4) Organisation and structure of data Flashcards
Hexadecimal to binary
Split each character into 4 bits - work out binary for each
Hexadecimal
0 1 2 3 4 5 6 7 8 9 A B C D E F
Denary
Denary/Base 10/ Decimal counting system.
0 1 2 3 4 5 6 7 8 9
Binary
Base 2/ Binary digits 1 0 Bits 1 = on 0 = off
Arithmetic shift
Shifts are manipulations of bit patterns.
Moving the bits a specified amount of times each direction.
How sound can be stored digitally
Sound is converted into a digital signal by sampling
Sampling is when a device measures the level of
sound many times per second and records this as binary digits
How an image is represented by pixels in binary format
1 = black pixel 0 = white pixel
Colour bitmap is stored by replacing 1s and 0s with a longer number that represents RGB
Why metadata needs to be included
metadata = data about data
Needed to store an image correctly
Image’s height, width, colour depth
Binary digits representing chartacters
Unicode
Ascii
(American standard code for information interchange)
Data types
Integer Real Boolean Character String
Data structure
Specific way of organising data within memory so that it can be processed efficiently.
Static data structure
Designed to store a know number of data items.
Values can be changed but memory size is fixed
Dynamic data structure
Designed to allow the data structure to grow and shrink at runtime
List
Data items stored in the order they were originally added to memory
Array
Data structure that can hold a fixed number of data items which must be same data type.
1D array
Used to store a list of data in memory that can be used by a program at runtime.
Insertion
You can add an element to an array at a given index
myArray[3] = 27
Traversing
Using a loop to use each element of an array in a section of a program
Deletion
myArray[6] = “”
Search
Arrays can search using the index or the value stored
2D array
Must all be same data type
Table with columns and rows
Records
Records can hold all data types
Uses more memory - less efficient
Key field
An item of data that is unique and can be used to identify the individual record
Validation
Process to check if data is reasonable or sensible
DOES NOT CHECK IF DATA IS CORRECT