UniBasic Commands Reference - Rocket Software

Parameter Description
1-535 UniBasic Commands Reference
TO file.var Specifies a file variable in which to place a pointer to the opened file.
If you do not specify file.var, the file you open becomes the default file.
UniData performs all default file operations on this file. (Default file
statements include all types of read, write, or delete when no file
variable specified).
A single default file can be declared in each UniBasic program or
subroutine, and the default file is specific to the program or subroutine
in which it is defined. If a main program opens a default file, and then
calls an display subroutine that also opens a default file, UniData
restores the original default file when returning to the main program.
ON ERROR
statements
THEN statements
END
ELSE statements
END
The ON ERROR clause enables the program to continue to perform
when a fatal error occurs such as when the file is not open, an I/O error
occurs, or UniData cannot find the file.
If a VOC entry exists for a file that does not exist, the ON ERROR
clause executes. However, if no VOC entry exists, the ELSE statement
executes.
If you do not specify the ON ERROR clause and a fatal error occurs,
the program terminates.
THEN executes if the open is successful. END is required to terminate
multiline THEN statements.
ELSE executes if the OPEN is not successful or the record does not
exist.
If the file exists, but some other error occurs, the ELSE statement
executes. However, if a file does not exist and no VOC entry exists, the
ELSE statement executes.
END is required to terminate multiline ELSE statements.
OPEN Parameters (continued)