10 Principles of a Good User Interface

by Joseph P Ferrari
Reprinted without permission
from STart Magazine Volume 4 No 1 (August 1989)

1. Be Consistent
Since a particular program will be only one of many that a consumer will use, the user interface should reflect the prevailing standards. Most software programs have operations common to each other – for example cut, copy and paste. When these options are always placed under the same drop down menu, for example EDIT the user can achieve productivity quickly without first struggling to learn the fundamentals.

Adhering to a common standard also helps to avoid user frustration. Assume for example that Control+X is commonly used for cut-and-paste functions; if a new program uses Control+X to exit without saving work, it will cause the user unnecessary hardship and frustration. If a user encounters enough of these frustrations he or she will eventually turn to an alternative.

2. Reduce the Workload

Operations should be achieved with a minimum of user activity. Too much “mousing around” means less time spent doing real work. For example, features that require a stream of menu operations and parameter settings to perform a single operation are clumsy.

You can reduce the user’s workload by building intelligence into the application. For example, in a work processing program, the spell checking function should not require the user to enter the dictionary path each time it is used. The program should have been set up intelligently so that each time the spell checker is used, the program doesn’t request the same information.

3. Reduce the Skill Required

Making your program accessible to the largest number of users is inextricably linked to the degree of skill a user needs to operate ot productively. The first are to consider is the user’s learning process. In many cases. the user faces multiple problems when learning to use a new application.

The user must come to terms with how the program’s functions are represented in computer actions. For example, many of the basic functions in a paint program are represented as a palette of icons representing graphic tools; in the user’s mind, the toolbox metaphor reinforces the idea that in order to apply a function , it must first be selected.

The user may be unfamiliar with the application in any form, computerized or conventional., and thus faces the task of understanding it’s concepts while at the same time using the software to perform some specific function. In the learning stages, the use of common metaphors for operations, such as the file drawer or open trash can icon on the desktop, can provide considerable reinforcement and help the user achieve a deeper understanding of the application.

One of the most important and effective means of reducing the skill required is to provide the user with visual choices. Let the user select from a panel of options by pointing and clicking and eliminate the need to memorize the available options.

4. Communicate

Keeping the user informed at all times is a vital component of sustaining or increasing productivity. There are three simple rules that should be followed :

(A) During long operations, provide continuous or regular progress reports. However, the time when you need to communicate the most information wit the greatest accuracy is during operations that have gone wrong. When an error occurs, you want to help the user recover from that error and restore normal operations.

(B) Present the available options in a clear and concise manner, leave no room for ambiguity. A an example, the user has selected the Quit option and the following alert message is displayed:

Do you want to quit ?
Continue ! Abandon

Does “Continue” mean to continue with the application or continue with the quit proceedings ? What about “Abandon” ? Leave no room for interpretation. Keep messages simple and explicit.

(C) Provide immediate feedback, both by acknowledging the users actions (in the case of selecting an icon, the standard feature is to hilight the icon) and by letting the user know whether or not the operation can be started.

5 Make What you see what you get

In a what-you-see-is-what-you-get (WYSIWYG) environment the user always has a good estimation of the final form of the document and doesn’t need to constantly invoke a preview mode. A WYSIWYG environment usually shields the user from unnecessary information. If text is in bold, it should show on the screen in bold rather than display a scheme of codes.

6. Allow for User-Configurable Preferences
Since a program or environment must cope with varying degrees of user proficiency, the product must accommodate the novice as well as the expert and be able to mold various program characteristics to the users preferences or level of expertise.

7. Provide a Stable Environment

Providing a stable environment will keep the user in a familiar atmosphere that makes learning easier. This does not mean that a dynamic menu bar cannot be employed successfully, such as in a multi-application environment where there are clear distinctions between aspects of the program, as in an integrated word processor, spreadsheet or database program. The changes would then assist the user by alerting him or her that the program is entering one of the other fundamental modes.

Graying out the unavailable options in drop-down menus or dialog boxes is also effective for maintaining a stable environment while limiting options.

8. Forgive the users Errors
An extensive undo function adds significantly to the users confidence to experiment and make changes. If the user does something that can’t be un-dine, an alert message should warn the user that the changes are irreversible.

9. Provide Keyboard Equivalents
Drop down menus are an excellent means of introducing the user to an application, but eventually the user will become proficient in specific areas of the program. At this point keyboard equivalents help the users productivity rise even more. Keyboard equivalents can also be used as shortcuts to commands that normally would require several menu selections.

10 Maintain Aesthetic Integrity
Screen layout design should not be designed to dazzle or impress the user. The guiding motive should be honest to the principle of effective communications. Simplicity is the key to clarity.

Another principle to observe is to avoid overloading the user with too much data in a screen layout. You don’t want to fill every pixel on the screen. If the pertinent data cannot fit comfortably in one screen panel the divide it logically and use as many screens as required.

One main reason that the Macintosh has become a second standard in corporate America is its user interface – and the fact that most of the software developers have adopted the interface to a significant extent. ST software developers will need to do the same to increase it’s future chances.

Joseph Ferrari was the director of Software Development for Atari Canada. After that he directed software development for Atari Corp. US, where his efforts were focused on developing the Mega/Laser printer combination as a desktop publishing workstation. He is now back in Toronto where his new company, Personal Productions Ltd, develops interactive multimedia productions. Joseph says that because the general public tends to be intimidated by computers, user interface design is the number one priority for acceptance in the multimedia market.

Sit on it

Where do you sit ?

(the following observations based on attending too many lectures)

Ever wonder why a lecture room, auditorium or any place of gathering only seats a small proportion of the total allocated ?

This is because of the different types of people that inhabit such environments. First you have the quick thinking and smart (OK, anyone like me) individual. These turn up on time and head straight for the middle of the row, they wait and observe the other participants arriving.

Next comes the slower ones. They will need to choose a row and enter from one end, carefully deciding how close to sit to the clever buggers who got there first.

Some will rush up and take a seat next to those already sitting. If they are mildly annoying they will say hello and then stare vacantly ahead for the remaining time until the event commences. If they want to be really annoying they will inquire about the weather, why others are present and may even expose their uninformed views on the subject matter for the evening. They may chatter until the commencement of proceedings. Such people are rarely invited back.

Now here come some more, but this time they may not like those already seated. They will choose a seat some distance from those seated, perhaps four to five away. And for extra protection a bag (or whatever they have) will be placed between them and the idiot further along the row. But they have to be careful not to sit too far to the end, as they may encounter the worst individuals of all.

The most common spacing will be with one seat between people. This is throwback to childhood when schoolchildren were instructed to stand at least one arms length apart. A measurement of the distances between people will confirm that some practices persist into adulthood.

Now the worst of all, the person who sits at the end of the row. This obnoxious individual is obviously unaware of problems they cause to others. Everyone else has to squeeze pass them to get to a seat somewhere in the middle. If you are trying to pass, be sure to carry a bag or case and gently smack them in the face as you pass.

Now everyone has arrived and seating is complete. But here comes the speaker/lecturer. Some of these may attempt to break the seating formation. “OK, everyone. Don’t sit at the back. Come on down, there are plenty of seats at the front. Come on now, I won’t bite. I just want us to all get cosy today”. Under no circumstances should you move. People have already spent good time and effort in acquiring their seats. They are not going to move. So just cross your arms, lean back in your chair and give them a look of “Buggered if I’m going to move”. Eventually any efforts to get you to move will be unsuccessful. You can stay where you are.

So now we have it, a few in the middle, the idiots on the end some more scattered in the remaining seats. This formation can be seen in as a graphical representation of the bell shaped curve of intelligence. The intelligent ones in the middle, with those of lesser intelligence on the extremity of each row. And everyone wondering “Why did I come here ?”.

So, Where Do You Sit ?

NB 28/11/2003


Written by William Shakespeare
Directed by Ross Gumbley
Featuring Mark Hadlow and Lara Macgregor

Shakespeare’s darkest and most powerful tragedy tells the story of Macbeth, the brave general who, returning victorious from battle, witnesses a prophecy from three witches that he will one day become King.

Driven by his ambitious wife, Lady Macbeth, the idea of being king grows into an all-consuming desire for power. After murdering the King, Macbeth takes the throne, dispatching all that get in his way. But the witches have another prophecy, one that will end Macbeth’s treacherous rise to power, one that will play out to its bitter and bloody end.

A sharp warning of the infectious and corrosive lure of power, Shakespeare’s Macbeth still reigns supreme after 400 years. To see it onstage is to see our own society played out before us, set in a world we can all relate to.

This suffers from the same thing all the Shakespeare I have seen. Due to the actors slavishly adhering to the old style prose and delivery, it’s often difficult to determine what’s going on. In fact halfway through the first act it all rumbled over me and became boring. By the time I got used to the language in the second half, it was drawing to a rather predictable close. It’s the ‘John Carter’ film problem. All the themes seem old and derivative because they are seen so often. But this is actually the origin of a lot of the plots we see in modern storytelling. (2/5)




Gravity Waves

UC Connect: Black holes making waves around the Universe

Professor David Wiltshire, Department of Physics and Astronomy
Monday, March 7, 2016 from 7:30 PM – 8:45 PM
C1 Lecture Theatre, University of Canterbury

On 14 September 2015 the two LIGO detectors measured gravitational waves for the first time ever, produced by the collision of two black holes 1.3 billion light years away. This opens a new era of astronomy, a window on things we cannot observe by other means. It vindicates Einstein’s 100 year old prediction of gravitational waves, and the rotating black hole solution of Einstein’s equations discovered in 1963 by New Zealander Roy Kerr.

In measuring distance changes a thousandth the size of a proton, this is also the most sensitive measurement ever achieved by humankind. It represents the culmination of four decades of work by thousands of experimental physicists, engineers, mathematicians, numerical modellers and astronomers, who together have had to overcome challenges in fields as diverse as seismology and fundamental quantum optics. Last December, the LISA pathfinder satellite was launched, the first step in taking gravitational wave detection to space. This lecture will reflect on what has been achieved, the technological spin-offs and challenges ahead, and what we might discover in the new age of astronomy ahead.

Notes from wikipedia:
Gravitational waves are presently understood to be described by Albert Einstein’s theory of general relativity. In the simplest cases, and certain less-dynamic situations, the energy implications of gravitational waves can be deduced from other conservation laws such as those governing conservation of energy or conservation of momentum.

On 11 February 2016, the LIGO collaboration announced the detection of gravitational waves, from a signal of two black holes with masses of 29 and 36 solar masses merging together about 1.3 billion light years away.

During the final fraction of a second of the merge, it released more power than 50 times that of all the stars in the observable universe combined. The signal increases in frequency from 35 to 250 Hz as it rises in strength. The mass of the new black hole obtained from merging the two was 62 solar masses. Energy equivalent to three solar masses (our sun is 1 solar mass, 2×10^30 Kg) was emitted as gravitational waves in about 1/10 of a second. The signal was seen by both LIGO detectors, in Livingston and Hanford, with a time difference of 7 milliseconds due to the angle between the two detectors and the source. The signal came from the Southern Celestial Hemisphere, in the rough direction of (but much further away than) the Magellanic Clouds. The confidence level of this being an observation of gravitational waves was 99.99994%.

Amplitude: Usually denoted h, this is the size of the wave — the fraction of stretching or squeezing in the animation.
Gravitational waves passing through the Earth are about 10^−20m.

Wave amplitudes from the Earth–Sun system
We can also think in terms of the amplitude of the wave from a system in circular orbits.
Suppose that an observer is outside the system at a distance 0.08 Light Years (7.5 x 10^14m) from its center of mass. Typical amplitudes will be h ≈ 10^−25m. This is well under the detectability limit of all conceivable detectors.

Power radiated by orbiting bodies
Two stars of dissimilar mass are in circular orbits. Each revolves about their common center of mass (denoted by the small red cross) in a circle with the larger mass having the smaller orbit.
Two stars of similar mass are in circular orbits about their center of mass

Gravitational waves carry energy away from their sources and, in the case of orbiting bodies, this is associated with an inspiral or decrease in orbit.  Imagine for example a simple system of two masses — such as the Earth–Sun system — moving slowly compared to the speed of light in circular orbits. Assume that these two masses orbit each other in a circular orbit in the x–y plane. To a good approximation, the masses follow simple Keplerian orbits. However, such an orbit represents a changing quadrupole moment. That is, the system will give off gravitational waves.

In theory, the loss of energy through gravitational radiation could eventually drop the Earth into the Sun. However, the total energy of the Earth orbiting the Sun (kinetic energy + gravitational potential energy) is about 1.14×10^36 joules of which only 200 joules per second is lost through gravitational radiation, leading to a decay in the orbit by about 1×10^−15 meters per day or roughly the diameter of a proton. At this rate, it would take the Earth approximately 1×10^13 times more than the current age of the Universe to spiral onto the Sun.

In Fiction: An episode of the Russian science-fiction novel Space Apprentice by Arkady and Boris Strugatsky shows the experiment monitoring the propagation of gravitational waves at the expense of annihilating a chunk of 15 Eunomia the size of Everest. The novel was written in 1961 and published in 1962, exactly at the time when Soviet physicists Michail Gerstenstein and Vladislav Pustovoit prepared and published their proposal on using laser interferometry for gravitational wave detection.


2004 Film Reviews

Film Reviews from Film Appreciation Course Feb/Mar 2004

As a result of these classes I have moved from being un-informed and ignorant to informed and stupid. So here it is…..
For my records and your reading, a quick review of the films viewed and, as is the convention, a rating for each.

Nobody’s Business
Before seeing this film, I always regarded the documentary style as being more suited to TV. However this film prompted me to see “The Fog of War”. This film only succeeds due to Alan Berliner’s mix of cinematic styles, all gel to form a compelling narrative of his cranky father. An enjoyable movie with a old man in a starring role you are not likely to forget quickly.

Rating 7/10

The Man with a Movie Camera
This was a surprise for me. I didn’t believe that any film from 1929 could be so inventive and “modern”. Even now it has relevance in a western post-industrial society. It just shows how little most of our lives have changed. It’s just a great kaleidoscope of shapes and movement.

But most of all, I liked the music. The film shown had a soundtrack by “The Alloy Orchestra”, I have since found another by “The Cinematic Orchestra” which I own. And recently found another by the group “Biosphere”, it’s the second disk on their “Substrata V.2” album. This one is described as ambient and all I can find is a reference at www.amazon.com to the CD.

Rating 9/10

I had never heard of this film before seeing it. It’s mix of day-glow colours and computer animations form a wonderful stylistic whole.

One scene that remains in my memory is when Amelie is skimming stones. The camera starts behind her, arcs over and after almost 180 degrees ends in front of her. The camera movement is similar to Peter Jackson’s films, both often have the viewpoint up high, with the camera sweeping down to the subject in detail.

Best of all is it’s witty and often dark humour. I didn’t think I would enjoy a film where I had to _read_ all the dialogue. This one goes on my list of “Best Films Ever”. Perfectly formed.

Rating 10/10

Heavenly Creatures
I had seen this film when it was first released and later when it was screened on TV. This is the film where you can see Peter Jackson for the first time as a world class director. He manages to keep the pace of the film going at the right speed, varying where necessary and reaching a slow build-up of tension towards the end. This despite knowing what the end will be from the very beginning.

His mastery of the medium displayed in this film I’m sure is what gave New Line the confidence to spend 200-300 million and 8 years on the biggest film trilogy of all time.

It would be a mistake to make direct comparisons to the other Jackson films. I have read a biography of Peter Jackson and it is clear that his partner Fran Walsh was a big influence in Peter making this film and in it’s execution. I think this is better than his later film “The Frighteners”.

Rating 10/10
(Jacksons second best film to LoTR)

400 Blows
Grey, bleak, dull and boring sum up this movie for me. I can’t believe this could be enjoyed by anyone except for the directors friends and family (including his parents).

This film starts off slowly and gradually progresses to something even slower and duller. I was not impressed, I couldn’t even keep awake and missed 10-20 minutes near the end due to falling asleep. Did anything happen ?

Rating 0/10 (recommended for insomniacs)

Dancer in the Dark
I’m sure that one of the first things they teach in film school is…… hold the camera steady to get a good shot. Avoid sudden movements, quick panning and excessive zooming. In the first five minutes of this film, all the above “rules” were broken. There is a photo in the biography of Peter Jackson, it shows him with a custom made rig to hold the camera steady. Peter went to a lot of trouble to get a steady camera, something Lars von Trier hasn’t bothered with in this film. At first I thought it was some sort of cheap introduction, I can understand using a hand-held camera to enhance movement and intensity. Jackson does this at the end of “Heavenly Creatures” and it works. In this film it doesn’t, if this is “experimental” then the experiment failed. If it’s part of the “style” then it completely undermines the telling of the story. And what is worse is that after 20 minutes I was starting to get a headache.

I actually like Bjork’s music (I have most of her albums), but as an actor she is not very engaging. There were no characters I could relate to and story of minimal interest. I liked the musical numbers (here the cameras were nailed down !) as they added a lightness and diversion to an otherwise below average movie.

I hope that next time, the director employs a better camera operator.

Rating 0/10 (for the headache)

I saw Casablanca for the first time on TV several years ago. So I was a bit surprised to find the film in black and white. I presume this is one of the films given a dash of colour at a later date. When I first saw the film, I thought it was about a “femme fatale” who manipulates men to her own advantage. Seeing the film again my opinion is unchanged.

Ingrid Bergman is, as usual, stunningly beautiful and succeeds in her escape mission; have you ever seen a beautiful woman ask a favour of a man and not get one ?
She does manage to string two seemingly intelligent men along for most of the film, putting on the charm when necessary.

I may also be that I just can’t relate to Bogart as the “Hero”. He doesn’t look or act like one, he looks more suited to a Hollywood gangster movie (and as the bad guy). The best character was the French policeman.

There is no doubt that the film succeeds in atmospherics and style.

I do find it amusing that critics think the film makes a lot of references to other cultural references like Huck Finn, Washington etc and see it as propaganda. I think the general public would not see anything beyond the story. Or perhaps it’s just that I am not American.

Still, a good story and enjoyable. Even if it just perpetuates the myth that the Pretty Women always get what they want.

Rating 6/10

Goldiggers of 1935
The musical numbers have a great style and panache, mixing conventional and experimental film making techniques. The remaining story was a bit of a cliche of goof-ball comedies of the period. It did have wit and a dry humour that kept the story going. But ultimately it’s the musical numbers (especially those pianos) that remain as memories of the film.

Rating 6/10

Citizen Kane
I can see why this film is appreciated by those in the film industry. It sets a lot of standards for others to follow. I don’t know what all the fuss is about “Rosebud”, it’s clear to me that the sled represents the memories of Kane as a child, of a simpler and innocent time he is trying to recapture.

A good and intriguing film that keeps you interested until the end (and isn’t that what it’s all about?).

Rating 7/10

Bowling for Columbine
After a considerable amount of publicity, I saw this film in the theatre when it first came out.
Michael Moore is unashamedly the centrepiece of the movie. This is what gives all the interviews and stunts their cohesion and focuses the film. It would be a mistake to see this as Moore’s ego in flight. He has a self-depreciating sense of humour that may be more obvious in his TV show. I think Moore understands the medium as well (if not better) than his critics and deliberately puts himself forwards as Satan’s little helper, prodding and needling people into saying (and doing) things they would not do if he was located behind the camera.

Ultimately is success as a great social commentary on America, even it it reaches no conclusion.

Rating 8/10


So, overall I enjoyed the course; 8 out of 10 (better than usual) evenings I enjoyed. And there were only three films I had seen before.

Nigel Baker 13/4/2004


Why I don’t go skiing

Skiing isn’t a good idea. You need to be rich, flash and stupid. Let me explain.

First you will need to go shopping. Start with lots of money, you will be needing everything you can lay your hands on.

Now find a ski shop. These are only open in the winter. During the summer months they are usually used by some obscure charity organization selling hand crafted walnuts from Bolivia.

First you will need skis. These are 2m long planks. You may think they are for conveying you gently down a slope. This is not true. They are levers, inevitably your body will not be traveling in the same direction as the skis. Because high tech materials comprising wood and plastic are stronger then flesh and bone, injuries to sensitive parts are inevitable.

Expect injuries due to broken legs, sprained ankles and twisted knees to persist into old age. To protect your legs from protruding rocks, and wind blown snow you will need trousers.

These come in two styles :

The first is a skin tight, body hugging (show every curve) type. You should only consider purchasing these if someone (apart from spouse or family member) considers that you have sexy legs.

If you have sexy legs and breasts you should consider the full body suit. This body enhancing multicolored condom will ensure a quick response should you receive an injury.

The second style is the retro eighties styled baggy trousers. These tents will provide you with an accompanying wind song as you plunge over a cliff to your death. They will also provide men with camouflage should they have an involuntary response to the type one body suit.

You will need torso protection. Here the color is important. You will require something with sufficient color so you can hide in a tow queue. But not too bright or the keas will mistake you for a shiny object to either attack or take back to the nest as a plaything for the chicks.

Eye protection is a must. Again there are two choices.

The first is the dark glasses. These are available in a range of prices to match your social status. Expect to pay more for these than you did for your prescription glasses.

The second type is goggles. These can provide full face protection and camouflage. Especially useful when it’s your turn to clean up the mess at the end of the day.

You will also need pointed steel sticks, with a depth gauge in the end. This is used to prod others in the backside if they get in the way. The depth gauge is to ensure you don’t rupture any bowels. To make things even more dangerous, you will require two.

Now that you have spent several thousands, you have completed most of the spending. Soon you will be expected to spend only hundreds of dollars per day.

At about 11pm the night before your big day, expect your drunk friends to phone reminding you to be up early for the 7am start. They will inevitably arrive about 8am, after some of the company have forgotten to pack sufficient alcohol for the day.

If you are going to Mt Hutt be warned. When scaling the mountain the driver will remark at every bend “It’s about here that the strong winds will blow us over the side to the rocks below”.

If you are fat, expect to be asked to sit on the bonnet to provide traction for the final near vertical climb to the car park.

If you have been spending the first hour of your journey bragging about your gym work-out routine, be expected to push the car. If you have been comparing yourself to Hercules, be expected to lift the car while the chains are fitted.

It is a good idea to inquire of your friends if they have experience fitting chains to the correct wheels. If they hesitate only slightly, give them up for those who know what they are doing.

When you finally arrive you will require tow tickets. The queue should be about 50m long, but don’t worry, this is deliberate. You will need the practice at waiting when you get to the tow queue.

Now for the fun part of your day, getting up that white hunk of rock. The gray things on the snow are not fallen, fashion free skiers. They are rocks. You have arrived either early in the season before the snow maker has been repaired, or late when the snow is beginning to melt, and your family is spending their time at the beach. Remember that in New Zealand the ski fields are covered in tussock during summer.

Your method of getting to the top may vary. If your tow ticket was very cheap, expect to grab a hold of the farm tractor before it leaves.

A club ski field may have a rope tow. Don’t try grabbing the rope with your hand, that’s what a nutcracker is for (and don’t attempt to crack any nuts with it). After a day you will begin to develop upper body muscles. By the second day the pain should subside and you can start skiing properly.

The better ski field will have a “T” bar. This giant hook is for you. Just snuggle up closely to that geriatric old fart trying to reclaim his youth and wait.

When the hook hits you three thing can happen –
1. You could be taken safely to the top, but that is unlikely.
2. You could lurch forward, tangling your skis with your partner and falling in a heap in the path of the next pair of skiers.
3. Or you could sit down (a common error of the uninitiated). This will find you on your bum, sitting on your skis, sliding backwards into the tow queue. The sticks of those waiting should stop you. Just hope that they don’t use them in a horizontal manner, with the depth gauges removed.

Once you have mastered the art of rising gently to the top of the hill and tumbling down again you can call yourself a skier. By about 2pm you will get bored with all this and join your friends in the public bar. Don’t worry about your driver not drinking, this is a kiwi custom. Anyway it’s all downhill to home, you will make it home eventually.

When you finally get home (the same day unless you have stopped at a hotel on the way) you can relax.

Now reflect that it would have been better to stay in bed on a winters day and read.

And that’s why I don’t go skiing (anymore).

Nigel Baker


Ergonomics – The Human Factor

By Jim Oren

(This Article was excerpted from the Antic Online’s Professional GEM Column)
Reprinted without permission from STart Magazine Volume 4 No 1 (August 1989)

A reader of a novel or science fiction story must suspend disbelief to participate in the story. If the author’s grammar or plot it clumsy, it jars the reader and breaks down the illusion., pulling the reader out of the story. Similarity, a software designer who fails to pay attention to the speed and consistency of a program’s interface will distract users from the programs functions and detract from the care that has been lavished on the function of the program.

Making an interface fast and useable is often treated as a black art.. It isn’t – there are well known methods derived from the field of ergonomics, the study of interaction between man and machine. The ergonomics of the human computer interface were studied extensively at Xerox PARC, the birthplace of the Alto, Star and smalltalk systems which led to the Macintosh and the Atari ST. The designers of these original systems knew and applied the principles of ergonomics.

What follows is a short venture into the world of ergonomics. You will find more than the usual quota of math, slated with examples of real design problems. But there is no way print can convey the vibrancy and tactile pleasure of a good interface, or the sullen boredom of a bad one.. The best way to make ergonomics real is to look for your own examples . Get out your favorite arcade game and see if you can spot some of these principles in action. Dig out the most annoying program in your reject pile and look for the mistakes. Then look at your own with a critical eye.


We’ll start right at the users fingers with the basic equation governing the positioning of the mouse, Fitt’s Law:

T = I x LOG2(D/S + 0.5)

T is the amount of time to move to a target
D is the distance of the target from the current position.
S is the size of the target, stated in equivalent units.
LOG2 is the base 2 (binary) logarithm function
I is a proportional constant, about 100 milliseconds per bit, which corresponds to the human’s “clock rate” for making incremental movements.

We can squeeze an amazing amount of information out of this formula when attempting to speed up an interface. Since motion time goes up with distance, we should arrange the screen with the usual working area near the center, so the mouse will have to move a smaller distance on average from a selected object to a menu or panel. Likewise, any items which are usually used together should be placed together. The most common operations will have the greater impact on speed, so they should be closest to the working area and perhaps larger than other icons or menu entries. If you want to have all operations take about the same time, then the targets furthest from the working area should be larger, and those closer may be proportionately smaller.

Consider the implications for dialogs. Small check boxes are out. Large buttons which are easy to hit are in. There should be ample space between selectable items to allow for positioning errors. Dangerous options should be widely separated from common selections.


If you used the ST desktop for any period of time you’ve probably noticed that your fingers know where to find the file menu. This phenomenon is sometimes called “muscle memory” and its rate of onset is given by the Power Law of Practice:

T(n) = Y(1) x n-a

T(n) is the time on the nth trial
T(1) is the time in the first trial, and is approximately 0.4.

The first thing to note about the power law is that it only works if a target stays in the same place. This should be a potent argument against rearranging icons , menus , or dialogs without some explicit request by the user. The time to hit a target which moves around arbitrarily will always be T(1).


Just as fingers are the way the user sends data to the computer so the eyes are the channel from the machine. The rate at which information may be passed to the user is determined by the “cycle time” of the user’s visual processor. Experimental results show that this time ranges between 50 and 200 milliseconds.

Events separated by 50 milliseconds or less are always perceived as a single event. Those separated by more than 200 milliseconds are always seen as separate.

Suppose that your application ‘s interface contains an icon which should be inverted when the mouse passes over it. We know that flipping it within 1/20th of a second is necessary and sufficient. Therefore if a “first cut” at the program achieves this performance, there is no need for further optimization, unless you want to interleave with other operations.

If it falls short, it will be necessary to do some assembly coding to achieve a smooth feel.

On the other hand, two actions which you want to appear distinct or convey two different pieces of information must be separated by an absolute minimum of a fifth of a second, even assuming that they occur in an identical location on which the users attention is already focused.

It should be quickly added that stimulus enhancement will only work when it unambiguously draws attention to the target. Three or four blinking objects scattered around the screen are confusing, and worse than no enhancement at all.

Short Term Memory

Both the information gathered by he eyes and movement commands on their way to the hand pass through short term memory (also called working memory). The amount of information that can be held in short term memory at any one time is limited. You can demonstrate this limit on yourself by attempting to type a sheet of random numbers by looking back and forth from the numbers to the screen. If you see like most people, you will be able to remember between five and nine numbers at a time. So universal is this finding that it is sometimes called “the magic number seven, plus or minus two”.

he shirt-term capacity sets a limit on the number of choices which the user can be expected to grasp at once. It suggests that the number of independent choices in a menu should be around seven, and never exceed nine. If this limit is exceeded then the user will have to take several glances, with pauses to think in order to make a choice.


The effective capacity of short term memory can be increased when several related items are mentally grouped as a “chunk”. A well designed interface should promote the use of chunking as a strategy by the user. One easy way is to gather together related options in a single place. This is one reason that like commands are grouped into a single menu which is hidden except for the title . If all the menu options were “in the open” the user would be overwhelmed with dozens of alternatives at once. Instead a “show info” command, for instance becomes two chunks: pick file menu, then pick show.

Sometimes the interface can accomplish the chunking for the user. Consider the difference between a slider bar in a GEM program and a three digit entry field in a text mode application. Obviously, the GEM user has fewer decisions to make in order to set the associated variable.


This article is a modest sampler from a much larger field. The Card, Moran and Newell book was the primary source for this article.

Stuart K Card, Thomas P Moran & Allen Newell :
The Psychology of Human-Computer Interaction
Lawrence Erlbaum Associates, Hillsdale, New Jersey 1983
(fundamental and indispensable. This volume of experimental results make it weighty. The good parts are at the beginning and end)

Macintosh User Interface Guidelines – Inside Macintosh
Apple Computer, Inc. 1984
(Though not everything translates this is a fine piece of principled design work)

James D Foley, Victor L Wallace and Peggy Chan
The Human Factors of Computer Graphics Interaction Techniques
IEEE Computer Graphics (CG&A) Nov 1984 pp 13-48
(A good overview, including higher level topics. Excellent bibliography)

J D Foley and A Van Dam
Fundamentals of interactive computer graphics.
Addison Wesley 1984, Chapters 5 and 6
(If you can’t get the article above, read this. If you are designing graphics applications, buy the whole book. Staggering bibliography)

Ben Shneiderman
Direct Manipulation : A step Beyond Programming Languages
IEEE Computer August 1983 pp57-69
(What do Pac-man and Visicalc have in common ? Shneiderman’s analysis is vital to creating hot interfaces.

Oren, Tim
Professional GEM
Antic Online, Compuserve
(The complete text of this article and several others on the same topic are included in Tim’s Professional GEM column in the index section of Antic Online. Log onto CumpuServe and type GO ANTIC)

Tim Oren was a member of the original GEM Team at Digital Research and designed the GEM resource Construction Set, later ported to the Atari ST. After leaving DRI he designed the GEM version of KnowledgeSet’s Graphic Knowledge Retrieval System, one of the first hypertext systems available for CD-ROM. At the same time he was the author of the Professional GEM series of online columns in Antic Online and contributor to the inaugural issues of Start. Tim is currently employed by Apple computer’s Advanced Technology Group, where he leads a project in multimedia information retrieval. (1989)


Lexx 3.07 & 3.08



Lexx 3.07 – Tunnels

Kai is brought before “The Commission”, who, in a room full of candles, endeavour to civilly interrogate him, exploring his human evil. Kai is not interested, and requests to be thrown off the tower. The adjudicatrix asks him whether he has killed anyone as an assassin. Kai then delivers his famous speech: “I have killed mothers and their babies. I have killed great philosophers and proud young warriors. I have killed the evil and the good, the intelligent, the weak and the beautiful, but it’s been a while since I slaughtered a whole room full of petty bureaucrats”. Meanwhile, Stan encounters an amateur surgeon, who feels that he has parts that “he’d feel better without”. Prince plays good guy, and dies saving Stan. He wanted Stan to love him. Xev plays with some girls who like bear traps.


Lexx 3.08 – The Key

Using an incarnation in Xev’s image, Prince continually probes Kai, 790, and Stan, asking for a way to get the key to the Lexx. They hook Stan up to 790’s diagnostics and Kai determines that the key could be released during sexual rapture, instead of the ecstasy near death which Prince is so familiar with. Prince then concerns herself with a complicated ritual to give Stan the ride of his life. Kai gets suspicious and tests the Xev impostor twice, to see if she kisses like a real Xev. After obtaining the key, she then countermands the order to destroy planet Fire, and directs Lexx to Water. Kai then kills her, and the key flows to a dismayed Stanley.

Lexx 3.05 & 3.06



Lexx 3.05 – Gondola (March 5, 2000)
In a dramatic survival episode, the crippled moth falls to Fire in the night. Duke and Fifi also crash. All of them have to make it to a city before the sun rises, or they’ll fry. The Lexx team: Bunny, Xev, Stan, and the two Kai’s find a wrecked gondola and pump it up. During their flight, they realise that there is not enough fuel to make it across the lava lakes, unless there is less weight. The protoblood Kai volunteers to jump overboard and walk through the lava on foot. Duke decides it’s easier to just to sit in the desert and die, which worries Fifi a bit. Duke explains the Water/Fire reincarnation system. However, the Lexx team find them, and stupidly pick them up, unable to solve the moral dilemma. Bunny gets thrown overboard. Stan and Xev make it to tower of K-Town, and then defend themselves against mortal-Kai

A simple survival story with a twist at the end. Just average (3/5)


Lexx 3.06 – K-Town (March 12, 2000)

On entering K-Town through a hole high in the wall, Xev and Stan have to deal with the tunnels and the demented inhabitants – the most evil of the souls incarnate. They meet some people who enjoy throwing rocks at them. Kai climbs up the tower, finds them, and then has a systems failure. They also meet Mantrid, who is devoid of memory, but highly encouraged by the idea that he is the greatest biovizier who ever lived. He participates in Kai’s diagnostic procedure, does something stupid, and then Kai cleanses him. Xev and Stan manage to throw Kai off the tower to realign him, but it doesn’t work, and he gets captured.

What a mess of story threads that don’t work and make no sense. The re-appearance of Mandrid is illogical and Kai’s ‘undergarment’ is unnecessary and probably belongs in a 1990’s puzzle adventure game. (1/5)


Lexx 3.03 & 3.04



Lexx 3.03 – Gametown

Stanley begins plotting how to destroy the planet Water without alerting Kai and Xev, or steering the starving Lexx. May gets better or worse, depending on his attitude. After waking the moth breeders, Kai goes to Gametown to find some food for Lexx. Gametown is a floating city inhabited with aerobics enthusiasts who play basketball all day. There is one inhabitant who is not quite right: Fifi. He doesn’t play the games by the rules, and he quickly betrays everyone, by stealing all the moths and food, then heading over to Fire, to surrender himself to Duke, so he can destroy Water. Stanley’s attempts on Water are foiled by Xev, who nearly strangles him, then smothers him with her breasts. May ridicules him, and heads off with Prince.

Some interesting plot turns, but undermined by slow pacing and lacking any tension or excitement. The weird thing is that on a mainly water planet, with no sign of land, the food offered is mainly fruits !!
Where is the fish and seafood ?


Lexx 3.04 – Boomtown

Duke and Fifi attack Gametown. They kill everyone he knows and raze the town. Duke likes Fifi. Kai requisitions an attacking moth, and then heads over to Boomtown with Bunny and Xev. All they do in Boomtown is eat and have sex. Stan is thrilled to find a number of the women willing to sleep with him, but Xev isn’t so lucky, as the men have adapted way of avoiding sex by interminable foreplay. Bunny makes several efforts to have sex with Kai, which he finally deterrents only by cutting of his left hand to demonstrate that he is not alive. Back on Fire, May kills Prince in a questionable gambit, then Duke and Fifi decide they’ll paint May and his former deputy with explosive tar, and burn them. Duke and Fifi fly to Boomtown and burn it.

The most frustrating thing about this episode is Xev, for a long time she has complained about lack of sex and showing she can be aggressive when it comes to Stan. But in a situation with a willing male, suddenly she becomes submissive. And the character of Fifi makes no sense at all. Where did he come from and why has he become psycho # 3. Kai’s unwillingness is indulge in sex is strange, given that all of his appendages appear to be working. At least Stan finally gets his way, but why is he wearing a nappy ? Very illogical episode (1/5)