Computer Science Unit 1

Binary

• Represented with 0b(binary) or (binary)10
• Computer processors are made of transistors, which can be on or off (basically binary)

Hexadecimal

• Noted with 0x or a subscript 16
• Represents 4 bits with 0-F.
• Makes binary easier to read.

Decimal

• Counting system used by humans.
• numbers 0-9.

Left Shift

• 0011010 after left shifting becomes 0110100.
• Left shifting is the same as doubling a number.

Right Shift.

• The same as halving a number..
• 0110100 becomes 0011010.

Binary Addition.

• 1 + 1 = 10
• 1 = 1
• 1 = 0
• 1 + 1 + 1 = 11

Overflow

• When a number gets bigger than the processor expects, the number will be cut off.
• for example: Adding 11111111 to 11111111 will be 100001110.
• But that is1 bit bigger, so that is called overflow.

Ascii

• American Standard Code for Information Interchange.
• It is a way of interpreting numbers as text.
• Original ASCII uses 7 bits to represent the text.
• One more bit was added for extended ascii.

Extended ASCII

• It is a group of different kinds of ASCII, with letters for different languages. To be able to store them, extended ascii uses 8-bits in memory.

Unicode

• Unlike ASCII and Extended ASCII. It uses 16 bits in memory to store one text character. Although this allows for all letters to be used at once, it does use up double the memory per letter than of Extended ASCII. 16 bits is enough to store most special letters of languages, and even start a new form of communication, with emoji.

Bitmap Graphics.

• There are two forms of storing bitmaps.
• The most common one is RGB, which takes in commonly an 8 bit number for Red, Green and Blue. To display a pixel on the image, it can represent more colours, but at a higher memory cost.
• The second one is Index colours which can be thought of as ASCII for colours. It is an 8-bit number representing a colour. The selection is quite limited though. Which is a sacrifice you have to make if you want to cut down on memory usage.

Vector Graphics

• The simplest way to think of these is a mathematical representation of drawings. Vector graphics suffer from one fatal flaw. They only work effectively with clipart-looking drawings. Of course a vector image can still look good, but usually you wouldn't want to store a picture in vector graphics. One major advantage of this format is that because it is a mathematical representation of the image that you see, it doesn't suffer from the limitation that bitmaps suffer from, which is scalability. You can resize vector graphics without losing a bit of quality, which the same cannot be said for bitmap.

Storage of Sound

• Sounds in real life are waveforms. Computers try to recreate that waveform by sampling every so often that waveform. The more samples you take, the more closer you are to the real waveform. This sampling rate is usually measured in Kilohertz. (KHz). The more samples you take the more disk space you take up, but at one point there's no point sampling further since the waveform is really close to it's original.

Metadata

• Extra data about the data stored in a certain file, like creation date, creator, and the software it was created with etc etc. Different files have different metadata.