Text - ASCII & Unicode
Computers process text by changing it into binary code. There are different standards for this translation:
ASCII - American standard code for information interchange, 127 different characters are represented using 7-bits. It contains the english alphabet, numbers, and a set of symbols.
Unicode - An extension to ASCII. Unicode 2 has 256^2 different characters. Over time they extended Unicode even more. Unicode 3 can represent 256^3 different characters, including languages other than europe and emojis.
These are standard codes for interchanging text and binary code.
| ASCII | Unicode |
| Includes European languages | Includes different languages and emojis |
| Stands for American Standard Code for Information Interchange | Stands for Universal Character Set |
| 1 byte per character | Uses up to 4 bytes per character |
| Requires less space - 8 bit system | Unicode will take up more space as it uses 8-32 bits per character |
| Can only represent letters, numbers, and a selection of special characters, cannot represent characters outside the english language | Allows for a greater range of characters and symbols than ASCII |
15/9/2022
Sound waves are physical vibrations in the air that continuously vary; meaning that they are analogue. Computers cannot process this data, meaning they need to convert it into digital data:
A to D:
To do this, a sample is taken at regular intervals. The amplitude of the wave at a certain time is stored in binary value. The size of the binary value is the sampling resolution. The more bits used to represent the amplitude, the higher quality the data will be. The number of times a sample is taken per second is called the sample rate. The higher the sampling rate, the more accurate the digital representation of the sound wave will be.
D to A:
The computer reads the file and knows the sample rate
The computer reconstructs the sound wave sample by sample
The general shape of the sound wave but may not be as accurate, especially when using a lower sample size
Improving the quality of an audio file by either increasing the sample size by using more bits and increasing the sample rate, increasing the number of times a sample is taken per second. Either of these actions will increase the bit rate and the size of the audio file will increase
Hz = sample rate
Sample rate = number of samples taken in a second
Sample resolution = number of bits used to represent each sample
Channels = A recording can come in multiple channels. It can be either mono (1 channel), stereo (2 channels, or quadraphonic (4 channels).
Calculate file size:
Sample rate * sample resolution * seconds * number of channels
Pros for larger sample rate and resolution:
Higher quality…
Less distortion
Larger dynamic range
Cons
Large file size
Takes longer to transmit files
Takes longer to process
19/9/2022
Bitmap images are made of pixels (stands for picture element)
2D matrix
Every pixel is represented as a binary number
The size of this binary number is the colour depth, which controls the range of colours each pixel can be
Bitmap is a series of binary numbers
Image resolution is the number of pixels within the bitmap
B\&W images only need 1 bit per pixel (0,1). More colours require more bits per pixel. For example, if you need 4 colours then you would need 2 bits per pixel (00, 01, 10, 11).
Formula: x bits = 2^x colours
e.g 3 bits = 2^3 colours = 8 colours
Colour depth is the number of bits used to represent each colour (x from the example)
Most modern computers can represent 24-bit colour depth, almost 16 million different colours.
The more bits per pixel (colour bitmap) the larger the file size. Although the quality is higher, the file will also become larger and slower to load.
Increasing the quality of an image
Colour depth (number of bits per pixel)
Resolution (number of pixels)
Calculating file size:
Colour depth * resolution
ASCII is a type of standard used when interchanging text to binary code for a computer to process. ASCII uses 7-bits, able to represent 128 different characters including european languages, numbers, and some symbols. Extended ASCII uses 8-bits meaning it can represent 256 different characters. It contains many more unique symbols.
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