Science -- Your Future, Scotland's Future
SCI-FUN Roadshow Exhibits -- Seven Segment Display
SCI-FUN Roadshow Exhibits -- Seven Segment Display
In this exhibit you learn about one of the methods that we use to represent numbers and letters on screens.

We use number and letter displays everywhere to show information. There are many different ways to display information, and technologies are improving all the time.

Seven segment displays (like the one in the title) were invented in the early 20th Century, but did not enter widespread use until the 1970s. They can easily display the numbers 0-9, but they cannot display all the letters, as they have no diagonal lines and are a fixed width.

For this reason, seven segment displays are mostly only used when only numbers are needed, such as for calculators, digital clocks or showing currency exchange rates. Some words can be spelled out using seven segment displays. Luckily for DVD player manufacturers, many of the words needed on a DVD player (such as no dISC, PLAy and PAUSE) can be spelled out, so seven segment displays are used for this purpose too.

Because of the difficulty of writing letters with seven segment displays, other methods are used to display writing. Dot matrix displays, with squares of 7 x 7 (or more) dots, can be used to display all the letters in our alphabet. These are often used to display information such as bus destinations and train times. For many years, this was better than displaying on a computer or television screen, as bright sunlight can cause glare making screens impossible to read.

However, flat-screen technology is getting better and cheaper. Displaying information on a computer screen allows greater flexibility: you can display anything, including pictures, writing or tables in whatever colour or style you like, and it is easy to change. With improvements in anti-reflective coatings for screens, glare is no longer a problem.

1 We use number and letter displays to show _________.
2 When were seven segment displays invented?
3 For what purpose are seven segment displays mostly used?
4 What problem did we used to have with computer or television screens?
5 What kind of things can be displayed on a computer screen?
6 Before the Internet, do you know how people used to look up news headlines, weather forecasts and other information at home?

1 Have a look at some old mobile phones and compare them to modern ones (ask your parents if they have kept any, or look at pictures on the Internet). How do the displays on old phones differ from new ones? Can you see how technology has improved?
2 Try to design your own number and letter display. You need a number of shapes that can be coloured in to make the different numbers and letters. What is the smallest number of shapes you can use to make all the numbers and letters?