Commodore 128D User Manual page 263

DCLEAR
i i
DCLOSE
DEFFN
/ \
—Clear all open channels on disk drive
DCLEAR [Ddrive number][<ON | ,>Udevice]
This statement closes all files and clears all open channels on the
specified device number. Default is DO, U8. This command is analag-
oustoOPEN 10,8,15, "IO":CLOSE 10.
EXAMPLES:
DCLEAR DO
DCLEAR D1,U9
Clears all open files on drive 0,
device number 8.
Clears all open files (channels) on
drive 1, device number 9.
—Close disk file
DCLOSE [#logical file number][<ON | ,)Udevice]
This statement closes a single file or all the files currently open on
a disk unit. If no logical file number is specified, all currently open
files on the designated drive are closed. The default device number
is 8. Note the following examples:
EXAMPLES:
DCLOSE
DCLOSE #2
DCLOSE U9
Closes all files currently open on unit 8.
Closes the file associated with the logical file
number 2 on unit 8.
Closes all files currently open on unit 9.
—Return the value of a user-defined function
DEF FN name (variable) = expression
This statement allows the definition of a complex calculation as a
function. In the case of a long formula that is used several times
within a program, this keyword can save valuable program space.
The name given to the function begins with the letters FN, followed
by any alphanumeric name beginning with a letter. First, define the
function by using the statement DEF, followed by the name given to
the function. Following the name is a set of parentheses () with a
dummy numeric variable name (in this case, X) enclosed. Next is an
equal sign, followed by the formula to be defined. The function can
be performed by substituting any number for X, using the format
shown in line 20 of the example below:
255
BASIC 7.0 ENCYCLOPEDIA—Basic Commands and Statements