14 CTRL This key behaves similarly to the SHIFT key in that it can be used to change the character generated by other keys. For example, pressing CTRL and G (called Control G) makes the internal speaker make a short noise. CTRL B is used to turn a printer on and CTRL C turns it off. CTRL N makes the computer stop at the bottom of each page, etc, etc. More information on control codes is given in chapter 34. TAB Another key that is useful in special circumstances – like word processing. These keys can be somewhat confusing because they seem to generate the wrong characters sometimes.
The problem is that there are two international standards for displayed characters (Teletext and ASCII) and the BBC Microcomputer can display either. MODE 7 generates the Teletext display characters and MODES 0 to 6 show the ASCII characters. But don’t worry, the computer recognises the key correctly regardless of what is displayed on the screen. Here is a table showing all these characters: Note that in MODE 7 a zero is shown as a rather pointed O whereas in all other modes, zeros have a slash – 0 – to help to differentiate them from the letter O . The keyboard is also marked in this way. On the key Displayed on the screen in MODE 7 in MODES 0 to 6 ~ ^ ¦ \ { [ } ] ÷ 9 R ½ ¼ 8 ¾ :
~ ^ ¦ \ { [ } ]