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Binary, Hexadecimal and Denary, Storage, Compression, Digital Audio,…
Binary, Hexadecimal and Denary
Storage
Primary
RAM
Random Access Memory, holds data and instructions currently being used by the processor. Directly accessible by the processor. All data and instructions are lost when power is turned off
ROM
Read Only Memory, instructions are permanently etched onto a ROM chip. When power is turned off these still remain. Bootstrap loader and instructions to start the OS are held on this ROM chip
Virtual memory
Virtual memory is needed when there is not enough physical RAM to store the open programs. It is held on the hard disk. Programs are transferred to the virtual memory from RAM when they are not currently being executed, and they are transferred back to the RAM from virtual memory when they are needed again
Secondary
Optical storage
A laser creates marks in a pattern on the disk. A laser light detects where the lights are and translates it into a readable format
Capacity 3
Speed 3
Portability 2
Durability 2
Reliability 3
Cost 2
Magnetic storage
Read and write more across the medium and change how magnetised that part of the medium is e.g. one level of magnetism is a 1, the second would be a 0
Capacity 1
Speed 2
Portability 3
Durability 3
Reliability 2
Cost 1
Solid state drive
This is made of microchips (switches). The state of the switches determine if a 1 or a 0 is stored.
Capacity 2
Speed 1
Portability 1
Durability 1
Reliability 1
Cost 3
data storage
Bit, Nibble (4 bits), Byte (8 bits), Kilobyte (1000 Bytes or 1 Kb), Megabyte (1,000 Kb), Gigabyte (1,000 MB), Terabyte (1000 GB), Petabyte (1,000 TB) Honorable Mention: YOTTABYTES (1024 ZB)
Compression
Lossless: This method reduces the file by using an algorithm that compresses data into a form that may be decompressed at a later time without any loss of data returning the file to its exact original form.
Lossy: It is a technique that compresses the file size by discarding some of the data. A substantial amount of data can be discarded before the result is noticeable to the user.
Compression ratio : Original file size / Compressed file size
Digital Audio
Sound exists as waves- however as computers only understand binary files this needs to be converted into such.
Sound created on a computer exists as digital information that is encode as audio files.
Digital sound is broken down into thousands of samples per second- each of these samples is then stored as binary data
Images
Metadata
Metadata is data about data. In other words, metadata describes the structure of the data file. When a media player opens a file it looks for the file type, how many horizontal and vertical pixels there are and the colour depth of the file.
Resolution
The number of pixels we use is known as the resolution
On average, computer screens use 1366x768 pixels which means we can display images using 1,049,088 pixels
Colour depth
Colour depth is how many bits will be used to store the colour for each pixel in the grid
1 bit allows 2 values (black and white)
2 bit allows 4 (4 different colours)
3 bit allows 8
8 bit allows 256
24 bit allows 16,777,216
Types of digital images
BITMAP
the page is divided into an invisible grid and each pixel is assigned a colour
VECTOR
drawn by following a set of mathematical instructions
Example:
-draw a circle
-radius: 6 pixels
-centre: 10,10
-line thickness: 1 pixel
ASCII. ASCII stands for American Standard Code for Information Interchange and was first used so that the computer can understand the characters typed by a human.
Normal ASCII is 7 bits
Extended ASCII is 8 bits
, Extended ASCII was made before Unicode and it supported a few more characters such as the pound symbol and others
Unicode. Unicode was made because the american typing system "ASCII" did not support characters that were not of the English language and other characters. Unicode is 2 to the power of 16 bits and can handle every special letter and most symbols. It is the code that is used today
This is a Solid State Drive
This is a hard disk drive
This is an example of some optical storage
