The Computer and Human-Computer Interaction

These flashcards cover computer system elements, input/output devices, display technologies, memory types, and network protocols based on modern Human-Computer Interaction principles.

Input devices

Elements of a computer system used for text entry and pointing, such as keyboards and mice.

Batch processing

An older computing method involving prepared punched card stacks or large data files, characterized by long wait times and line printer output.

Interactive computing

Modern computing characterized by rapid feedback where the user is in control and engaged in "doing rather than thinking."

QWERTY

A standardized keyboard layout originally designed to prevent mechanical typewriters from jamming; it is not the optimal arrangement for typing speed.

Dvorak layout

An alternative keyboard layout that places common letters under dominant fingers and alternates hands for common combinations, resulting in a $10$-$15\%$ improvement in speed.

Chord keyboards

Keyboards where four or five keys are pressed in combinations to type letters; they are compact and fast but require training and can cause fatigue.

T9 predictive entry

An entry method for phone pads that uses a dictionary to "guess" the correct word from a single key press per letter, such as typing $43556$ for "hello."

Handwriting recognition

A method of inputting text using a pen and digitizing tablet, which must overcome technical problems like segmenting joined-up writing and interpreting different styles.

Speech recognition

An input method that is most successful with a single user and limited vocabulary but faces challenges from external noise and imprecise pronunciation.

Mechanical mouse

A pointing device that detects motion via a ball on the underside that rotates orthogonal potentiometers.

Optical mouse

A pointing device that uses a light emitting diode to detect alterations in reflected light intensity to calculate relative motion in the $(x, z)$ plane.

Indirect manipulation device

A device like a mouse where the movement occurs on a different plane (e.g., desktop) than the screen cursor, requiring hand-eye coordination.

Touchpad

Small touch-sensitive tablets used in laptops where a fast 'stroke' moves many pixels for initial movement and a slow 'stroke' moves fewer pixels for accurate positioning.

Trackball

An indirect pointing device where a ball is rotated inside a static housing; it is described as being like an upside-down mouse.

Touch-sensitive screen

A direct pointing device that detects a finger or stylus presence by interrupting light beams, capacitance changes, or ultrasonic reflections.

Eyegaze

A control interface that uses a very low power laser beam reflected off the retina to select menu items by looking at them.

Resolution

The number of pixels on a screen (e.g., SVGA $1024 \times 768$) or the density of pixels measured in dots per inch ($\text{dpi}$).

Jaggies

Discontinuities in diagonal lines caused by the horizontal raster scan process on bitmap displays.

Anti-aliasing

A technique used to soften the edges of "jaggies" and text by using shades of the line color.

Cathode ray tube (CRT)

An older display technology using an electron gun and magnetic fields to hit a phosphor-coated screen, associated with health hazards like X-rays and electromagnetic fields.

Liquid crystal displays (LCD)

Displays that work by applying voltage to crystals to change polarization and reflected light; they are smaller, lighter, and emit no radiation.

Digital paper

Thin flexible sheets updated electronically that retain their display using small spheres or channels with colored liquid.

Haptic devices

Interaction devices that provide touch, texture, and feeling, such as force feedback in simulations or vibration in games.

Laser printer

A printer that deposits dots of electrostatic charge on a drum to pick up toner, which is then fixed to paper with heat; typically $600\,\text{dpi}$ or better.

Serif

Fonts with splayed ends on characters (e.g., Times Roman) that help the eye follow long lines of printed text.

WYSIWYG

Acronym for "what you see is what you get," describing the aim of making the screen image match the printed output.

Optical character recognition (OCR)

The process of converting a scanned bitmap image of text back into digital character codes.

RAM (Random Access Memory)

Short-term, volatile memory on silicon chips with around $100\,\text{nano-second}$ access time and $100\,\text{Mbytes/sec}$ transfer rates.

Virtual memory

A system that stores some programs temporarily on disk to make RAM appear larger, though it slows the system down through "swapping."

Moore’s law

The observation by Gordon Moore that processor speed doubles every $18\,\text{months}$ and memory capacity doubles every $12\,\text{months}$.

TCP (Transmission Control Protocol)

A lower-level Internet protocol that manages packets of data sent between machines.

IP (Internet Protocol)

The protocol that establishes a reliable channel between programs running on different machines over the Internet.