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Paper 1, Paper 1 pt 2, Paper 1 pt 5, Paper 1 pt 4, Paper 1 pt 3 - Coggle…
Paper 1
1.2.3 Units of storage
Bit
The smallest unit of storage. Holds only a 1 or 0.
Byte
A collection of 8 bits. Can be used to represent a number up to 255.
Nibble
A collection of 4 bits. Can be used to represent a number up to 15.
Kilobyte
A collection of 1024 Bytes.
Megabyte
A collection of 1024 kilobytes.
Gigabyte
A collection of 1024 Megabytes.
Terabyte
A collection of 1024 gigabytes.
Petabyte
A collection of 1024 Terabytes.
1.2.2 Storage
Secondary storage
Secondary storage is needed to keep programs and data indefinitely. Secondary storage is non-volatile
Magnetic storage
Magnetic storage or magnetic recording is the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory.
Optic storage
Optical storage is the storage of data on an optically readable medium. Data is recorded by making marks in a pattern that can be read back with the aid of light, usually a beam of laser light precisely focused on a spinning optical disc.
CD, DVD, Blu-Ray
Not robust and expensive for large amounts of data
Solid state storage
Solid-state storage is a type of computer storage media that stores data electronically and has no moving parts.
Includes USB, SSD, SDHC
Holds data using electronic switches. Open switch = 1
Very portable, but expensive
Storage is a process through which digital data is saved within a data storage device by means of computing technology. Storage is a mechanism that enables a computer to retain data, either temporarily or permanently.
1.2.1 Memory
RAM
Volatile Memory
Measured in GB (gigabytes)
It stores the information your computer is actively using so that it can be accessed quickly. The more programs your system is running, the more memory you'll need.
ROM
Read only memory (ROM) provides permanent storage for instructions needed during bootstrapping, or the process of turning on the computer.
Non-Volatile data stays where it is when a computer loses power
Virtual memory
Used once RAM is full - Volatile - Can be accessed from the CPU directly
Volatile memory
Stored on the computers hard disk
It is much slower than RAM
Flash memory
Non volatile - Expensive - Limited times it can be used - Fast - Used as portable memory
Faster than Hard disk slower than RAM
1.2.4 Data storage
charactors
computers represent everything in 1's and 0's
The 3 ways of displaying data
ASCII
8 bits
leftmost bit is a check digit
127 possible characters
extended ASCII
8 bit (1 byte)
256 possible characters
unicode
2 byte
65,000+ possible characters
all world languages
images
An image is a picture that has been created or copied and stored in electronic form.
Colour Depth
Many images need to use colours. To add colour, more bits are required for each pixel. The number of bits determinates the range of colours.
Resolution
Image quality is affected by the resolution. The resolution is a way of describing how tightly packed pixels are.
Metadata
Metadata tells the computer system the resolution and Colour Depth
numbers
binary
its a number system that only uses two digits
1's and 0's
Binary to Denary
128, 64, 32, 16, 8, 4, 2, 1
Example:
15 in binary is:
0 0 0 0 1 1 1 1
binary shift
To multiply a number, a binary shift moves all the digits in the binary number along to the left and fills the gaps after the shift with 0: to multiply by two, all digits shift one place to the left. to multiply by four, all digits shift two places to the left.
Hexadecimal
A base 16 system used to simplify binary
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
Video on how to convert Hex to Denary
Hex conversions
Example
12 is 1100 in binary and C in hex
It is a 4 bit number so you would do
(1x8) + (1x4) + (0x2) + (0x1) = 12
sound
computers understand sound in anologue
anologue to digiatal converter will capture a sound wave at regular time intervals
this is known as a sample
bitrate
a measure of how much data is proccessed for each second of sound
bit rate is calculated by:
sample rate X bit depth
bit depth
refers to the number of bits used t record each sample
the higher the bit depth, the more accuratley a sound can be recorded
sample rate
the number of samples recorded in any given period of time
the higher the sample rate, the closer the recorded signal is to the origanal.
sample rate is measured in hertz
The alpitude (hieght of the sound wave represents volume
The higher the alplitude the higher the volume of the sound
audio files also have metadata
1.2.5 Compression
lossy
some data is removed
images are compressed by reducing colour depth
Examples
JPEG
MEPEG
lossless
no data is lost
we use this compresion with:
text files
spreadsheets
financial records
emails
it does not make the file size that much smaller
Examples that use lossless compression
PDF
GIF
It makes a file size smaller
Paper 1 pt 2
Components of the CPU
The Control Unit (CU)
The control unit controls and monitors communications between the hardware attached to the computer.
The Arithmetic Logic Unit (ALU)
The Arithmetic Logic Unit (ALU) is a digital circuit used to perform arithmetic and logic operations.
The Registers
Registers are small amounts of high-speed memory contained within the CPU.
The Cache
The Cache is a small amount of memory which is a part of the CPU - closer to the CPU than RAM. It is used to temporarily hold instructions and data that the CPU is likely to reuse.
The Clock
A computer's processor clock speed determines how quickly the central processing unit (CPU) can retrieve and interpret instructions.
Data Buses
A data bus is a system within a computer or device, consisting of a connector or set of wires, that provides transportation for data.
Von Neumann
Von Neumann Architecture
Von Neumann architecture is the design upon which many general purpose computers are based. The key elements of von Neumann architecture are:
Data and instructions are both stored as binary digits
Data and instructions are both stored in primary storage
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
John Von Neumann Facts
John Von Neumann Facts
Name: John Von Neumann
Date of Birth: December 28, 1903
Date of Death: February 8, 1957
Place of Birth: Budapest, Hungary
What is the CPU?
The CPU is the Central Processing Unit which is the brains of the computer.
The CPU enables your computer to interact with all of the applications and programs installed.
Paper 1 pt 5
Topologies
Star topologies
A star topology connects nodes trough a central hub
Advantages
Causes less data collisions
More secure than mesh
Harder to access information
Disadvantages
Slower than mesh
Everything goes through a central hub
Mesh topologies
Every node is connected to each other
Advantages
As there is no central node if a node goes down the network will still be able to run
It is also quicker as data can be transferred directly from node to node without having to go through a central hub
Most reliable
Disadvantages
More expensive than a star topologie
Data collisions are more common
Node
A node is a device on a network e.g. Laptops or Desktop computers
Paper 1 pt 4
Threats and prevention
Threats
Malwear
DDoS
Poor Network policy
Phishing
People as weak points
SQL Injections
Brute Force Attacks
Prevention
Anti-virus software
Secure passwords
Encryption
Firewalls
Access Levels
Identifying vulnerabilities
penetration testing
When a system is tested for vulnerabilities to reveal weaknesses
Network policy
A policy that provides rules and guidelines on what users can do
Paper 1 pt 3
