically a barrier
between unauthorised users accessing your
data and then your actual data. That barrier is
you making a good password. A good password
includes lower and upper case letters
(alphanumeric). It may also include numbers
and symbols ( , . / ; @).
Network Threats
Phishing
A cybercrime in which a target/s are
contacted by email, telephone or text
message by someone posing as a
legitimate institution to lure individuals
into providing sensitive data such as
personally identifiable information,
banking and credit card details and
passwords
Hackers
Unauthorised access to our
private information without
accord anonymously
Trojan Horses
Pretending to be a
trusted website/app
when in reality, it's a type
of malware causing harm
to a computer system
Zombies
It's a computer connected to a
network that has been
compromised by a hacker, a virus
or a Trojan. It can be used
remotely for malicious
Viruses
It's a type of computer program
that when executed, replicated
itself by modifying other
computer programs infecting
them. (they need a host program)
Spyware
It is a malicious software which
installed in a users OS, it can spy
and record phone calls, have access
to messages, photos and personal
information like important
documents etc.
Adware
It's a malicious software that
automatically displays or downloads
advertising material such as banners
or pop-ups when a user is online and
when clicked, it steals personal data
Connection Types + Adv & Disadv
- WiFi: Advantages: Good for connecting
to portable devices like smartphones
etc. Disadvantages: Slower data
transfer that Ethernet, can be hacked
and has a small range
- Ethernet: Advantages: Faster data
transfer than WiFi (100 meter range)
Disadvantages: The cables can be more
expensive than a WiFi connection
- Bluetooth: Advantages: 7 devices
can be connected at once.
Disadvantages: range is short and can
be hacked
- GPRS: Advantages: Good for mobile
devices and can be used on the move.
Disadvantages: It's expensive (requires SIM
card), connection is slower in some areas
Computer Hardware
CPU
The purpose of a CPU is to process data using
the Fetch, Decode, Execute cycle. - It's the cycle
that the CPU follows from boot-up until the
computer is shut down in order to process
instructions. It firstly fetches data packets from
the RAM, the the CPU itself makes sense of it
and tries to 'decode' it and then gets executed
(sent away to the output devices e.g.monitor)
Clock Speed
The clock speed measures the number of fetch, decode, execute cycles in the CPU
executed per second. Measured in GHz
The higher the clock speed, the more instructions can be
executed per second so the performance of the computer
will be improved and programs and data will load faster.
Cores
Cores are small CPUs or processors built into a big CPU or
CPU socket. It can independently perform or process all
computational tasks simultaneously.
If there are more cores, more programs will be opened at
the same time which will mean t hat the CPU will execute
more instructions every second so the computer's
performance will be improved
Dual core means 2 independent
processors. Quad core means 4
independent preocessors
Cache
Cache is a storage hardware that allows to
help websites, browsers and apps load faster.
A cache makes it easy to quickly retrieve data,
which in turn helps devices run faster
Cache memory stores frequently-used instructions. Cache memory is
faster and more expensive than RAM. If there is a larger amount of
cache memory storage, a greater number of frequently-used
instructions can be stored. This means that programs will load faster
which also means that more instructions can be accessed quickly,
which will improve the performance of the computer
RAM
It's purpose is to store the programs/apps/ parts of the OS and
data files we are currently using. It is volatile, meaning that the
data is not stored when t he computer system is switched off.
Virtual Memory
Virtual memory is used when there is insufficient
RAM to open the programs and files. Virtual
memory is stored on the secondary storage
If you upgrade it to more RAM, this means that you don’t have to use virtual
memory as much. This is an advantage because RAM is also faster at
accessing data than virtual memory. Disadvantage: virtual memory is slower
to access data compared to RAM. This will make loading programs slower
compared to using RAM
The greater the amount of RAM, the more instructions and data can be stored and
processed while a program is running which will also mean that more programs can be
opened at the same time. This means that less instructions will be stored in the much slower
virtual memory and will therefore improve the performance of the computer and you won't
need to rely on virtual memory as much.
Secondary Storage
Optical Storage
Is any storage method in which data is written and
read with a laser. CDs, DVDs and Blu-Ray are examples
of this type of storage.
Advantages: Cost effective and very portable
Disadvantages: Not very durable and has a
limited capacity
Magnetic Storage
Data is stored by magnetising the
surface of flat, circular plates called
platters. These platters rotate at a
very high speed.
Advantages: Cost effective due to having a larger
capacity than solid state.
Disadvantages: Not as durable due to moving parts and
reads/writes data slower in comparison to solid state.
Solid State Storage
Uses microchips to store data
instead of magnetised disks and
do not contain any moving
parts.
Advantages: More durable and can read and
write data much faster than magnetic storage.
It is also more energy efficient.
Disadvantages: Less cost effective in comparison to
magnetic because it has a much smaller capacity. It also has
a limited read/write lifespan.
Embedded Systems
Embedded systems are computers built into other devices. They are often
used as control systems - they monitor and control machinery. They are
dedicated systems which means that they are designed for a single task. A
they are dedicated to a single task, they are much easier to design, cheaper
to produce and more efficient at doing their task.
Washing Machine:
The embedded system in a washing machine will:
- Control the water pumps so that they do not overflow
- Control the water release mechanisms
- Control the washing powder tray release
- Lock the washing machine door until washing cycle has finished
- Control the temperature for the different wash cycles
Increment
When a variable increases in
value (e.g. score increments
by 100)
Decrement
When a score decreases in
value (e.g. libes decrements
by 1)
Flowchart
An algorithm which is a visual
representation of the steps needed
to solve a problem
- Input/Output = This shows
something that is going in our
out the system
- Terminator= This either
contains START or END
- Process= This shows
something that is happening
- Decision = We use these when we need
to make a choice. Decisions must have
two exits. YES and NO
- Connector= Shows the
direction of data
through the flowchart
Pseudocode
An algorithm which uses
text to show the steps
needed to solve a problem
Data Representation
Bit
A single 1 or 0
Nibble
4 bits
Byte
8 bits
Kilobyte
1024 bytes
Megabyte
1024 Kilobytes
Gigabyte
1024 Megabytes
Terabyte
1024 Gigabytes
Binary
A number system that contains two symbols, 0
and 1. Also known as base 2. All information
that is processed by a computer is in the form
of a sequence of 1s and 0s. Therefore, all data
that we want a computer to process needs to
be converted unto binary
Base 2
The binary counting system
uses 2 symbols - 0 and 1
Denary/Decimal
The number system most
commonly used by people. It
contains 10 unique digits 0 to 9.
Also known as decimal or base 10
Base 10
The denary counting system
uses 10 symbols - 0 to 9
ASCII
A 7-bit character set used
for representing English
keyboard characters
UNICODE
A 16-bit character set. Is
capable of representing 65,536
different and a much wider
range of characters
Binary Addition
Binary Addition Rules
0+0=0
1+0=1
1+1 = 0 (carry the 1)
1+1+1 = 1 (carry the 1)
Binary addition is a simple mathematical operation used
to add two binary numbers together. It involves adding
two or more binary numbers together.
Overflow error
Sometimes, when adding up two binary numbers
we can end up with an extra digit that doesn't
fit. This is called an overflow error.
An overflow error occurs when the
largest number that a CPU register
can hold is exceeded
Images
Pixel
A single point in an image
Resolution
The number of pixels that make up
an image e.g. 800x600
Colour Depth
The number of bits used to store each
pixel is called the colour depth. Images
with more colours need more pixels to
store each available colour. This means
that images that use lots of colours are
stored in larger files. E.g. 8 bit colour and
24 bit 'True Colour'
Image Quality
Image quality is affected by the resolution of the image. The resolution of an
image is a way of describing how tightly packed pixels are. In a low-resolution
image, the pixels are larger so fewer are needed to fill the space. This results in
images that look blocky or pixelated. An image with a high resolution has more
pixels, so it looks a lot better when you zoom in or stretch it. The downside of
having more pixels is that the file size will be bigger, taking more storage space.
Images also need to be converted into binary in order for
a computer to process them so that they can be seen on
our screen.. Digital images are made up of pixels. Each
pixel in an image is made up of binary numbers. If we say
that 1 is black (or on) and 0 is white (or off), then a
simple black and white picture can be created using
binary. To create the picture, a grid can be set out and
the squares coloured (1 - black and = - white). But before
the grid can be created, the size needs to be known. This
data is called metadata and computers need metadata to
know the size of an image. If the metadata for the image
to be created is 10x10, this means the picture will be 10
pixels across and 10 pixels down
00 - white
01 - blue
10 - green
11 - red
1 bit per pixel (0 or 1):two possible colours
2 bits per pixel (00 or 11): four possible colours
3 bits per pixel (000 or 111): eight possible colours
4 bits per pixel (0000 or 1111): 16 possible colours
DPI
Dots per inch; number of
individual dots that can be
placed in a line within the span
of an inch