ICT Study Notes PDF

Chapter 1 1.1 Information system Purpose - for automating processes, reducing human error and improving efficiency - Functions - hardware - 1. Processing - Central processing unit (CPU) 2. Connection of system units - motherboard 3. Network communication - Home router, switch, bluetooth U...

Chapter 1 1.1 Information system Purpose - for automating processes, reducing human error and improving efficiency - Functions - hardware - 1. Processing - Central processing unit (CPU) 2. Connection of system units - motherboard 3. Network communication - Home router, switch, bluetooth USB dongle 4. Input - microphone, keyboard, barcode scanner 5. Output - speaker, monitor, information panel in a restaurant Process - a series of steps to make sure the data can achieve the purpose precisely 1.2 Data information Data - a collection of unorganized facts which usually has no meaning on its own Information - after processing data, it is put into context and converted to information Input process output cycle - 1. Data is input 2. Computer processes data 3. Meaningful data is output from computer Text - character such as numbers, letters, symbols etc, when stored in a computer they are repeated by a character encoding system 2 types of text - plain text (characters only) and formatted text (font type, size, colors etc) Image - digital images are images captured by digital cameras or made with images editing software 2 types of images - bitmap (pixels) and Vector (stored as mathematical formulae) Advantages of bitmap - real life digital photos are usually bitmap - It can be edited by common editing softwares Advantages of vector - File size is smaller - Doesn’t have rough edges and will not become blurry when zoomed in  Audios - data that can be converted to sounds Videos - combination of images and audios ( have larger file sizes so they are usually stored as compressed files) 1.3 Information processing Information processing converts raw data into meaningful data, there are 7 stages Collection -> organization -> storage -> processing -> analysis -> transmission -> presentation Data collection - can be collected by various methods like observation, experiments, interviews, surveys etc To collect data efficiently, we have to consider the scope and the data Different approaches are used for different scopes Different approaches are used for different data types Organization - managing and classifying the collected data in a specific way Storage - after organization data is stored so it can be retrieved and processed anytime (data can be stored as physical copies or in a digital storage like hard disks, USB flash drives etc) Processing - editing, modifying and updating data Analysis - extracting meaningful information from processed data Presentation - the output of data through different medias 1.4 information age With rapid development of ICT, the internet has improved constantly Causes - prices of computer components are more affordable so personal computers and phones have become more widespread Application design - allows people to access desired information directly Communication network - invention of optical fibers and the advantage of telecommunication Internet of things - the network of physical objects Big data - large amounts of data gathered from high usage of digital devices, once processed and analyzed it can show as various valuable information  Chapter 2 2.1 data hierarchy Data is usually stored in a hierarchical form. Every higher level of data is a collection of items from the lower levels Level - description - Field - stores specific attribute of an entity - Record - collection of fields about an entity - File (table) - collection of records sharing the same record structure - Database - a collection of related files 2.2 data control Errors that may occur during data input - Data source error - wrong data is provided by data source - Transcription error - data is misread, misheard or mistyped - Transposition error - incorrect placement of data When incorrect data is input, the output data will not be useful, this is called “garbage in, garbage out” To reduce error, data control should be applied (data validation, data verification) Data validation (done by computers) - Presence check - must have data in required fields - Fixed value check - data can only be selected from a list of specific values - Type check - data must be a certain type - Range check - data must be within a certain range - Length check - data must be within a certain length - Format check - data must be in a specific format - Consistency check - data must be reasonable when compared to data in other fields - Uniqueness check - data must be unique for the field Data verification (done by humans) - Inputting data twice - input the same data twice - Double data entry - input the same data separately - Proofreading data - compare input data against the original document Data types - Integer - numbers that are positive and negative - Float - numbers that are positive and negative that have a decimal point - String/text - characters of any language or symbols - Boolean - true or false  2.3 functions of database Organization - the data in a database is organized according to the database structure Storage - inserts new records into a database Retrieval - retrieve specific data from a database by using Structured Query Language (SQL) or Graphical User Interface (GUI) 2.4 file access method Data can be stored in different storage devices, the storage device determines how the data is accessed Two common file access methods - sequential access and direct access Sequential access - data is written sequentially, the computer needs to search through the storage from top to bottom (only used by Magnetic Tape) Direct access - data can be written in any storage position, data can be directly accessed (used by hard disk, USB flash drive, optical disk, floppy disk) Chapter 3 3.1 number system and representation decimal system - usually used by people for counting binary system - usually used by digital devices to store data in bits Unit of data - Bit - the most basic unit of data. - Byte - 1B = 8 bits - Kilobyte - 1KB = 1024 B - Megabyte - 1MB = 1024KB - Gigabyte - 1GB = 1024MB - Terabyte - 1TB = 1024GB Bitrate / data transfer rate : the amount of data transferred per unit time in data transmission system - Bit per second(bps) - one bit of data is transferred every second - Kilobit per second(kbps) - 1 kbps = 1000 bps - Megabit per second(mbps) - 1 mbps = 1000 kbps - Gigabit per second(gbps) - 1 gbps = 1000 mbps - Terabit per second(tbps) - 1 tbps = 1000 gbps Units of data - usually binary based , units of bitrate - usually decimal based Binary number - ‘0’ and ‘1’  Decimal number or denary number - 0,1,2,3,4,5,6,7,8,9 Decimal: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Hexadecimal: 1 2 3 4 5 6 7 8 9 A B C D E F (after F there’s no more) Unsigned integers - integers that don’t have a negative sign (positive integers and 0) Two’s complement - Binary numbers that start with 0 = positive - Binary numbers that start with 1 = negative Overflow errors - occurs when result of calculations is out of range, thus results will be wrong 3.2 Character encoding English - American Standard Code for Information Exchange (ASCII) Characteristics of ASCII - Digits are arranged in ascending order(small to big) - Upper case and lower case letters are arranged in alphabetical order There are two sets of chinese characters - Traditional chinese - Big-5 code - Simplified chinese - Guobiao code - both use 2 bytes (16 bits) to store and contain over 10k characters - traditional code does not share the same code as simplified code Unicode - character encoding system which represents multiple languages - used to represent all existing languages - due to the large number of unicode characters, it may use up to 4 bytes, depending on the language 3.3 Barcode encoding  barcode - Consists of bars and spaces of different widths to represent a text string - Reduces typing error and input time Scanning a barcode - only area covered by the red line (from scanner) is scanned , so the height of the bars don't matter , only width and space matters A readable barcode must Have enough space for the quiet zone and keep the widths of its bars and spaces unchanged Barcode - Normally can only be scanned at 0° or 180° - If width of a single bar is altered, the code cannot be scanned - Some can represent ASCII while some can only represent numbers - Maximum character limit : 50 QR code - Can be scanned from any direction - Has high correction capability, can often restore up to 30% of data - Can represent unicode characters - Usual character limit is more than 1000 QR codes can still be scanned even if - It is rotated - Distorted - Dirtied - Coloured  - Multicolored - Obstructed by a logo (This shows how high the error correction capability a QR code has is) 3.4 analog and digital data Analog Data - represented in a physical way with continuous values (soundwaves , written text etc.) (Stored in photographic films and cassette tapes) Digital data - represented in discrete symbols (‘0’ and ‘1’), usually stored in devices (digital photos etc) (Stored in memory cards and optical disc) 3.5 multimedia Multimedia can be stored in various file formats and have different attributes Most of the time, the file Format is indicated by its file extension (.txt ,.png etc) Compression - since Multimedia files tend to have a larger size, they are usually compressed to allow file transmission and save storage Lossless compression - no data is lost after compression (common Compressed file formats : ZIP , RAR , 7Z) Lossy compression - some data Is lost after compression but lossy compression saves more storage space than lossless compression Compression ratio : uncompressed size / compressed size File size calculation : file size per character x number of characters File formats for plain text - TXT - small file size , widely supported by different operating systems File formats for formatted texts - DOC/DOCX - ODT - Pages - PDF An image file has 4 important attributes : resolution, color depth, aspect ratio, transparency  Color Depth - number of bits used to represent the color of a pixel High resolution - clear and detailed (vector) Low resolution - pixels (bitmap) Aspect ratio - ratio of width to height Transparency - whether the image can be / have transparent Areas or not 3 important attribute of audios - bit depth - sampling rate - the number of channels Bit depth - number of bits used to represent an audio sample, the higher the bit depth, the more sound levels it can represent and better the quality High bit depth = 50 levels between -100 and 150 medium bit depth = 25 levels Low bit depth = 10 levels Sampling rate - number of audio samples taken per second Higher sampling rates means the audio is closer To the original soundwave and better quality Number of channels - sometimes an audio file has more than one channel (stereo audio has 2 channels while 5.1 surround sound has more than 2)