Note containing summarized school notes, main textbook and revision guide textbook. Hence no need to buy textbooks since all the information is in this note. Have achieved full UMS marks (with A*). Note owner has received 11A* and 1A in her GCSEs.
CHAPTER 1 – DIGITAL DATA (UNIT 1: Digital Technology)
THE NAME OF THIS GCSE: DIGITAL TECHNOLOGY (MULTI-MEDIA)
HOW LONG IS THE TEST FOR UNIT 1: 1 HOUR
HOW MUCH IS THE PERCENTAGE WORTH FOR UNIT 1 OF THE OVERALL GCSE: 30%
Data Types
Computers store data in the form of billions of combinations of switches (0 = off, 1 = on).
There must be a way of telling computer systems what type of data they are currently working
with so that they can process data of Numeric Integers/Real Numbers, Date/Time, Character &
String.
Data is stored in appropriate way to optimize a computer’s processing power.
Thus, data must be defined as a certain type before it is processed.
Representing data
Data: UNPROCESSED RAW FACTS AND FIGURES WITH NO MEANING ATTACHED TO IT
(ex: the numbers 1, 2, 3, 4 without meaning)
Information system: PROCESSED DATA WHICH HAS BEEN PLACED IN CONTEXT AND GIVEN A MEANING
(ex: list of pupils in a class and their test scores)
Consists of hardware and software working together {takes data as input and converts it into
information}.
INFORMATION SYSTEM PROCESSES DATA AND PRODUCES INFORMATION
Input Data Information System Will Process The Data Output Information
Data processed (given meaning) Information given
Ex: [62351 = table in the margin data] Add meaning to this sequence of figures [product number
62351 is a 2Tb portable hard drive] Information
,Representing Data Using ASCII
1. Make sure the number lock is on.
2. Click and hold the Alt key.
3. Use the number pad on the right hand
side to type in the code.
4. It will change it into a letter after.
Storing Data
Computers store data in digital format, done by number system, BINARY.
Binary digit:
Known as bit
Has a value of 0 or 1
Smallest unit of computer storage
Byte:
Bits grouped in groups of eight = BYTE
Single character (letter/digit) = represented by 1 byte (8 bits)
A nibble = represented by 4 bits
[two nibbles = 1 byte]
Storing capacity of a computer’s memory:
Measure in bytes
[binary digit (0 or 1) = 1 bit]
[4 bits or half of byte = 1 nibble]
[8 bits = 1 byte (B)]
[1024 bytes = 1 kilobyte (kB)]
[1024 kilobytes = 1 megabyte (MB)]
[1024 megabytes = 1 gigabyte (GB)]
[1024 gigabytes = 1 terabyte (TB)]
These terms describe data storage capacity (of USB flash drives) and computer memory.
Characters are classified as letters, digits, punctuation marks.
[a commonly used character set = ASCII (American Standard Code for Information Interchange)]
,Representing Images
Pixel:
Represented by a dot or square.
Smallest unit of a digital image that can be displayed on screen.
Can be edited on a computer screen.
Each pixel – has own individual colour.
Pixels combined together = Complete image.
Number of pixels on computer screens depends on the size of screen and the graphics card used by
the processor.
Pixels stored as a series of binary digits.
Number of bits used to store a pixel depends on the range of colours used.
Image Resolution:
Tells the quality of an image [the amount of pixels vertical and horizontal].
Greater pixels used = Higher the resolution & Sharper the image
= More storage space used/needed
Represented by 2 numbers (Ex: 1280 * 720):
o FIRST NUMBER = number of pixels displayed horizontally
o SECOND NUMBER = number of pixels displayed vertically
POSITION OF A PIXELS IN AN IMAGE IS GIVEN USING A SYSTEM SIMILAR TO (X,Y) COORDINATES.
QUESTION: HOW DOES THE NUMBER OF PIXELS AFFECT THE RESOLUTION OF THE IMAGE?
The resolution of the image depends on the number of pixels available to represent the image as
accurately as possible. Therefore, the smaller number of pixels limits out the variety of the pixels used in
order to represent the image. The greater the number of pixels, more of the image can be shown precisely.
Bitmap Graphics
Made up of a grid of pixels which have many different colours and are possible to edit each
individual of each pixel.
Information about each individual pixel that makes up the image is stored in the image file.
Can edit each individual pixel resolution.
Using mobile phone to take photograph, Using computer to scan a picture
= Creating a bitmap image
Higher resolution of the device (ex: mobile-phone camera) = More pixels = Higher quality of image
= More storage space to save the image
Store details about every individual element (pixel) of the image:
o Different colours used in each pixel
= File size of a bitmap image can be very large as the computer has to store every pixel
= Large bitmap images can take a long time to load from the computer’s memory
o This can be complex.
Can be compressed to reduce the file size = Loss of quality
Zooming in or enlarging a bitmap image = PIXELATION (pixels become larger on screen and look like
number off blocks put together) Bitmap images are poor quality when enlarged too much
QUESTION: SARAH’S DAD IS A PROFESSIONAL PHOTOGRAPHER. HE SOMETIMES HAS TO EDIT THE IMAGES
HE HAS TAKEN. GIVE TWO REASONS WHY HE SHOULD SAVE HIS PHOTOGRAPHS IN BITMAP
FORMAT.
1. Can edit each individual pixel.
2. Can adjust the resolution of the picture being taken. (Higher resolution = Higher quality)
QUESTION: LIST TWO DIFFERENCES BETWEEN BITMAP AND VECTOR- BASED GRAPHS.
1. Bitmap Graphics rely on resolution for quality (not on mathematical formula and shapes).
2. Bitmap Graphics are made up of grid of pixels.
,Vector-Based Graphics
Uses of mathematical objects (lines, curves, shapes/polygons) to represent images in computer
graphics.
Not made up of a grid of pixels = Even when enlarged, do not lose image quality
Store information about the components that make up an image
[COMPONENTS based on MATHEMATICAL OBJECTS: lines, curves, shapes
Possible to edit these objects separately: changing colour, size, position of the object]
Do not depend on resolution for quality.
Store details about the shape of individual image objects
– require less storage capacity compared to the use of pixels (less information need to be stored)
= Saves as smaller files & Easily can be edited without loss of quality
QUESTION: LIST TWO DIFFERENCES BETWEEN BITMAP AND VECTOR- BASED GRAPHS.
1. Vector graphics rely on mathematical formula and shapes (do not rely on resolution for
quality).
2. Vector-based graphics are not made up of a grid of pixels.
Buffering & Streaming A Video
Video files store a very large amount of data.
Streaming (Service):
A process that allows a large video to be viewed on a website or app straight away without having
to wait for the full video to be downloaded entirely first or without even downloading.
[User can start watching video as it downloads in ‘real time’ rather than downloading and
permanently storing to complete video to be watched later.]
Buffer:
An allocated part of memory that is used to store a downloaded part of the video before it is
watched.
[While the user is watching a video (when the current snippet of the video is being watched), a
buffer is used to download the next part (it holds the next bit then releases it for viewing and
repeats this process).]
Used to help make the playback smooth.
This process helps to prevent possible disruptions in streaming while the video is playing.
{If speed of the internet connection is inconsistent or the internet connection is temporarily lost
Buffering helps to improve the streaming experience}
QUESTION: HOW DOES BUFFER ASSISTS THE PROCESS OF VIDEO STREAMING?
The video cannot play straight away without anything stored in the computer. Therefore, as soon as the
video is played, the buffer stores the first part of the video, allowing the user to watch the video straight
away. This continues until the end of the video, meaning that there would be the fully downloaded video.
, Representing Sound
QUESTION: JUST AS WITH REPRESENTING TEXT AND IMAGES, WHY DOES THE SOUND ON A COMPUTER
SYSTEM MUST BE REPRESENTED AND STORED DIGITALLY?
Because computers store data with just billions of switches and everything needs to be
broken down into various combinations of on/off (binary) so that the computer can do
something with them.
When a sound file is converted from an analogue signal to a digital signal after being recorded using a
computer, the 3 factors that affect the quality of digital audio/sound are:
o SAMPLE RATE –
o Number of audio sound samples captured in sound wave every second to represent the
sounds digitally.
o Measured in Hertz (Hz).
o More samples taken per second = More accurate the digital representation of the original
sound [Higher quality of sound] & The shape of the sound wave is captured more accurately
o BIT DEPTH –
o Number of bits used to store each sound sample.
o Measured in bits per second.
o Known as Sample Format or Resolution
[Sample Format = terminology used in Audacity’s Quality Preferences]
o Higher quality sound requires = Higher bit depth
o Bit depth is usually 16 bits on a CD [CD: has a resolution of 65536 possible values (2 16)].
o Bit depth is higher on a DVD which is usually 24 bits.
o BIT RATE –
o The quantity of overall data measured in bits that is processed in a given amount of time.
o In Kilobits (KB) per second
Number of bits stored overall = Number of total second in a sound file
{a typical iTunes song stores 256 Kilobits of data in every second of a song}
AMPLITUDE = VOLUME OF SOUND
(the height of the wave above or below the line)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller KimmyTikky. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
