Human input output channels and human memory

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Human Computer Interface:

Human Computer Interface Prof.A.Dennis Ananth AVCOE,Sangamner /


Agenda HCI -definition & basic concepts Input-Output Channels Human Memory

What is HCI?:

What is HCI? Study, planning ,design of the interaction between people and computers. Otherwise known as MMI or CHI On machine side, CG, OS, PL and development environments are relevant. On human side,comm.theory,linguistics,social sciences,cognitive psychology & human factors are relevant Eg:Poor Design lead to Three Mile Island Accident.

What is an Interface? :

What is an Interface? A point where two objects meet. A point where the human can tell the computer what to do. A point where the computer displays the requested information.

What Tools are Used?:

What Tools are Used? A keyboard, for typing, A mouse, for clicking, A scanner, for copying, A camera, for images. A monitor, for displaying, A printer, for printing, A sound card. For audio, A DVD, for video.

Human-Computer Interface:

Human-Computer Interface A human and a computer communicates. A human usually has 5 senses: Sight, Hearing, Touch, Taste, Smell, A computer hasn’t any senses as such, it is machinery, with electrons running around in and out of component devices.



Computer Match:

Computer Match A good interface match would include as many senses as possible. Computer input and output is basically seeing what we enter and what is displayed. Sound can be added to some programs, either by giving instructions by voice, or listening to a commentary / music. Touch can be in the form of using the mouse, a joystick, or a drawing tablet.

Graphical User Interface (GUI):

Graphical User Interface (GUI) Used on computers first by Apple Macintosh, and afterwards by Microsoft. The memory and file management are done by the operating system while applications are running – Multi-Tasking. A mouse is used to point and click on icons instead of typing in a command. Dialogue boxes, menus, icons, toolbars etc form the window on the computer screen.



Main Features:

Main Features Mouse: main input device, it moves the cursor across the screen. Left click for selection, Right click for a shortcut drop-down menu. Windows: many can be opened at the same time allowing for simple transfer of data between them. Toolbar Menus: that drop-down when clicked. Pointers: a pen may be used to point and draw using a graphics tablet.

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Standardisation The GUI is very similar in different applications. In an integrated package it will be almost identical from application to application. Word Power Point Excel

Common Features:

Common Features Users get used to an operating system. Commands are similar, keys and click perform the same tasks. Learning is achieved faster throughout different applications. Consistency in screen layout; menus, dialogue boxes, and error messages. Customisation is similar in applications. On-line help is offered in a similar way. In business users are much more efficient in their work if using common facilities.


Control The GUI controls the hardware, i.e. the use of memory, storage, printers. It can influence how the user interacts with the program they are working on. Being able to Open, Save, Print, and use Help in a word processor means the user can do it in a spreadsheet, a database etc without any further training. This makes it much easier to transfer skills from one application to another.

Menus (Whole Screen):

Menus (Whole Screen)

Menus (Pop Up):

Menus (Pop Up)

Menus (Pop Up [mouse right click]):

Menus (Pop Up [mouse right click] )

Menus (Pull Down):

Menus (Pull Down)

Disabled Users:

Disabled Users There are many featured designed for disabled users. A visually impaired person may be unable to use the GUI features, and find that typing in commands are easier. The printed output may be produced on Braille. A hearing impaired person may be able to use speech commands and listen to the output through speakers. This may also be a preferred method for users with other disabilities who cannot use a keyboard and mouse.


Forms A type of user interface (dialogue box), for entering or viewing data. Features: text boxes, labels, and buttons.

Command Driven Interfaces:

Command Driven Interfaces Had to type in a command. The syntax had to be correct. Difficult for inexperienced users. Example above: Microsoft DOS, and UNIX. Advantages: Powerful, Quick, and Flexible. Disadvantages: Difficult, need experience, Syntax difficult to remember, typing mistakes!

Natural Language:

Natural Language Normal speech recognised by a computer is Natural Language Interface. Talk to a computer and it recognises what we want. Natural means human-like, and the technology is leaning towards getting computers to behave in a more natural way.

Pointer Based:

Pointer Based Using a pen like stylus on a special pad or tablet. Used in freehand graphics, and CAD using special software that recognises the shape and style of the lines. Could also be a touch sensitive screen. All are easy to use and more natural than using a mouse.

Other Interface Devices:

Other Interface Devices Mouse. Keyboard. Touch sensitive pad. Speech recognition.

Human Input-Output Channels:

Human Input-Output Channels Vision Hearing Touch Movement


Vision The Human Eye Visual Perception Perceiving size and depth Perceiving brightness Perceiving Color Reading


Eye Cornea and lens at the front of the eye focus the light into a sharp image on the back of the eye,the retina. The retina is light sensitive and contains 2 types of photoreceptor Rods-highly sensitive to light Cones-Less sensitive to light

Perceiving size and depth:

Perceiving size and depth Objects of the same size at different distances have different visual angles. Objects of different sizes and different distances have same visual angle Visual acuity is the ability of a person to perceive fine detail.

Perceiving brightness:

Perceiving brightness Brightness is a subjective reaction to levels of light. It is affected by luminance which is the amount of light emitted by an object. As luminance increases,flicker also increases.

Perceiving Color:

Perceiving Color Color is made up of 3 components: Hue, Intensity,Saturation Hue -spectral wavelength of light Intensity -brightness of the color Saturation -Amount of whiteness in the color


Reading During reading, eyes make jerky movements called saccades. The eye moves backwards over the text as well as forwards,in what are known as regressions. If the text is complex,there will be more regressions. Adults read 250 words a minute.


Examples Muller-lyer Illusion-Which is Longer?

Ponzo illusion:

Ponzo illusion

Is this text correct?:

Is this text correct? The quick brown fox jumps over the the lazy dog.


Hearing The Human Ear-Outer ,inner & middle Processing Sound-Frequencies from about 20Hz to 15KHz. The auditory system performs some filtering of the sounds received allowing us to ignore noise and concentrate on important information.


Touch Haptic Perception 3 types of Sensory receptors Thermoreceptors -respond to heat and cold Nociceptors -respond to intense pressure,heat and pain Mechanoreceptors -respond to pressure.


Movement Movement time=a+blog 2 (distance/size+1) where a and b are empirically determined constants. Eg:hitting a button in response to a question involves a number of processing stages. Movement time -Phy.characteristic of the subject Reaction time -varies according to the channel through which stimulus is received.

Human Memory:

Human Memory Sensory Memory Short term memory Long term memory Sensory Memories Iconic Echoic Haptic Short term or Working Memory Long term memory Attention Rehearsal

Sensory Memory:

Sensory Memory Acts as buffer for stimuli received through the senses. Iconic Memory-Visual Stimuli Echoic Memory-Aural Stimuli Haptic Memory-Touch

Short Term Memory:

Short Term Memory Acts as a Scratch Pad for temporary recall of information Short term memory can be accessed in the order of 70ms. Two basic methods for measuring memory capacity Determining length of a sequence Items to be freely recalled in any order

Model of Short term memory:

Model of Short term memory Articulatory Loop Central Executive Visuo -Spatial Scratch Pad Auditory Imaging System


Examples Look at the sequence 265397620853 Now look at this sequence 44 113 245 8920

Long Term Memory:

Long Term Memory We store factual info, experiential knowledge, procedural rules of behavior. Two types of memory Episodic memory -represents our memory of events and experiences in a serial form Semantic memory -structured record of facts,concepts and skills that we have acquired.

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