Casio IT-2000D - Manual (Page 158)

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Clearing the buffer
If the key buffer clear command is issued while the keypad is being touched, processing for the
current operation will also be canceled. For example, a reverse-video display will be restored to
normal, and no new key inputs will be permitted until the pen (or user's finger) is removed from the
panel.
Input of ten key while the screen is being touched
If a ten key is pressed while the user screen is being touched, the character code corresponding to
the ten key will be logged in the interval from when the down coordinates are acquired to when the
up coordinates are acquired.
Registering an expanded key
The user can register a keycode and its key face image for the EXT1 and EXT2 keys. Since the
registered contents can be stored in a specific area in the driver, the application program does not
have to store them. Expanded keys keycodes 01h to FFh can be registered. Scanning codes can also
be registered, however, they cannot be acquired through the input function.
Restrictions and notes on use of keycodes

Do not use the dedicated input functions and standard input functions concurrently.
For the standard input functions no interface is provided to log coordinate data, since they are
called via the DOS system. If the standard input function is called from DOS, the coordinate data
obtained will be redundant. Therefore, if the standard input function is called after the dedicated
input function acquires the down coordinates, acquisition of the up coordinates will be hampered.
If a key scanning reports "data present" as the result of using the dedicated input function, and if
the data obtained through the standard input function is coordinate data, it is assumed that there is
no corresponding key.
If this is the case, the program cannot return from the standard input function. This means that an
application program must not contain both the input functions. It is even possible to create an
application using only the standard input functions if the application does not use any coordinate
data. However, use of the dedicated input functions is recommended.

There may be a case where the up status cannot be acquired and the cancel status data is returned.
The up coordinates may not be returned if the power is turned off after the down status has been
acquired. In this case the cancel status will be returned. Take this possibility into account when
creating applications. It is especially important to exercise care when creating a program which
accepts the result of an action when the pen is up.