What is the denary counting system also known as?
The denary counting system is also known as the Base 10 or decimal counting system
How does the denary counting system represent data?
The digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 are used to represent numbers, e.g. 138 1 ‘hundred’ 3 ‘tens’ 8 ‘units’
What is the binary counting system also known as?
Binary counting systems is also known as the Base 2 counting system
Why must data be converted to binary format in order for it to be processed by a computer system?
Computer systems can only store and process binary digits, BITs, which are either a 1 or a 0
A binary number is ___ bits
A string of
What is the hexidecimal counting system also known as?
The hexadecimal counting system is also known as the Base 16 counting system.
How are numbers represented in the hexadecimal system?
In the hexadecimal counting system,
the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 are used to represent 1–9 and then the characters A, B, C,
D, E and F are used torepresent 10 –15.
Why are hexadecimal numbers widely used rather than binary?
Hexadecimal is widely used as binary numbers can be quickly converted into hexadecimal numbers that are more convenient for humans to use.
What are shifts and what do they involve?
Shifts are manipulations of bit patterns. A shift involves moving the bits in a specified direction, either left or right, by a specified number of places
What can arithmetic shifts be used for?
Doing division and multiplication
What does logical shift right do?
Logical shift right divides a number by 2 with every shift
How does logical shift right work?
- What was in bit position 0 (the right most bit) falls off the end and is lost forever.
- What was in bit position 1 moves to bit position 0.
- What was in bit position 2 moves to bit position 1.
- A 0 is moved into bit position 7.
What is the sign bit?
One way to represent negative numbers is through sign and magnitude. In this method, the bit at the far left of the bit pattern - the sign bit - indicates whether the number is positive or negative. The rest of the bits in the pattern store the size of the number (called its magnitude).
For example, with an 8-bit pattern, the first bit would be used to indicate positive or negative.0 can indicate a positive number and a 1 can indicate a negative number. The other seven bits would be used to store the actual size of the number.
For example, 10001001 could represent -9:
What does arithmetic shift left do?
Arithmetic shift left multiplies an integer (binary number) by two
What happens when the sign bit is eventually changed in arithmetic shift left?
An overflow occurs
How does arithmetic shift left work?
- What was in bit position 0 moves to bit position 1.
- What was in bit position 1 moves to bit position 2.
- What was in bit position 7 (the left most bit) falls off the end and is lost forever.
- A 0 is moved into bit position 0.
What does arithmetic shift right do?
Arithmetic shift right will divide a binary number by 2 with every shift and preserve the sign of the number
How does arithmetic shift right work?
The normal shift takes place, but the sign bit stays the same as the data shifts. So if the sign bit was 0, it will be filled in with a 0, if it was 1 it will be filled in with a 1
How long can arithmetic shift left last for?
Arithmetic shift left works until the sign bit is changed, then an overflow occurs
What is the process that converts sound into a digital signal called?
What happens in sampling?
Hardware measures the level of sound many times per second and records it as binary digits
What is the sampling frequency?
The sampling frequency is the number of times that sound level is sampled per second
The higher the ___ the ___ the quality of sound
Sampling frequency, higher
What is bit rate (sound)?
The number of bits used per second of audio
What is bit depth (sound)?
Bit depth is the number of bits available for each clip of sound
How are bitmap images stored?
Botmap images are stored as an array of pixels
How will a black and white bitmap image be stored?
It will be stored as an array with a 1 representing black pixel and 0 a white pixel
How is a colour bitmap image stored?
It is stored in an array where each pixel is represented by a number that represents how much red, green and blue is required in the colour of it
What is colour depth (of an image)?
It is how many colours are available for each pixel and is measured in bits
What values would a 1 bot colour depth, 2 bit colour depth allow for?
1 - 1 or 0
2 - 00 01 10 11
How do you calculate the number of colours available for each pixel (colour depth)
So 5 bit colour depth 2^5 allows for 32 colours
How many bits colour depth is needed for RGB?
24 bits will be needed, each pixel stores 24 bits, the first 8 e.g. 11111111 give red value, next 8 green etc. Each can store a number from 0-255
What is the general file format for vector images?
SVG - scalable vector graphics
What are some common bitmap file types?
JPEG, GIF, PNG
What is done when zooming in on bitmap images?
When zooming in on bitmap images the pixels are stretched and enlarged
How is a vector image stored?
A vector image uses scalable shapes e.g. lines and curves, using coordinates and geometry to precisely define parts of the image
Why are vectors more efficient than bitmaps at storing large areas of colour?
Vectors do not need to store every pixel as bitmaps do so they are more efficient at storing large areas of one colour
How are vector images displayed?
When a monitor wants to display a vector image it is rasterised - converted into a grid of pixels to be displayed
What does metadata mean?
Metadata means ‘data about data’
What would metadata contain (4 examples)?
- colour depth
- file format
- time and date when image changed
- camera settings when image taken
Why is metadata necessary?
Metadata allows a computer to display an image correctly
How are characters stored on a computer system?
Characters are stored as a binary number on a computer system
What is a character set?
A character set is a table that maps a character with a unique binary number
Why is a character set needed?
A character set allows for data exchange between computer systems as it allows them to recognise which binary number corresponds to which character as computer systems can represent characters differently
What does ASCII stand for and what is it?
ASCII stands for American Standard Code for Information Interchange and is a 7- it character set
What is the problem with the ASCII character set?
The problem with the ASCII character set is that it can only represent 128 different characters, and computer systems may need to be able to store more characters than this
What is unicode and why is it useful?
Unicode is a standard character set that has combined and replaced many others. It allows for many different characters to be represented, many more than ASCII
What does a real store?
Numbers, including fractions or decimals
What are the most common data types?
Integer, real, boolean, character, string
What is a data structure?
A data structure is a specific way of organising data within memory so that it can be processed efficiently
What is a static data structure used for?
A static data structure is used to store a known number of data items
What can be changed and what is fixed in a static data structure?
The values of data in a static data structure can be changed but the memory size is fixed.
Why is an array an example of a static data structure?
You can change the values of elements in an array, but the size of it is (memory size allocated) is fixed
When is memory allocated to data structures?
Memory is allocated to data structures at compile time
What is the advantage of static data structures?
Static data structures are easier to program as there is no need to check the size of the data structure or number of items stored
What is different about dynamic data structures from static data structures?
Dynamic data structures are designed to allow the data structure to grow or shrink at runtime, it is possible to add or remove elements without having to consider memory space
What is the advantage and disadvantage of dynamic data structures?
Dynamic data structures make the most efficient use of memory but are more difficult to program
How does a list data structure store data?
A lost stores data items in the order they were originally added to memory
Is a list data structure dynamic or static?
If the list is made up of a set of number data items it can be static as the size is known, but if it varies in the number of data items it would be a dynamic data structure
What is an array?
An array is a data structure that can hold a fixed number of data items of the same data type.
How are elements in an array identified?
The elements in an array are identified by a number indicating their position in the array known as the index
What are the basic operations that can be carried out in a one-dimensional array?
Transversing, insertion, deletion, search
What is transversing (arrays)?
Transversing an array means using a loop to use each element in a section of a program (e.g. looping through a list, printing out each item)
What is insertion in an array?
Insertion is adding an element into an array at a given index
What is the index (arrays)?
The index is a number that indicates the position of an element in an array
What is deletion in an array?
Deletion is removing an element from an array
What is search in an array?
Areays can be searched using the index or the value stored at the index
How are elements in a two dimensional array indexed vs a 1 dimensional array?
In a two dimensional array elements are indexed by two numbers, one for the row and one for the column unlike in a one dimensional one only one index number
What are records used for?
The record data structure is used to store related data of different data types
How are records made up?
A record is made up of information about a person or thing, called a field. This is split up into a field name and field type
What is a key field?
A key field is an item of data that is unique and can be used to identify the individual record. Each record in a file should have a key field
How is a stored file output to the screen?
A program will load a file from secondary storage, e.g. hard disk, into the computer’s memory. The data will be manipulated bu the CPU and output to the screen.
What is a file format?
A file format is a structure and organisation that data stored in a file would have
How would it be most efficient to store the fields in a record in a data file and why?
It would be most efficient to store the fields in the record next to each other so that the data can be put into the record data structure in memory to be processed by the CPU
What makes up files?
Files are made up of records of the same structure
What makes up records?
Records are made up of fields containing information about a person or item
What is validation?
Validation is a process used to check if input data is reasonable or sensible
What are presence checks validation algorithms used for?
They are used to prevent further progress if a field is left blank
What are Format checks validation algorithms used for?
Format checks are used to ensure data matches a specific pattern, e.g. did/mm/yyyy
What are Length checks validation algorithms used for?
Length checks are used to ensure that an input data string is a sensible length
What are Type checks validation algorithms used for?
Type checks are used to ensure that input data are a particular data type
What are Range checks validation algorithms used for?
Range checks are used to ensure that input data lies within a specified range
What are Look up checks validation algorithms used for?
Look up checks are used to ensure input data matches an item in a list of valid entries
What is verification?
Verification is a process for chewing if data is correct
When could verification be carried out?
When a user enters data, or when data is copied from one part of the system to another
How does double entry data verification work?
Double entry involves using a verification algorithm to compare two versions of data input and inform the user if they are identical
How does screen based verification work?
Screen based verification requires the user to check a display of input data and confirm that it is correct