AMSTRAD cpc 6128 User Instruction page 313

1. Writing a character
2. Drawing the cursor 'blob'
3.· Obeying the control codes marked with an asterisk in the list ahead.
The procedure for forcing the cursor to a legal position is as follows:
1.
If the cursor is to the right of the right hand edge, then it is moved to the leftmost
column of the next line down.
2.
If the cursor is to the left ofthe left hand edge, then it is moved to the rightmost
column of the next line up.
3.
If the cursor is above the top edge, then the window is rolled down a line and the
cursor is set to the top line of the window.
4.
If the cursor is below the bottom edge, then the window is rolled up a line and the
cursor is set to the bottom line of the window.
The tests and operations are done in the order given. The illegal cursor positions may
be zero or negative, which are off to the left or above the window.
Character values in the range 0 to 31 sent to the text screen do not produce a
character on the screen but are interpreted as CONTROL CODES (and should not be
injudiciously applied). Some of the codes alter the meaning of one or more of the
following characters, which are the code's parameters.
A control code sent to the graphics screen will merely print the conventional symbol
related to its function if accessed via the keyboard (e.g. &07 'BEL' - [CTRl] G). It will
execute its control function if addressed using the form of the command:
P R I N T C H R $ ( &
0
7) ,
or P R I N T "
~
" (where the
~
is obtained by pressing
[CTRl] G within the PR I N T statement).
The codes marked
*
force the cursor to a legal position in the current window before
they are obeyed - but may leave the cursor in an illegal position. The codes and their
meanings are described with first their HEX value (&XX), then the decimal
equivalent.
Chapter 7 Page 2
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