Commodore Plus 4 - Page 181

Redefining the Function Keys 169
when you want to use such a function on a number, first use STR$ to convert the
number to a text string.
Example: T$ = STR$(T): IP RIGHT$(T$,3) The STR$ function converts the
= ".99" THEM" T = T + .01 numeric value of T into a string called
T$. The RIGHTS function reads the
three rightmost characters of T$. If
these characters equal .99, .01 is
added to the value of T.
After you convert a number to a text string, the number loses its numeric
properties, which means you cannot use the number in a calculation. Instead, the
computer treats the stringified number the same way it treats any text string.
After you finish using the number as a text string, you can change it back to a
numeric value by using the VAL function.
The VAL function converts numbers in a string into a numeric value. You can
use VAL to reverse a STR$ function or to extract numbers from any text-string
expression.
When you use VAL on a text string that contains both numbers and non-
numeric characters, the computer converts only the numbers up to the first
nonnumeric character. For example, if you issue the command PRINT
VAL("34R5"), the computer displays only 34; the 5 after the R is not displayed
because the first nonnumeric character turns off the VAL function.
Redefining the Function Keys
You can redefine a function key at any time in immediate mode or within a
program. Any definitions you write are erased from computer memory when you
turn off or reset the computer (unless you hold down the RUN/ STOP key during
the reset). The KEY command lets you write a definition for a function key. The
KEY command also displays the current definitions of the function keys; all
redefinitions written during the current computing session are displayed in this
list.
Follow these steps to redefine a function key:
STEP 1 Type KEY and the key number (to define the HELP key, type an 8)
followed by a comma.
STEP 2 Type the text string for the key definition:
You can define the key to perform multiple tasks in BASIC. Link multiple
BASIC commands and/or functions with plus signs.
If a literal constant string is used for a key definition, it must be in quotes.