HP 10413 Datasheet download pdf (Page 231)

231

The DISPXY command allows you to place a string of text at any position on

the screen using two different fonts. Until this command was added to the

language the only way to do this was to:

- save the current screen into a graphics variable.

- create a special GROB which contained the text.

- superimpose the GROB onto the stored image.

- redisplay the modified image onto the screen.

Quite apart from the fact that this was incredibly involved, it was very slow

and the command to create the GROB was very limited in what it would

allow.

The new command has the syntax:

DISPXY <x-pos>;<y-pos>;<font#>;<object>:

Suppose M=2 & C=3. Then the command

will display the text “y=2x+3” using font #1 (small) at the top (Ymax) left

(Xmin) of the screen.

The next line places a label on the y axis (offset slightly) to mark the y-

intercept. A check is then done to see if an x-intercept exists and, if it does, a

label is placed to mark it. Any labels off the edge of the screen will be

ignored.

Finally the line itself is drawn. Even though part of the line extends off the

screen there is no problem - the excess is clipped.

The next section of code below waits until the user presses a key (GETKEY)

and stores the key’s code into the variable K.

A CASE statement is then used to check for the use of the arrow keys. Notice

the lack of colons (:) after each END in the CASE statement.

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HP 10413 Datasheet Page 231