1. data representation

Binary system

Binary system

a number system with base 2

Denary system

a number system with base 10

Hexadecimal

a number system with base 16

'A' in hexadecimal system is _____ in denary

10

Overflow

error where the number of bits is not enough to hold the solution

Logical shifts

moving a binary value to the left or to the right, emptied bit is 0

Two's complement

method used to present negative values in binary

MSB is replaced from ______ to ______ in two’s complement

128 to -128

Uses of hexadecimal system

• defining colours in HTML

• MAC addresses

• IP addresses

• assembly languages and machine code

• debugging

• display error codes

• memory dumps

ASCII

7-bit code that represents letters, numbers and characters found in a standard keyboard as well as 32 control codes

Unicode

character code that enables most of the languages of the world to be symbolised with a special character identification

How is sound recorded?

• amplitude of sound wave is determined at set time intervals

• value is converted into digital form

• each sample is encoded as a series of binary digits

• series of readings gives the approximate sound wave

Sampling resolution (bit depth)

number of bits per sample

Increasing sampling resolution...

• increases accuracy of sampled sound as more detailed is stored about the amplitude

• increases memory usage as more bits are being stored

Sampling rate

number of sound samples taken per second in Hz

Increasing sampling rate...

• more accurate sound

• fewer estimations

Bitmap images

made of pixels stored in a computer as a series of binary numbers

Colour depth

number of bits representing each colour

8-bit colour depth

each pixel can be one of 256 colours

Increasing colour depth...

increases size of the file when storing an image

Image resolution

number of pixels that make up an image

Pixelated image

result of low amount of pixels or when zoomed

Increasing image resolution

increases memory usage

8 bits

1 byte

4 bits

1 nibble

Bit

1 binary digit

1 KiB

1024 bytes

1 KB

1000 bytes

Image file size

image resolution (pixels) x colour depth (bits)

Mono sound file size

sample rate (Hz) x sample resolution (bits) x length of sample (s)

Stereo sound file size

sample rate (Hz) x sample resolution (bits) x length of sample (s) x 2

Musical Instrument Digital Interface (MIDI)

• communications protocol that allows electronic musical instruments to interact with each other

• 8-bit serial transmission

• e.g. key on/off, key pressure

MP3

uses audio compression to convert music and sounds

MP4

allows storage of multimedia files like music, videos, photos and animations

JPEG

used to reduce photographic file sizes

Loseless compression

• all data bits from original file can be reconstructed

• used for important files

• repeated patterns are grouped together in indexes

• PNG, ZIP

Run-length encoding

replacing a long series of a repeated character with a count of the repetition

Lossy compression

• eliminates unnecessary bits of data

• impossible to get original file back

• reduces file quality

• MP3, JPEG