Embedded Files
1.2.3 Units
1.2.3 Units
• bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte, petabyte
a bit is a single binary digit (ie can be 0 or 1). A byte is the next main unit it is 8 bits. A nibble is half a byte (ie 4 bits used for conversion from binary to Hex). The following units go up in thousands from the previous unit. A kilobyte is 1,000 bytes. A megabyte is 1,000 kilobytes and so on.
why data needs to be converted into a binary format
why data needs to be converted into a binary format
The circuits in a computer's processor are made up of billions of transistors . A transistor is a tiny switch that is activated by the electronic signals it receives. The digits 1 and 0 used in binary reflect the on and off states of a transistor.
1.2.4 Numbers, Characters, Images Storage
1.2.4 Numbers, Characters, Images Storage
Convert between bases (see how on this link)
• how to convert positive denary whole numbers (0–255) into 8 bit binary numbers and vice versa
• how to convert positive denary whole numbers (0–255) into 2 digit hexadecimal numbers and vice versa
• how to convert from binary to hexadecimal equivalents and vice versa
Adding Binary Numbers (see how)
• how to add two 8 bit binary integers and explain overflow errors which may occur
• binary shifts
1 left shift moves every digit one place to the left drops the first digit and puts a zero in the right most position - effectively multiples by 2 but can be a problem if you have an overflow
1 right shift moves every digit one place to the right, drops the original right most digit. Puts a zero in the 128 position. - Effectively dividing by 2
Characters
Characters
• the use of binary codes to represent characters
ie ASCII, extended ASCII and UniCode
• the term ‘character-set’
collections of characters that a computer recognises from their binary representation
• the relationship between the number of bits per character in a character set and the number of characters which can be represented
ASCII - 7 digits - 128 characters - covers English characters
extended ASCII - 8 digits - 256 characters - Covers English and most European characters)
Unicode - 16 bit (65,536 characters) or 32 bit (4,294,967,296 characters) - covers all languages and things like emojis
Images
Images
• how an image is represented as a series of pixels represented in binary
• metadata included in the file
file format
jpg, png bmp etc
Height
Width
colour depth
ie number of bits used for each pixel (1 bit gives 2 colours, 24 bit gives 16,777,216 colours)
resolution
density of pixels in an image (how many dots per inch) higher the density better the quality
• the effect of colour depth and resolution on the size of an image file.
Increasing the colour depth and/or the resolution will improve the quality of the image and increase the size of the file
Sound
Sound
• how sound can be sampled and stored in digital form
• how sampling intervals and other factors affect the size of a sound file and the quality of its playback:
sampling frequency
how many samples taken in a second
measured in KHz
higher the frequency better the sound
sample size/bit depth
The number of bits used for each sample
higher the sample size better the quality
bit rate
number of bits used per second of audio
bit rate = sampling frequency * sample size
1.2.5 Compression
1.2.5 Compression
• need for compression
make files smaller to save storage space or to transfer over the internet
• types of compression: (lossy, lossless)
lossy - some data is lost when compressed it can't be recovered ideally the viewer/listener shouldn't be able to tell the difference
lossless - compression algorithm is reversed when the file is opened to restore the file to its original state.
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