Sinclair ZX Spectrum Introduction Manual page 11

in the double quotation marks onto the screen. For this command to be executed
by the computer, the ENTER key must be used. When this has been done the
screen should display the word
and some other characters. (A flashing question mark indicates a mistake
somewhere. If this happens start again and repeat the exercise). The message at
the bottom is really the computer reporting back that everything has gone 'OK'. The
message is important when running programs but can be ignored at the moment.
Notice something else: The letter O and the numeral 0 are represented by
different characters. It is important to remember this, The numeral 0 always has a
line through it. The computer will always interpret the letter O as a letter, so don't
press the wrong key. Similarly, the numeral 1 and the lower case letter L are
different and unlike some typewriters, these cannot be interchanged.
As the keyboard mode is so important to understand it is useful to summarise
what happens once again.
The flashing character
the computer will put the next thing that you type. It is not always an L; if you turn
the computer oft and on and then press ENTER the copyright message will change
into a K cursor. The letter that it uses tells you how the computer will interpret the
next thing that you type. At the beginning of a Line it will be a flashing
for 'keyword'. (The copyright message and reports also count as a flashing K) A
keyword is one of the computer's special words, occurring at the beginning of a
command to give the computer a general idea of what the command is going to tell
it to do. Since the computer is expecting a keyword at the beginning of a line, when
you press - say - the P key the computer decides not to interpret this as a P but as
PRINT; and it warns you that it is going to do this by making the cursor a K. When
it has the first keyword, it doesn't expect another one so what you type now will be
interpreted as letters. To show this, the computer changes the cursor to an
'letter'.
These different states are often called modes - we shall talk about keyword (or K)
mode, and letter (or L) mode.
If you want to type a lot of capital letters without holding CAPS SHIFT down, you
can make all letters come out as capitals by first pressing CAPS LOCK (CAPS
SHIFT with 2). To show this is happening, the
flashing C (for 'capitals'). To get lower case letters and the
CAPS LOCK a second time.
(If you press CAPS LOCK during keyword mode, you will not immediately notice
any difference, but you will see the effect after entering the keyword when the
computer will be in C mode instead of L mode).
As well as keywords, letters, numbers and various programming and scientific
expressions, the keyboard also has eight graphics characters. These appear on the
number keys 1 to 8, and can be printed onto the screen in a similar way to letters
and numbers. To do this the keyboard must be changed to graphics mode. This is
Hello
L is called the cursor. It shows whereabouts on the screen
L cursor will be replaced by a
L cursor back, press
Chapter 2
K standing
L - for
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