The Computer Lec (3) PDF

The Computer Lec (3) Dania Mohamed Ahmed  Introduction To fully grasp human-computer interaction, it's essential to understand both humans and computers. The previous lecture discussed human capabilities and behavior relevant to this in...

The Computer Lec (3) Dania Mohamed Ahmed  Introduction To fully grasp human-computer interaction, it's essential to understand both humans and computers. The previous lecture discussed human capabilities and behavior relevant to this interaction, while this lecture focuses on computers and their input- output devices, examining how technology affects the interaction and interface style. When we interact with computers, our goal is similar to interacting with other people: transferring information. In human interactions, we exchange information back and forth, often responding to what was recently communicated. This same principle applies to computers, where interaction involves the transfer of information between the user and the computer, and vice versa.  A typical computer system Consider a typical computer setup as shown in Figure. A typical computer setup includes a computer box, a keyboard, a mouse, and a color screen, with the screen layout shown alongside. These devices influence the interface characteristics. Variations exist based on hardware configurations, such as desktops, laptops, and PDAs (personal digital assistants). window 1 window 2 12-37pm  The Computer A computer system is made up of various elements. each of these elements affects the interaction input devices – text entry and pointing output devices – screen, digital paper virtual reality – special interaction and display devices physical interaction – e.g. sound, haptic, bio-sensing paper – as output (print) and input (scan) memory – RAM & permanent media, capacity & access processing – speed of processing, networks  Text Entry Devices keyboards (QWERTY et al.) Chord keyboards Phone pad and T9 entry Handwriting recognition Speech recognition  Keyboards Most common text input device Allows rapid entry of text by experienced users Keypress closes connection, causing a character code to be sent Usually connected by cable, but can be wireless  The QWERTY keyboard While the layout of letters and digits on a QWERTY keyboard is fixed, non-alphanumeric keys can vary between keyboards. For instance, British keyboards have the pound sign (£) above the 3, while American keyboards have the dollar sign ($). There are also variations in the placement of brackets, backslashes, and other symbols. Additionally, different national keyboards may include accented letters, and the traditional French layout, known as AZERTY, places the main letters differently from the standard QWERTY layout. 1 2 3 4 5 6 7 8 9 0 Q W E R T Y U I O P A S D F G H J K L Z X C V B N M ,. SPACE  Alternative Keyboard Layouts Alphabetic keys arranged in alphabetic order not faster for trained typists not faster for beginners either! Dvorak common letters under dominant fingers biased towards right hand common combinations of letters alternate between hands 10-15% improvement in speed and reduction in fatigue But - large social base of QWERTY typists produce market pressures not to change.  Chord keyboards Chord keyboards differ greatly from normal alphanumeric keyboards, using only a few keys (four or five) where letters are produced by pressing one or more keys simultaneously. For example, the Microwriter uses keypress patterns that reflect letter shapes. These keyboards are compact, easier to learn, and can achieve fast typing speeds. They are also suitable for one-handed use and in confined spaces. Despite their advantages, chord keyboards are unlikely to become mainstream due to lack of familiarity but have niche applications. Chord keyboards  phone pad and T9 entry Use numeric keys with multiple presses ⁃ 2–abc 6-mno ⁃ 3-def 7-pqrs ⁃ 4-ghi 8-tuv ⁃ 5-jkl 9-wxyz hello = 4433555[pause]555666 surprisingly fast!  Handwriting recognition Handwriting is a familiar text entry method, but converting it to digital text is challenging. The technology struggles with accuracy and individual differences in handwriting. Effective recognition requires capturing how letters are drawn, not just their shapes. Online recognition, which tracks stroke data in real-time, is more effective than analyzing handwritten text on paper. The shape of letters can vary significantly depending on the surrounding words, complicating recognition.  Speech recognition Speech recognition offers a promising method for text entry but is still limited in its use. Its appeal lies in the intuitive nature of interacting through speech. Challenges include understanding natural language's vagueness, imprecision, and pauses. Unique speech patterns require individual system training, and factors like accents, colds, emotions, and background noise can affect performance. Despite these issues, speech technology is used in specific areas like telephone information systems, accessibility for disabled individuals, hands-occupied scenarios (e.g., military), and for users with repetitive strain injuries (RSI). It can either replace keyboards in existing systems or be integrated into new systems designed to exploit its benefits while addressing its limitations.  Numeric keypads For entering numbers quickly: calculator, PC keyboard For telephones 1 2 3 7 8 9 not the same!! 4 5 6 4 5 6 ATM like phone 7 8 9 1 2 3 0 # 0. = * telephone calculator  Positioning, Pointing And Drawing Pointing devices are crucial in modern computing, especially in computer-aided design (CAD) for positioning and drawing. They allow users to point, position, and select items on the screen, either directly or via a pointer. Drawing with a mouse requires different skills compared to a pencil. While the mouse is the most common pointing device for desktop computers, it faces competition from touchpads and other devices due to the rise in laptops and handheld computing devices. Other pointing devices include trackballs, joysticks, touch screens, tablets, eye gaze systems, and cursors.  The Mouse The mouse has become a major component of the majority of desktop computer systems, and is the little box with the tail connecting it to the machine in our basic computer system picture. The mouse moves a pointer on the screen, called the cursor, with the box as the body and the wire as the tail, hence the name "mouse". Two characteristics: 1. planar movement 2. Buttons (usually from 1 to 3 buttons on top, used for making a selection, indicating an option, or to initiate drawing etc.) Mouse located on desktop requires physical space and no arm fatigu Although most mice are hand-operated, not all are – there have been experiments with a device called the footmouse. As the name implies, it is a foot-operated device. The cursor is moved by foot pressure on one side or the other of a pad. This allows one to dedicate hands to the keyboard. A rare device, the foot mouse has not found common acceptance  Touchpad Touchpads are touch-sensitive tablets usually around 2–3 inches (50–75 mm) square. They were first used extensively in Apple Powerbook portable computers but are now used in many other notebook computers and can be obtained separately to replace the mouse on the desktop. They are operated by stroking a finger over their surface, rather like using a simulated trackball. The feel is very different from other input devices ‘stroke’ to move mouse pointer Good ‘acceleration’ settings important 1. fast stroke 2. slow stroke  Trackball and thumbwheel The trackball functions as an inverted mouse with a weighted ball that rotates within a static housing, detecting motion to move the cursor. It is compact and doesn't require additional operating space, using separate buttons for selection. Although fairly accurate, it is less effective for drawing due to difficulty with long movements. Trackballs come in various sizes, impacting usability based on their size, weight, rolling resistance, and texture. They are popular in video games for their responsive behavior and the ability to spin the ball quickly. Thumbwheels, featuring two orthogonal dials for cursor control, are inexpensive but slow and limited to horizontal or vertical movement, which can be useful in specific applications.  Joystick and keyboard nipple The joystick is an indirect input device, taking up very little space. Consisting of a small palm-sized box with a stick or shaped grip sticking up from it, the joystick is a simple device with which movements of the stick cause a corresponding movement of the screen cursor. Indirect: pressure of stick = velocity of movement Buttons for selection on top or on front like a trigger Often used for computer games aircraft controls and 3D navigation  Touch-sensitive screens (touchscreens) Touchscreens provide a direct method for pointing and selecting objects on the screen by detecting a user's finger or stylus. They operate through various technologies, such as interrupting light beams, detecting capacitance changes, or using ultrasonic reflections. Touchscreens offer fast, direct interaction with no need for a separate pointing device, making them ideal for menu selections. The screen serves as both input and output, reducing the risk of damage from dirt. Disadvantages include potential greasy marks from fingers and reduced accuracy for small or precise selections and drawing.  Stylus and light pen Stylus  small pen-like pointer to draw directly on screen  may use touch sensitive surface or magnetic detection  used in PDA, tablets PCs and drawing tables Light Pen  now rarely used  uses light from screen to detect location BOTH …  very direct and obvious to use  but can obscure screen  Digitizing tablet The digitizing tablet is a more specialized device typically used for freehand drawing, but may also be used as a mouse substitute. Some highly accurate tablets, usually using a puck (a mouse-like device), are used in special applications such as digitizing information for maps. It can also be used for text input; if supported by character recognition software, handwriting can be interpreted. Problems with digitizing tablets are that they require a large amount of desk space, and may be awkward to use if displaced to one side by the keyboard.  Eyegaze Eyegaze systems control the computer by detecting where you look, using either special glasses, a head-mounted box, or built-in sensors on or below the screen. They work by shining a low-power laser into the eye and tracking reflections from the retina to determine eye direction. Eyegaze systems are fast and accurate but can be costly, with high-end versions being particularly expensive. They are effective for selection but not suitable for drawing due to the lack of smooth eye movement. Distinguishing intentional gazing from accidental glances can be challenging in practical applications.  Cursor keys Four keys (up, down, left, right) on keyboard. Very, very cheap, but slow. Useful for not much more than basic motion for text-editing tasks. No standardised layout, but inverted “T”, most common  Discrete Positioning Control In phones, TV controls etc. cursor pads or mini-joysticks discrete left-right, up-down mainly for menu selection  Display Devices Bitmap screens (CRT & LCD) Large displays and situated displays Digital paper  Bitmap Displays Virtually all computer displays are based on some sort of bitmap. That is the display is made of vast numbers of colored dots or pixels in a rectangular grid. These pixels may be limited to black and white (for example, the small display on many TV remote controls), in grayscale, or full color. Screen is vast number of coloured dots. That more bits per pixel allow for more color or intensity possibilities. For instance, 8 bits per pixel can display =256 colors. The colormap, which defines these colors, can be changed to display different colors, although not all at once. Modern desktop computers typically use 24 or 32 bits per pixel for virtually unlimited colors, while devices like mobile phones and PDAs often have limited color ranges or are monochrome.  Bitmap Displays Cont.. As well as the number of colors that can be displayed at each pixel, the other important measure is the screen's resolution.The word ‘resolution’ is used in a confused (and confusing!) way for screens. Display devices like monitors and LCD screens can have a maximum resolution, but the computer might send a lower resolution. For example, a screen with a 1200 × 900 resolution at 96 pixels per inch might only receive an 800 × 600 signal from the computer. On a CRT, this results in a stretched image with a lower pixel density. An LCD screen, which cannot change its pixel size, would maintain its pixel density and add a black border to accommodate the lower resolution. LCD projectors may try to adjust the image, causing display artifacts like stretched or squashed pixels, leading to visual issues such as disappearing thin lines or uneven line thickness.  Health hints … do not sit too close to the screen do not use very small fonts do not look at the screen for long periods without a break do not place the screen directly in front of a bright window work in well-lit surroundings Take extra care if pregnant. but also posture, ergonomics, stress  Liquid crystal displays Smaller, lighter, and … no radiation problems. Found on PDAs, portables and notebooks, and increasingly on desktop and even for home TV also used in dedicted displays: digital watches, mobile phones, HiFi controls How it works … Top plate transparent and polarised, bottom plate reflecting. Light passes through top plate and crystal, and reflects back to eye. Voltage applied to crystal changes polarisation and hence colour N.B. light reflected not emitted => less eye strain  large displays There are several types of large screen display. Some use gas plasma technology to create large flat bitmap displays. These behave just like a normal screen except they are big and usually have the HDTV (high definition television) wide screen format which has an aspect ratio of 16:9 instead of the 4:3 on traditional TV and monitors. As well as for lectures and meetings, display screens can be used in various public places to offer information. These may be large screens where several people are expected to view or interact simultaneously, or they may be very small.  Digital paper A new form of ‘display’ that is still in its infancy is the various forms of digital paper. These are thin flexible materials that can be written to electronically, just like a computer screen, but which keep their contents even when removed from any electrical supply. As the technology matures, the aim is to have programmable sheets of paper that you attach to your computer to get a ‘soft’ printout that can later be changed.  Physical Controls and Sensors Sound, touch, feel, smell Physical controls Environmental and bio-sensing  Sound output Auditory signals are another mode of output, often used alongside screen displays, but their effectiveness and optimal usage are not yet fully understood. Sounds like beeps, clanks, and whistles provide system feedback and are important for interactive systems. Examples include keyboards emitting clicks to improve performance and telephone keypads producing distinct tones for key presses, indicating successful input and providing key-specific information.  Touch, feel and smell In typical computer applications, other senses are less utilized, but computer games often use haptic devices like joysticks and steering wheels with force feedback to simulate actions (e.g., a car going off track). Haptic devices provide varying resistance and sensations, enhancing physical interaction but requiring careful control due to their rapid responses. Texture perception is challenging because it relies on detecting small changes on the skin, and technology for this is still emerging. A smell can evoke strong memories, and some arcade games use scent generators (e.g., burning rubber for racing games). These devices, which release scents from tiny capsules, are not yet mass-market but hold potential for future expansion.  physical controls Desktop computers use generic keys and controls to serve multiple functions, while dedicated control panels are designed for specific devices and single uses, leading to significant differences in design. Microwave ovens, for instance, have flat plastic control panels with buttons that slightly depress when pressed. This design choice enhances the appliance's appearance and practical usability, especially in a kitchen environment where hands may be greasy or dirty, helping to prevent food buildup and maintain cleanliness.  physical controls easy-clean smooth buttons  Environment and bio-sensing Public washrooms often use sensor-based controls, such as infrared sensors that activate water flow when hands are placed under the faucet. Similarly, automatic car courtesy lights turn on when the door is opened. Sensors are widely used in various environments for tasks like controlling automatic doors, energy-saving lights, and monitoring behavior (e.g., security tags in shops). Different types of sensors are available to measure a wide range of variables, including temperature, movement (e.g., ultrasound, infrared), location (e.g., GPS), and weight (e.g., pressure sensors).  Paper: Printing And Scanning Print technology Fonts, page description, WYSIWYG Scanning, OCR  Printing Popular printing technologies use dots to create images on paper. The quality of the print depends on dot resolution, measured in dots per inch (dpi). dpi can be visualized as a grid on graph paper; more lines per inch mean higher resolution. Factors that can affect print quality include dot size, the sequential nature of printhead operations, and offset printheads. The critical features of printing technologies: 1. Resolution: Refers to the clarity of the print, determined by the number of dots per inch (dpi). 2. Size and Spacing of the Dots: Influences the quality and detail of the printed image. 3. Speed: Typically measured in pages per minute (ppm), indicating how quickly a printer can produce prints. 4. Cost: Includes the initial purchase price, maintenance, and operational costs of the printer.  Types of Printers 1. Inkjet Printers: Ideal for home use and small offices, inkjet printers spray tiny droplets of ink onto paper. They are known for high-quality photo prints and versatility in printing on various media types. 2. Laser Printers: Common in offices, laser printers use a laser beam to produce high- speed, high-volume prints with sharp text and graphics. They are cost-effective for large quantities of black-and-white documents. 3. Dot Matrix Printers: These impact printers are used for specific tasks like printing multipart forms and receipts. They work by striking an ink-soaked ribbon against the paper.  Fonts Font – the particular style of text Courier font Helvetica font Palatino font Times Roman font §´µº¿Â Ä¿~ (special symbol) Size of a font measured in points (1 pt about 1/72”) related to its height This is ten point Helvetica This is twelve point This is fourteen point This is eighteen point and this is twenty-four point  Fonts Cont.. Pitch fixed-pitch – every character has the same width e.g. Courier variable-pitched – some characters wider e.g. Times Roman – compare the ‘i’ and the “m” Serif or Sans-serif sans-serif – square-ended strokes e.g. Helvetica serif – with splayed ends (such as) e.g. Times Roman or Palatino  Readability of text lowercase easy to read shape of words UPPERCASE better for individual letters and non-words e.g. flight numbers: BA793 vs. ba793 serif fonts helps your eye on long lines of printed text but sans serif often better on screen  Page Description Languages Page Description Languages (PDLs) are specialized programming languages used to describe the layout, content, and appearance of printed or displayed pages. They are essential in desktop publishing, printing, and digital document creation, enabling precise control over text, graphics, and images. PDLs ensure that documents maintain consistent formatting and appearance across different devices and platforms. Examples include PostScript and PDF for high-quality printing and document exchange, HTML and XHTML for web content, and PCL for controlling printers. By defining the structure and style of a page, PDLs play a crucial role in both digital and print media (PostScript is the most common).  Scanners A scanner is a device that transforms physical objects like documents, photos, or artwork into digital images. It's commonly used for digitizing materials for storage, sharing, or editing. Types of Scanners: 1. Flatbed Scanners: Description: These scanners have a flat glass surface where the item to be scanned is placed. Uses: Best for scanning documents, books, and photos. Advantages: Provides high-quality scans and can handle various media sizes and types. 2. Handheld Scanners: Description: Portable devices that you manually move over the document or image. Uses: Ideal for scanning large-format documents or books, especially where a flatbed scanner isn't feasible. Advantages: Portable and easy to use in different locations.  Applications of Scanners Document Management: Digitizing paper documents for electronic storage minimizes physical storage and enhances retrieval. Archiving and Preservation: Converts historical documents, photographs, and artworks into digital formats for long-term preservation. Graphic Design and Publishing: Scans images and artwork for use in digital media, print, and online publications. Medical Imaging: Digitizes medical records, X-rays, and diagnostic images for electronic health records (EHR) and analysis. Education: Scans textbooks, notes, and educational materials for digital distribution and increased accessibility.  Memory Short term and long term Speed, capacity, compression Formats  Short-term Memory - RAM Random Access Memory (RAM) is a crucial component in computing, serving as the short-term memory of a computer. It temporarily stores data that the CPU (central processing unit) needs to access quickly (100 nano-second access time). Key Characteristics of RAM: 1. Volatile Memory: RAM loses its data when the power is turned off (Data stored in RAM is temporary and used for active processes) 2. Speed: RAM is much faster than other types of storage. 3. Capacity: Measured in gigabytes (GB) or terabytes (TB). (Typical desktop computers 64 to 256 Mbytes RAM)  Long-term Memory - disks Provided by magnetic and optical disks for persistent data storage. Retains information even when the computer is powered off. Ideal for storing large amounts of data, including documents, applications, and system files. Magnetic Disks:  Use magnetic storage techniques to record data.  Commonly used in hard disk drives (HDDs).  A staple in computer storage for decades.  Offers high capacity and cost-effective storage, suitable for everyday use and large data needs. Optical Disks:  Use laser technology to read and write data.  Common types include CDs, DVDs, and Blu-ray discs.  Ideal for media distribution, backups, and archiving due to their durability and longevity.  Generally offer less capacity compared to magnetic disks.  Speed and Capacity Speed refers to how quickly data can be read from or written to a storage medium. Capacity refers to the amount of data that can be stored on a storage medium, typically measured in gigabytes (GB) or terabytes (TB). some sizes (all uncompressed):  this book, text only ~ 320,000 words, 2Mb  the Bible ~ 4.5 Mbytes  digital photo ~ 10 Mbytes (2–4 mega pixels, 24 bit colour)  video ~ 10 Mbytes per second (512x512, 12 bit colour, 25 frames per sec)  Compression Compression is the process of reducing the size of a file or data stream. This is achieved by encoding the information more efficiently, which helps save storage space and reduces the time required to transmit the data. Compression can be broadly categorized into two types: lossless and lossy. Lossless compression reduces the file size without any loss of information. When decompressed, the original data is perfectly reconstructed. Lossy compression reduces file size by removing some of the data, typically those parts considered less important. When decompressed, the original data is only approximated, not perfectly reconstructed. Purpose of compression: 1. To reduce file size. 2. To save storage space. 3. To speed up data transfer.  Storage formats - text Text storage formats are essential for representing, storing, and exchanging textual information across various digital platforms. These formats can range from simple plain text files to more complex structured documents that include formatting, metadata, and other attributes. Common Text Storage Formats: 1. Plain Text (.txt): the simplest text storage format, containing only unformatted text 2. Rich Text Format (.rtf): a cross-platform text format that includes basic formatting options like bold, italics, and different fonts. 3. HyperText Markup Language (.html): the standard language for creating web pages, containing text along with tags for formatting, links, and multimedia 4. Portable Document Format (.pdf): a versatile file format that preserves the formatting of a document, regardless of the device or software used to view it.  Storage formats - media Image Formats: 1. Joint Photographic Experts Group (JPEG/JPG) 2. Portable Network Graphics (PNG) 3. Graphics Interchange Format (GIF) Audio Formats: 1. MP3 (MPEG-1 Audio Layer 3) 2. WAV (Waveform Audio File Format) Video Formats: 1. MP4 (MPEG-4 Part 14) 2. AVI (Audio Video Interleave)  Processing and Networks Finite Speed Limits Of Interaction Networked Computing  Finite processing speed Processing speed impacts the user interface, with two types of faults based on whether processing is too slow or too fast. 1. Faults Due to Slow Processing: Example: A system fails to draw lines accurately if the mouse movement isn’t promptly registered after a button press. Impact: Results in incorrect line drawing if the user moves the mouse before the system captures the starting position. Solution: Buffer user input to remember keystrokes and mouse actions. Issue with Buffering: Delayed feedback can lead to unexpected behaviors, such as cursor lag in text editors, where the cursor overshoots its intended position.  Finite processing speed Cont.. 2. Faults Due to Fast Processing: Example: Delays in menu or icon responses may cause users to click multiple times, resulting in all buffered clicks being processed at once. Impact: Creates chaotic screen behavior with a flurry of flashing windows and menus. Cause: Variability in response times, often due to delays in swapping programs in and out of main memory. Summary:  Slow Processing Faults: Often involve delayed feedback and buffering issues.  Fast Processing Faults: Include erratic system behavior due to sudden processing of multiple buffered actions.  Networked computing Networked computing involves connecting multiple computers and devices through a network, enabling them to communicate, share resources, and perform tasks collaboratively. This interconnected system allows for greater flexibility, efficiency, and scalability in both personal and enterprise computing environments. Benefits 1. Resource Sharing: Allows users to share hardware (like printers) and software resources, reducing costs. 2. Improved Communication: Facilitates seamless communication and collaboration among users, regardless of their physical location. 3. Scalability: Enables easy expansion of networks to accommodate more users and devices. 4. Flexibility: Provides access to data and applications from various devices and locations, enhancing mobility and productivity.  The internet The Internet is a global network linking several private, public, academic, business, and government networks. It supports information exchange, communication, and access to a wide range of resources and services. Emerging from 1960s research projects, the internet has become crucial to daily life, allowing for activities like browsing websites, sending emails, streaming media, and social networking. Common language (protocols): 1. HTTP (HyperText Transfer Protocol): used for transferring web pages on the World Wide Web. 2. HTTPS (HyperText Transfer Protocol Secure): a secure version of HTTP. 3. TCP/IP (Transmission Control Protocol/Internet Protocol): the fundamental protocol suite for internet communication. 4. FTP (File Transfer Protocol): used for transferring files between computers on a network. 5. SMTP (Simple Mail Transfer Protocol): used for sending emails. 6. DNS (Domain Name System): translates human-readable domain names into IP addresses.