What Is Datext?

Datext is a do-it-yourself system for creating and displaying pages of teletext-style information on the BBC Micro.

It consists of two programs: the Editor, a sort of toolkit, and Datext, the display program proper.

The Editor allows you to create and alter teletext pages and store them on tape for later use.

Datext is used to display the pages you've created with the Editor program. You can display the pages one at a time on request or you can have the micro display a series of pages one after the other in a continuous cycle.

The purpose of the system is to provide information in an attractive and dynamic manner. It can be used in exhibitions, schools, shop windows and wherever a lively, running display is needed.

Datext

Datext is the program that is used to produce the display on the BBC Micro's monitor or TV screen. When you load the program from tape and run it you will see a request for you to play the data tape. The first time you do this you probably won't have created a data tape. So after Datext, on the same tape, there are five teletext pages ready to be loaded and displayed. These summarise the instructions for using Datext and the Editor.

Once you've loaded these pages, a series of questions will appear on the screen. Your answers to these decide how the pages will be displayed.

The first question asks you to choose whether or not you want to be able to return to this set of questions should you change your mind as to how the display should work.

In the normal course of events, you can return to the questions by pressing the key marked CTRL and the X key at the same time. However, you can disable this feature if you want to prevent others from disrupting your display!

Once you've made this decision, another question appears asking you to select how the pages will actually be displayed.

If you want the pages to appear one after the other in an endless cycle, you pick automatic page selection. You'll then be asked to decide how long each page should be shown on the screen before the next one is displayed. Usually a time delay of 30 seconds is adequate.

Alternatively, you can choose 'select mode'. This enables you to pick a page by typing in its three-figure number. When you want to move on to another page, you just enter its number (which will appear on the top right of the screen as you type it in) and press the Return key.

The number of the page being displayed is shown at the top left of the screen. The range of available page numbers is shown in brackets in the centre of the top line.

The Editor

The Editor is the program that allows you to create and save your own pages and change them once you have them.

When you load and run it you will be given a list of five options. You can choose between 'edit' (creating or modifying pages), 'moving' them around in the display cycle, 'loading' pages from tape (usually to alter them), 'saving' the pages to tape and, finally, 'leaving' the program.

Choosing edit allows you to make up new pages or alter the ones you already have. You simply enter the number of the page you wish to work on. It doesn't matter if the page you choose is blank, you can write on it from the keyboard, easily and quickly.

You enter text from the keyboard in the normal manner, the Delete key being used to erase mistakes and the cursor keys to move around the screen.

By pressing the CTRL key and a capital letter key at the same time you can write to or alter the page. You can delete and insert lines and characters within lines.

In addition, teletext control codes can be entered from the keyboard to enable colour changes, to enlarge characters and to provide the familiar teletext graphics.

A full list of these keyboard control codes is given in Figure I. They are quite easy to use and it only takes a little practice before pages can be entered with ease.

The graphics characters can be entered at the keyboard using punctuation symbols and lower-case letters as shown in Figure II.

Text colour can be changed by pressing the CTRL key and the C key at the same time, then a number from 1 to 7 depending on the colour required. Figure III gives the colours that each number represents.

Colour graphics characters are selected in exactly the same way except that you press the CTRL and the G key at the same time, then the colour number. You can return to the menu by pressing CTRL and X.

The move page option allows you to change the position of pages within the sequence. Also, you can copy one page t another page number, useful if you want a page more than once in a sequence or if one page is very similar to anther and only needs a few alterations. You type in the number of the page you want, moving or copying and then the page number you want it to be moved or copied to.

As you might guess, the load option allows you to load pages that have previously been stored on tape.

Similarly the save option allows you to save pages on tape for later use. You can select how many pages you want to save, a facility that allows you to avoid saving any blank, wasted pages.

One point to remember is that when you are saving, say, page numbers 100 to 108, there are actually nine pages. Also owners of a BBC Micro with a 0.1 OS will need to have run the patch which allows them to save on cassette.

Finally, the exit option allows you to end the program.

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