The Computer

1. The Computer

2. Simple Interaction: Batch • Computer processing began with batch jobs • A card deck was read into a computer and the job executed until complete • There was no interaction with a job while it was executing • This works well for data processing tasks such as printing bills

3. Interactive Computing • Batch was unsuited for most tasks outside the data processing field • This prompted the development of interactive computing where the user could interact with a task as it ran • This created a need for improved and innovative input devices

4. Text Entry Devices • The keyboard remains the most common input device • It began with the QWERTY layout that legend has it slowed down the typist so that they would not jam the keys on manual typewriters • Other layout, like DVORAK, were designed for higher typing speeds by placing common letters in the middle

5. Text Entry Devices * Wikipedia

6. Repetitive Strain Injury • This is an injury that results from holding the muscles tense for long periods • Affects the muscles, tendons, and nerves • Common with computer users and factory workers • Can be minimized by using ergonomic keyboards

7. Maltron Ergonomic Keyboard * P.C.D. Maltron, Ltd.

8. Phone Pad Entry • Increasingly popular for mobile applications and SMS • Each digit maps to several letters • Letters are entered by clicking digits multiple times to cycle through and select the letter • Incredibly slow method for typing

9. Blackberry Keypad • Devices designed for interactive mobile use have some type of complete keyboard • The RIM Blackberry has a QWERTY keyboard that is operated using the two thumbs

10. Handwriting Recognition • Handwriting recognition has been tried for some mobile devices • It often requires writing is a special way for recognition to work • The technique suffers from inaccuracy • It also has the problem that people write much more slowly than they type

11. Speech Recognition • There is software which can perform speech recognition • It requires at least a pentium processor • It must be trained for one user or use a small vocabulary • Accuracy is about 97% or one mistake every 30 words • It has found application in some automated telephony applications

12. Pointing Devices • Many modern applications require accurate pointing devices • The most common of these is the mouse • Mice usually have one or more buttons to perform an action once the pointer is placed correctly • While mice are common, they are not the best for all applications

13. Touchpads & Eraserheads • Laptops often use touchpads or eraserheads • These have the advantage that they are part of the laptop and do not have to be connected by cables • Many people do not find them as easy to use as mice

14. Trackballs • The trackball is a ball which is moved by the hand • It was more popular before the introduction of the mouse • It is generally considered more difficult to use than a mouse

15. Joystick • The joystick is a stick that detects motion in 2 or 3 dimensions • They are often use for controlling games • They are more natural for certain types of movement • Joysticks can incorporate force feedback to the user creating a more realistic experience

16. Touch Screens • Touch screens can detect when and where the user touches the screen with their finger • They are useful where it is inconvenient to provide another type of input device • They have limited resolution due to the relatively large size of a finger

17. Light Pens • A light pen can be used to point at the screen • The screen detects the point where the pen touches it • This is good for selecting single points • It has been replaced by more modern devices

18. Digitizing Tablets • These are a separate tablet with a pen • Can be used to trace over an existing image to digitize it • Can also be used as an accurate pointing device • This works because people are better at fine motion with a pen that with a mouse

19. Eyetracking • Some systems track eye movements with a low powered laser • This means that all you have to do is look at a portion of the screen • Has been used in some military applications • Useful in UI research to see what the user looks like • Not a mainstream input device

20. Display Devices • Most computers would be useless without some sort of display capability • The two types are • Bitmapped display • Vector displays • Almost all displays in use today are bitmapped

21. Vector Displays • This is a display which draws vectors • If a 45 degree line is needed, then one is drawn by the hardware • This produces accurate lines • These displays are slow and prone to flicker • They have been replaced by bitmapped displays

22. Bitmapped Displays • Bitmapped displays are composed of pixels, which can be displayed in different colors • Images are drawn into video memory which is then displayed on the screen • Most screens have a resolution of about 100 pixels per inch

23. Cathode Ray Tubes • The CRT is television technology where an electron beam is scanned across a phosphor screen • When the beam is on, the phosphor glows • Each pixel is made of 3 different colored phosphors to create a color image • CRT technology is both fast and cheap • It can suffer from flicker and interlacing is used to alleviate this by drawing alternate lines on every scan cycle

24. CRT Health Risks • Although health risks of CRTs have never been proven, potential dangers include • Xrays, mostly from the back • Small amounts of UV & IR from the phosphor • RF emissions & 16KHz sound • Electromagnetic fields

25. Liquid Crystal Displays • CRTs are being replaced by LCDs • These have a crystal sandwiched between two layers of glass • The top layer is polarized and the bottom layer is reflective • The crystal is then polarized one way or the other by the application of current • LCDs are slower than CRTs although this has improved • LCDs cause less eye strain due to lower flicker • LCDs have fewer emissions

26. Digital Paper • This is an emerging technology where a thin flexible plastic sheet can be used as a display • This promises portability and the ease of use of paper • It is already being used in initial versions of electronic books

27. Virtual Reality • VR systems create an artificial world with which the user can interact • This can be as simple as a PC display or can immerse the user in the environment with VR goggles • Since the environment is 3-D, it requires the use of 3-D input devices

28. 3-D Input Devices • The 3-D mouse is often called a bat • It has 6 degrees of freedom • X,Y,Z position • Up/Down direction, left/right orientation, twisting about its own axis • A dataglove has sensors to track hand and finger motion • It can be used to directly manipulate items in a 3-D world

29. 3-D Input Devices • Virtual reality helmets can • display different scenes to each eye to create depth • Can track head and eye position • Suits can be used for whole body tracking so that all of your movements can have an effect on the virtual world

30. Printing • Many people still prefer to see output on paper • Modern printers are very capable of producing high-quality output at a rapid pace • The current generation of printers are of two main types

31. Printer Types • Laser printers • Fast, high-quality text (1200 DPI) • Monochrome or color • Relatively poor graphics • Inexpensive • Ink Jets • Slower, full color, about 1440 DPI • Photo quality graphics • Expensive to operate

32. Fonts • A wide variety of fonts have been created since the invention of the printing press • They fall into several categories • Fixed-pitch • Courier is a fixed pitch font in which all letters are of the same width

33. Fonts • Proportional fonts • This is a proportional or variable pitch font where each letter is a different width. These fonts are high quality and easier to read • Serif fonts • Times Roman is one of the most popular fonts and is an example of a serif font. Each letter has small decorations called serifs that help the eye follow the line. This reduces eye strain and makes reading faster.

34. Fonts • Sans serif fonts • Arial is a font without serifs. Sans serif fonts are harder to read for text but are often used for headings to make them stand out. • Cursive fonts • These look like handwriting and are largely used for decorative purposes. They are often difficult to read.

35. Readability • Variable pitch is easier to read than fixed • Serif fonts are better for the text of a document • Serif fonts only work well on high resolution displays • Words in lower case are easier to READ THAN WORDS ALL IN UPPER CASE • Some text, such as flight numbers, are easier with capitals that with lower case • BA793 vs. ba793

36. Scanners • Scanners take input from paper and convert it to electronic form • They scan a bitmapped image • Optical character recognition can be performed on the bitmap to turn it into text • Images are retained as bitmaps

37. Computer Memory • Computer memory is broken into two types • Short-term, high speed RAM • Used for temporary storage • Limited capacity • Long term, slower disk • Used for long term storage • Massive capacity

38. Processor Speed • PC processor speed is in the range of 100 MIPS • Even this speed can result in delays • When dragging the mouse people will overshoot the target if the pointer does not keep up • When clicking or typing input is buffered and the user might give instructions twice if the computer appears not to have received a command. The computer will do something twice as it works its way through buffered commands • Computer performance can be limited by several factors • Computation, storage, graphics, and network

39. Computation Bound • The CPU speed is the limiting factor • Users expect • Simple operations to be quick • Long operations to be slower • Therefore, if an operation will take longer than the user expects, indicate this in some way (NOTE: This might take a few seconds)

40. Computation Bound • Users do not like the computer to just sit there while working on a long operation • They wonder if the machine has crashed and will sometimes interrupt it • During long running operations you should • Change the cursor to a watch • Show a progress bar

41. Storage Bound • If storage access is the bottleneck • Don’t fetch data until it is needed • If there is excess processor speed • Compress data in storage to reduce the amount to transfer and have the CPU decompress • Have the CPU recalculate data rather than store and retrieve the data

42. Graphics Bound • This is increasingly the bottleneck in • Image manipulation programs • Games • 3-D environments • Performance can be increased by • Recoding with faster algorithms • Using faster graphics cards which perform more operations in hardware

43. Network Bound • Network speed often limits the nature or quality of the services which can be provided • Audio might have to be lowered in quality • Video might need to use lower resolution or lower frame rate • Network speed should be monitored so that the user can be advised if delays are to be expected

44. Predictable Performance • Users like predictability • They expect the same or similar operations to take the same time every time • If this is not so, they get frustrated • To gain predictability • Use data structures which give the same performance for every query • Notify the users if a query will take longer than expected • Display a progress bar if an operation takes more than 1 second