Unit 2.1.1. Revision April 2023.pdf

GCSE Digital Technology UNIT 1: THE DIGITAL WORLD Section 2.1.1. - Data Name: Target grade: Teacher: Option: 1 PAGE 1. TYPES OF DATA 2. MEASURING AND STORING DIGITAL DATA Analogue and Digital Data 3-4 Analogue and Digital Devices 5 Binary Digits 7-10 Magnetic Storage 11-12 Optical St...

GCSE Digital Technology UNIT 1: THE DIGITAL WORLD Section 2.1.1. - Data Name: Target grade: Teacher: Option: 1 PAGE 1. TYPES OF DATA 2. MEASURING AND STORING DIGITAL DATA Analogue and Digital Data 3-4 Analogue and Digital Devices 5 Binary Digits 7-10 Magnetic Storage 11-12 Optical Storage 13 Solid-State Storage 14 Cloud Storage 15-16 Digital Sound 3. DIGITAL CONVERSION AND PROCESSING Analogue to Digital Conversion 19 Digital to Analogue Conversion 20 Recording and Sampling Digital Sound 21-22 Storing Digital Sound Compression techniques 23 Digital Images Bitmap Images 26-28 Vector Images 29 Storing Digital Images Compression techniques 30 2 1. Types of Data Analogue and Digital Data Analogue Data is used by humans to process information. Humans need analogue data to make sense of the world around us, for example to see and hear things. Everything you see or hear is an uninterrupted flow of data to your senses. Analogue Data: is a continuous range of values   changes smoothly Analogue Data cannot be processed by a computer, It needs to be converted to digital data before a computer can use it. Digital Data is used by computers to process information. Devices such as mobile phones and tablets store photos, music, video and text digitally. Digital Data:   is stored as discrete values is made up of Binary Digits (bits) Digital Data cannot be processed by a human. It needs to be converted to analogue data before a human can use it 3 Analogue and Digital Data - Examples Clocks On this analogue clock the second hand moves continuously and smoothly. This digital clock can only show discrete changes in time, at one-second intervals For example: For example: Between 3:07 and 3:08 this clock can display all values of time. Between 3:07 and 3:08 this clock can only display 60 discrete values: 3:0700 3:0701..........................................................3:0758 3:0759 Thermometers This analogue thermometer (the alcohol or mercury thermometer used in science lessons) displays temperature continuously and smoothly This digital thermometer can only display discrete changes in temperature at 0.1⁰c intervals For example: For example: Between 37⁰c and 38⁰c this thermometer can display all values of temperature Between 37⁰c and 38⁰c this thermometer can only display 10 discrete values: 37.0⁰c 37.1⁰c ............................................ 37.8⁰c 37.9⁰c 4 Analogue and Digital Devices Examples of other analogue devices Weighing Scales Cassette Tape Guitar Film Camera Examples of other digital devices Digital Camera Tablet Smart Phone VR Headset 5 Analogue and Digital Devices - Revision Activities 1. Name two analogue devices (3) ................................................................... ................................................................... ................................................................... 2. Name three digital devices (3) ................................................................... ................................................................... ................................................................... 3. Describe the difference between analogue and digital data (2) ............................................................................................................................................................................................................................ ............................................................................................................................................................................................................................ ............................................................................................................................................................................................................................ ............................................................................................................................................................................................................................ 4. Match up the following facts depending on whether they apply to analogue or digital devices. An example has been done for you (8) Is processed by humans Is made up of binary digits Is stored as discrete values Is a continuously range of values ANALOGUE Changes smoothly Cannot be processed by humans DIGITAL Is processed by computers Is used by devices such as mobile phones Cannot be processed by a computer 5. What needs to happen to analogue data before it can be processed by a computer (1) ............................................................................................................................................................................................................................ ........................................................................................................................................................................................................................... 6 2. Measuring and Storing Digital Data Digital devices cannot process analogue information, they can only process digital data. Digital data is made up of binary digits. Binary is a number system that only uses two digits: 1 and 0. These are known as bits. Bits are the smallest pieces of data that a computer can process/store. All information that is processed by a computer is in the form of a sequence of 1s and 0s. Therefore, all data that we want a computer to process needs to be converted into binary. 1 binary digit is called A bit 4bits are called a A nibble 8 bits are called A byte 7 When you press a key on a keyboard, an electrical signal is sent through the wire into the computer. One key press sends 1 byte (8 bits) of data n The computer converts this byte of data and displays the key you pressed on the screen. 01101110 Every key on a keyboard has its own binary value. This is known as ASCII code. 01110000 01101111 01110001 Part of the ASCII code table is shown here. 01110010 * * 00100000 Scan the QR code below or follow the link to find out more about the bits, bytes and binary storage tinyurl.com/bitsbytes2020 8 Measuring and Storing Digital Data - Revision Activities (1) 1. Fill in the gaps below (3) A bit is either a ……………..…. or a ……………..…. When 8 bits are stored as a binary number, they are called a ………………….. 2. Complete the table below (6) Measure Name 4 bits …………………………….. …………………………….. bytes 1 kilobyte ……………………………..GB 1TB …………………………….. kilobytes 1MB 1,048,576MB …………………………….. 1,048,576 bytes …………………………….. 3. How many bits are there in a byte (1) ................................................................... 4. How many bits in a nibble (1) ................................................................... 5. Name the coding system used to convert letters pressed on a keyboard into binary (1) ................................................................... 6. Describe two features of digital data (2) ....................................................................................................................................................................................................................... ....................................................................................................................................................................................................................... ....................................................................................................................................................................................................................... 7. Describe two features of analogue data (2) ....................................................................................................................................................................................................................... ....................................................................................................................................................................................................................... ....................................................................................................................................................................................................................... 9 Storage Mediums Digital data is stored using different storage devices known as mediums. Users will choose from different types of storage for different activities. Magnetic Storage Mediums Magnetic storage uses a magnetisable coating. Magnetised dots are made on the surface of the material. These dots are created, read and deleted by very small electric magnets. Examples include:  Computer hard-drives  Digital cassette-tapes Common uses:  Saving work on a computer  Backing up work on a network Amount of storage:  An average desktop PC has a 1TB capacity hard-disk.  Most digital cassette-tapes have a maximum storage of 1TB ADVANTAGES OF MAGNETIC STORAGE DISADVANTAGES OF MAGNETIC STORAGE Large capacity, they can store several terabytes of information Not as portable as other technologies. External hard disks are commonly available, but they need to be treated carefully. Low cost per gigabyte - magnetic tape is the Hard-disks have mechanical moving parts, so are cheapest, but hard disk is very low cost as well. less rugged than other storage types Hard Disk offers high speed data retrieval Data can be lost near strong magnetic fields, such as being too near a music speaker Hard Disk offers random access to data. Magnetic tape is very slow. Magnetic tape can hold its data for up to thirty years in the correct environment. Data isn’t accessed as fast as on solid-state devices 11 Storage Mediums Magnetic Storage Mediums —Computer Hard Drives The hard disk is the main storage device in a computer. It works like a filing cabinet: all of your data files and applications software are stored on it. The hard disk contains a number of metal platters which have been coated with a special magnetic material. The data is stored in this magnetic material. In order to access the data, the platters spin many thousands of times a second and a magnetic read and write head floats just above the surface of the platter. When you hear the term 'hard disk crash', this refers to the read/write head crashing down onto the surface of the hard disk. There is a risk every time this happens that the data stored in the section just where the head crashes might be damaged. That is why it is a bad idea just to switch the computer off at the wall without shutting it down properly. There may even be several hard disks fitted inside some computers . Scan the QR code below or follow the link to find out more about how hard-drives work. Watch the video until 13:40 tinyurl.com/harddrive2020 12 Storage Mediums Optical Storage Optical storage uses a laser to shine and reflect light to read stored data. Examples include:  DVD  Blu-ray  CD Common uses:  Storing music and movies  Copying and sharing music files Amount of storage:  A single-sided DVD can store 4.7GB of data. A double-sided DVD can store 8.5GB of data.  A single-sided Blu-ray disc can store 25GB of data. A double-sided Blu-ray disc can store 50GB  A CD can store around 700MB of data ADVANTAGES OF OPTICAL STORAGE DISADVANTAGES OF OPTICAL STORAGE Cheap if less than 10GB needs to be stored per media item. Not cheap if terabytes need to be stored Very portable compared to hard disk Not as portable as Flash media (like USB) Ideally sized for storing movies and videos. Slow to write (burn) to and much slower data retrieval than a hard disk. They are not affected by magnetic fields. Easily scratched Scan the QR code on the right or follow the link to find out more about blu-ray and other optical storage tinyurl.com/bluray2020 13 Storage Mediums Solid-state Storage Solid-state storage has no moving parts. It holds data using electronic switches. If the switch is open, it represents a '1', since it retains an electric charge. If it is closed, it represents a '0'. It is an electrical form of storage, unlike magnetic or optical media. It is also known as 'Flash memory'. Examples include:  USB  SSD drive  SD cards Common uses:  USBs are used to store and transport computer files  SSD drives are used for storage in computers (instead of magnetic hard-disks)  SD cards are used to store and transfer photos when using a digital camera Amount of storage:  The maximum storage of a USB is 1TB of data. Common USB will store 256TB to 512TB  An SSD drive can store up to 100TB of data  An SD card can store up to 2TB of data ADVANTAGES OF SOLID-STATE STORAGE DISADVANTAGES OF SOLID-STATE STORAGE Faster data retrieval than hard disk as there are no mechanical parts need to be moved to read / write data.. Solid State Drives are expensive compared to a hard disk of similar capacity. Large capacity, especially SSD drives SSDs don’t last as long as hard-disk drives Very tough and rugged as it has no moving parts unlike a hard disk USBs are easily lost or stolen. This has lead to data security concerns. Some companies use encrypted USB sticks Very portable in the form of SD memory cards and USB memory sticks The cost of recovering information from an SSD is higher than from hard-disk drives 14 Storage Mediums Cloud Storage Cloud storage stores data at a remote location online. When files and data are sent to the cloud, they are actually being sent to a server that is connected to the internet. Files can be uploaded to a folder system and downloaded as required. The cloud is also used for internet-based software and apps like Google Classroom and Microsoft Office online. Examples include:  Google Drive  Microsoft OneDrive  Apple iCloud Common uses:  Storing school work files  Backing up a computer hard-drive  Backing up music and photos from a phone Amount of storage:  Most cloud storage will offer around 5-20GB of free storage  You can have as much cloud storage as you like - but the more you store, the more you pay  The amount of data in stored in the cloud is increasingly daily. In 2020 it was estimated that there was over 100,073,741,824GB in cloud storage 15 Storage Mediums Cloud Storage ADVANTAGES OF CLOUD STORAGE DISADVANTAGES OF CLOUD STORAGE Data is safely backed up at a remote location so even if you have a disaster such as a fire there will always be a secure backup of your files The network connection has to be very reliable if the connection is slow or unreliable you might not be able to access your files. Speed of data retrieval will depend on the network connection. You can access your files from anywhere with a network connection, you aren't tied to your machine at home There are concerns about data security. You need to be certain that the company is reputable i.e. that they will perform regular backups of your data and that they have good security in place so that no one can access your data. It usually costs money to store data in the cloud. A company does not have to pay the energy costs Some businesses might give you a small amount of of running a large server. storage space for free but will charge for providing extra space. Data storage is more efficient because you only pay for the exact amount of data you need to store. Scan the QR code below or follow the link to find out more about the durability of some different storage mediums. tinyurl.com/cloudstorage2020 If the data storage company goes out of business then all of the data stored on their servers may be lost (or not available to access) Scan the QR code below or follow the link to find out more about the durability of some different storage mediums. tinyurl.com/compared2020 16 3. Digital Conversion and Processing Digital Sound When musicians create sounds using their voice or a musical instrument they produce analogue data. We have already learned that humans process analogue data and computers process digital data. If a musician wants to record and edit their music on a computer then they will have to convert the data from analogue to digital. ANALOGUE TO DIGITAL CONVERSION Will is a professional musician he wants to record a new song he has written. Then he wants add some effects using his computer. Will sings into a microphone that is connected to his computer. The sound waves that Will produces as he sings are analogue data. Will’s voice is converted into digital data by a device inside the computer called an analogue to digital converter (ADC). The ADC is usually located on a computer’s sound card. Will’s computer can now process his voice recording. He can use apps to add effects like echo or extra bass. 19 Digital Sound When musicians have edit sound on a computer they produce digital data. We have already learned that humans process analogue data and computers process digital data. If a musician wants to be able to listen to their edited music then they will have to convert the data from digital to analogue DIGITAL TO ANALOGUE CONVERSION Will has added an echo effect to his voice using an app on his computer. He now wants to listen back to his song. Will’s voice is converted into analogue data by a device inside the computer called an digital to analogue convertor (DAC) The DAC is usually located on a computer’s sound card. Will can now listen to his voice using the headphones he has connected to his computer. ANALOGUE TO DIGITAL CONVERSION DIGITAL TO ANALOGUE CONVERSION 20 Recording and Sampling Digital Sound Analogue sound can be represented as a sound wave. This sound wave lasts for 10 seconds When a music is recorded onto a computer a process called sampling takes place. In this example, the computer takes one sample per second. Most audio is recorded at over 40,000 samples per second Any sound that takes place between samples is not recorded. This means that the sound loses quality as data has been lost between the time samples. The way to increase the quality and store the sound at a quality closer to the original, is to have more time samples that are closer together. The higher the sampling rate and the bit depth, the better the quality of the recording. 21 Digital Sound SAMPLING RATE BIT DEPTH The amount of samples taken per second is called the sample rate. Bit depth is the number of bits available for each sample. The higher the bit depth, the higher the quality of the sound. The sample rate is measured in Hertz (Hz). SPOTIFY CD Sampling Rate: 48,000Hz Sampling Rate: 44,000Hz Bit Depth: 24 bit Bit Depth: 16bit It is possible to change the sample rate and bit depth that your computer plays through your speakers or headphones. Scan the QR code below or follow the link to find out more about sound recording and sound quality tinyurl.com/soundquality2020 Scan the QR code below or follow the link to find out more about sound sampling tinyurl.com/sampling2020 Scan the QR code below to see how well you can tell the difference in quality of different sound files tinyurl.com/soundquiz2020 22 Storing Digital Sound Digital sound can be stored in many different file types. Choosing between different sound file formats has an effect on the overall sound quality and file size. Uncompressed Digital Sound Uncompressed sound files are high-quality recordings. Uncompressed files normally have a higher sampling rate and bit depth. They are also known as lossless audio. Uncompressed sound files are usually used by professional musicians and in recording studios. Examples of uncompressed sound files: WAV FLAC Average file size of a 3 minute song: 1800MB Average file size of a 3 minute song: 900MB The main advantage of uncompressed digital sound is that they sound almost identical to the original analogue sound recording. A major disadvantage is that the file size of a WAV or FLAC song will be a lot bigger than one that has been saved in a compressed format. Compressed Digital Sound Compressed sound files are lower-quality recordings. Compressed files normally have a lower sampling rate and bit depth. They are also known as lossy audio. Compressed sound files are usually used as music downloads or files from online streaming sites. Examples of compressed sound files: MP3 WMA Average file size of a 3 minute song: 30MB Average file size of a 3 minute song: 30MB The main advantage of compressed digital sound is that because the file size is smaller, a user can download many files onto their device. A disadvantage is that the sound quality is not as good. Many users cannot tell the difference between a compressed and uncompressed sound file. 23 Digital Sound - Revision Activities (1) 1. Name the device that changes a human voice into digital data so it can be processed by a computer (1) …………………………………………………………………………………………………………………………………………………………………… 2. Name the device that changes digital data into sound that can be heard by a human (1) …………………………………………………………………………………………………………………………………………………………………… 3. If sampling takes place at 100Hz, how many samples are being taken per second? (1) …………………………………………………………………………………………………………………………………………………………………… 3. Explain how the sample rate and bit-depth affect the quality of a recording (2) …………………………………………………………………………………………………………………………………………………………………... …………………………………………………………………………………………………………………………………………………………………... …………………………………………………………………………………………………………………………………………………………………… 4. Sample A and Sample B show the same piece of music that has sampled twice at different sample rates. Identify which sample has the higher sample rate. (1) Sample A Sample B ……………………………………………… 5. Users can choose between compressed and uncompressed audio. Explain the difference between these two types of audio. Give one advantage and one disadvantage for each. (6) …………………………………………………………………………………………………………………………………………………………………... …………………………………………………………………………………………………………………………………………………………………... …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………... …………………………………………………………………………………………………………………………………………………………………... …………………………………………………………………………………………………………………………………………………………………… 24 3. Digital Conversion and Processing Digital Images BITMAP IMAGES To store an image on a computer, the image is broken down into tiny elements called pixels. A pixel (short for picture element) represents one colour. A pixel is the smallest unit of a digital image that can be displayed and edited on a computer screen. Each pixel can have its own individual colour and when pixels are combined together they produce a complete image. Images made up of pixels are known as bitmap images. They are sometimes called raster images. Binary Codes for this image In this black and white picture, each pixel is represented by one bit. 000000 010010 010010 000000 011110 For coloured pictures , each pixel is represented by at least two bits. The number of bits used for each pixel is known as the colour depth Binary Codes for this image 101010101010 100010100010 101110101110 101010101010 100101010110 Resolution Image resolution tells us the quality of an image. The greater the number of pixels used in an image, the higher the resolution and the sharper the image. However, higher resolution images need more storage space. Image resolution is represented by two numbers, such as 1280 × 720. The first number is the number of pixels displayed horizontally and the second number is the number of pixels displayed vertically. The position of a pixel in an image is given using a system similar to (X, Y) coordinates. 26 Digital Images Scan the QR code on the right or follow the link to find out more about storing Bitmap images tinyurl.com/bitmap2020 1. 2. Create your own black and white bitmap image using the grid below. Convert your bitmap image into binary. Use ‘1’ for a black pixel and ‘0’ for a white pixel For example: 01011001 3. How many pixels does your image contain? How many bytes would be needed to store this image (2) ……………………………………………………………………………………………………………………………………………………………... 27 Digital Images Bitmap graphics store details about every individual element (pixel) of the image and since each pixel could have a different colour, this means an image can be very complex. The file size of a bitmap image can be very large because the computer has to store every pixel. Large bitmap images can take a long time to load or to download from the Internet. When you zoom in to or enlarge a bitmap image, pixelation can occur. This means that the pixels become larger on screen and look like a number of small blocks put together. This is the reason why bitmap images are poor quality when they are enlarged too much Bitmap Image Summary What are they made up of? Pixels What can be edited? Individual Pixels What is the file size Large What happens when you enlarge the image? Pixelation it loses quality Do they look like realistic photographs? Yes Common file formats .BMP .JPEG .GIF .PNG 28 Digital Images VECTOR IMAGES Vector images are not made up of a grid of pixels. Instead vector images store information about the objects that make up an image. These objects are things such as lines, curves and shapes and are represented using mathematical calculations. This means it is possible to edit these objects separately, for example by changing the colour, size or the position of the object. Vector images store details about the shape of individual image objects so they require less storage capacity compared to using pixels. This means they can be saved as smaller files and can be easily edited without loss of quality. Since vector-based images are not made up of a grid of pixels, they can be enlarged and not lose image quality. What are they made up of? Objects and mathematical calculations What can be edited? Individual Objects What is the file size Small What happens when you enlarge the image? It is scalable. It does not lose quality Do they look like realistic photographs? No Common file formats .EPS .PDF .SVG 29 Digital Images IMAGE COMPRESSION Large images can take up a lot of storage space and take a long time to download. Using large file sizes can also be expensive. A user storing the images will have to pay for more storage. A user downloading the images will be charged for the increased data they have to use. To reduce the size of an image file we can use image compression. Compression can be lossless or lossy. Lossless compression means that as the file size is compressed, the picture quality remains the same - it does not get worse. Also, the file can be decompressed to its original quality. PNG PNG is a lossless compression type. It is often used where the graphic might be changed by another person or where the image contains layers of graphics that need to be kept separate from each other. It is high quality. Lossy compression permanently removes data. GIF JPEG JPEG is a lossy compression type. JPEGs are often used for digital camera images because hey have a fairly small file size for the quality that it displays. GIF is a lossy compression type. It compresses images to a maximum 8-bit colour depth, so it isn’t suitable for saving as good quality photos. GIF is often used where transparency is needed on the graphic. GIFs can also be used to store simple animated images as moving image files. GIF 30 Digital Images - Revision Activities 1. What is the name of an individual element of a bitmap image(1) …………………………………………………………………………………………………………………………………………………………………… 2. What are bitmap images also known as? (1) …………………………………………………………………………………………………………………………………………………………………… 3. Describe the difference between bitmap and vector images (2) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… 4. Vector images are described as being scalable. Describe what happens when a vector image is enlarged and what happens when a bitmap image is enlarged (2) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… 5. Define the term image resolution. What is the relationship between image resolution and file size? (3) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… 6. Ruby wants to make a simple moving image. Which file type would be the best choice? Explain your answer (2) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… 7. Describe the difference between lossless and lossy compression. (2) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… 32