GSCE computer studdies (edexel) - unit 2 (DATA)

Binary

The binary number system is base 2, using only bits 0 and 1.

Denary

Base 10 number system, how we normally count, uses digits 0 to 9.

Hexidecimal

A base-16 number system that uses sixteen distinct symbols 0-9 and A-F to represent numbers from 0 to 15.

ASCII

a code for representing English characters as numbers, with each letter assigned a number from 0 to 127

Overflow in Binary

Addition is said to overflow if the result is too big to fit in the available digits

Why is hexadecimal used?

- It's easier to read than binary, takes up less space
- Easy to convert from Hex to Binary and vice versa

Bitmap images

Images created using a grid of small squares called pixels

bitmap in binary

The colour of each pixel is represented as a binary number so the whole image is therefore stored as a series of binary numbers.

Pixles

dots that make up an image

Resolution

how many pixels are displayed per inch of an image.

Colour depth

the number of bits used for each pixel in an image file

Amplitude

Each point at every (x,y) is called amplitude or intensity of an image

Sample Rate

the number of samples taken per second, often measured in Kilohertz (kHz)

Sample interval

The time gap between measurements of the sound wave being taken. Another way of expressing the sampling rate.

representation of sound

computer catches sound waves known as analogue sound

equation for file size

File size (bits) = sample rate x resolution x time in seconds

what's data storage measured in

binary multiples

binary multiples

1.bit

Data Compression

A process for reducing the number of bits needed to represent a piece of information

Lossy Compression

data compression techniques in which some amount of data is lost. This technique attempts to eliminate redundant information.

Lossless Compression

a data compression algorithm that allows the original data to be perfectly reconstructed from the compressed data.