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2.2.1 understand how computers encode characters using 7-bit ASCII -…
2.2.1 understand how computers encode characters using 7-bit
ASCII
UNICODE
In Unicode there are 155,063 characters with code points, covering 168 modern and historical scripts, as well as multiple symbol sets.
his article includes the 1,062 characters in the Multilingual European Character Set 2 (MES-2) subset, and some additional related characters.
Unicode is a standard for encoding text that supports a vast number of characters from different writing systems, including modern and historical scripts, symbols, and emojis.
Extended ASCII
Extended version known as Extended ASCII uses an additional bit, making it an 8-bit system.
Making it 256 unique characters providing additional characters, symbols, and special characters beyond 128
Extended ASCII includes characters used in various languages, such as accented letters and additional symbols, making it more versatile for international use.
However, it is important to note that Extended ASCII is not a single standard but a collection of various encoding schemes that assign different characters to the range of 128–255
ASCII
American Standard Code for Information Interchange,
7-Bit character code
Today, ASCII has been largely replaced by Unicode, which also includes ASCII encodings. In fact, ASCII encoding can be considered technically obsolete. However, the first 128 characters of the Unicode Transformation Format 8 (UTF-8) use the same encoding as ASCII, making ASCII text and UTF-8 compatible.
The reason the characters are encoded as 7-bit values is because early computers handled data in bytes — blocks of 8 bits. The extra, eighth bit was originally reserved for error checking. Computers can only process numbers, so text characters need to represented by numbers too.
ASCII based Languages
Python
C
Java
Practical Use and Limitation
ASCII is still widely used in modern computing for text files, communication protocols, and other applications that require a small, fixed set of characters.
Unicode includes the first 128 characters of ASCII and extends to support over a million characters, ensuring compatibility with a wide range of languages and symbols
In summary...
ASCII uses a 7-bit binary code to represent characters, allowing for 128 unique characters. The extended version, Extended ASCII, uses an 8-bit system, providing 256 unique characters. Despite its limitations, ASCII remains a foundational standard in digital communication.
ASCII characters are represented by 7-bit binary numbers, with each character having a unique binary code ranging from 0000000 (0 in decimal) to 1111111 (127 in decimal). These codes are used to store, process, and transmit text data in computer systems and across various communication protocols.
2.2.2 understand how bitmap images are represented in binary
(pixels, resolution, colour depth)
Bitmapped graphics are stored as binary.
A bit mapped graphic is a 2D array of pixels. The total number of pixels in an image is known as the resolution, and the number of colours that can be used is determined by the bit depth.
BITMAPS AND VECTORS
The attributes are used by the computer to create the graphic. Rather than storing the data for each pixel, the computer will generate an object by looking at its attributes.
VECTORS graphics are stored as a list of attributes.
Key points:
Vector Maps are stored as a list of attributes
Vector graphics are resolution independent, meaning scaling is possible without loss in quality
Resolution independence can make best use of high-resolution output device
Generally, file size is smaller than that of bit mapped images unless the graphic contains lots of layers or many complex objects
SVG (Scalable Vector Graphics) is a common file format used for vector graphics
The number of bits used for each pixel is called the color depth
Difference between Vectors and Bitmaps
Bitmap images are made up of pixels, while vector files are made up of lines described by equations.
Bitmap images become grainy when zoomed in, while vector images stay smooth and sharp.
Vector images can be scaled without losing resolution, making them more versatile.
Resolution
The fineness of detail that can be seen in an image - the higher the resolution of an image, the more detail it holds. In computing terms, resolution is measured in dots per inch (dpi).
Pixel
Picture element - a single dot of colour in a digital bitmap image or on a computer screen.
The more pixels per inch on the screen, the higher the resolution of the picture.
However the higher the image resolution, the more number (No. of bits) is needed to stored the graphics
Binary, Denary and Hexidecimal
Binary
0-1 (Off and on)
A binary number is a number expressed in the base-2 numeral system or binary numeral system, a method for representing numbers that uses only two symbols for the natural numbers: typically "0" (zero) and "1" (one). A binary number may also refer to a rational number that has a finite representation in the binary numeral system, that is, the quotient of an integer by a power of two.
The simplest way a computer can read and understand it's knowledge
Arithmetic in binary
0 + 0 → 0
0 + 1 → 1
1 + 0 → 1
1 + 1 → 0, carry 1
Hexi decimal
A 16 based numerical system that starts from 0-15
0 0000
1 0001
2 0010
3 0011
4 0100
5 0101
6 0110
7 0111
8 1000
9 1001
A 1010
B 1011
C 1100
D 1101
E 1110
F 1111
Purpose
Memory addressing
MAC addresses
Debugging and Memory dumps
color code in web design
Denary
Definition: Denary, also known as "decimal" or "base 10," is the standard number system used around the world. It uses ten digits (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9) to represent all numbers.
It's 10 because we start counting from 0
64 is the biggest place value that can be subtracted from 84. Place a 1 in the 64 place value column and subtract 64 from 84, which gives 20. 16 is the biggest place value that can be subtracted from 20. Place a 1 in the 16 place value column and subtract 16 from 20, which gives 4.
Humans use denary because it's easier to read and use
2.3.1 understand that data storage is measured in binary multiples (bit, nibble, byte, kibibyte, mebibyte, gibibyte, file sizes and data capacity requirements tebibyte) and be able to construct expressions to calculate
Bit = smallest unit of data
Nibble = 4bits
Byte = 8 bits (A single character)
Kibibyte = 2^10 bytes
Megabyte
Gibibyte
Countering Expressions
Text file :Expression: (Bytes per character) × (Number of characters)2
Image file :Expression: Width × Height × Colour depth
Sound File :Expression: Sample rate × Bit depth × Duration × Number of channels
2.3.2 understand the need for data compression and methods of
compressing data (lossless, lossy)
