Commodore VIC-20 User Manual page 381

Example:
655 STOP
VALIDATE
Format:
Appendix G: BASIC Statements
367
Will cause the message BREAK IN 655
to be displayed
PRINT#lf,"V[ALIDATE][dr]"
The diskette in drive
dr
is validated.
If
the
dr
parameter is absent, the
diskette in the most recently selected drive is validated.
When a diskette is validated, a new Block Availability Map is created
for all valid data files on the diskette. Any files that were improperly closed
or were not closed become invalid files; they are deleted from the diskette
and their diskette space is released.
Do not validate a diskette that contains random access files; validation
will erase the random access file. If a read error occurs during validation, the
validation operation is aborted and the diskette is left in its initial state. A
diskette must be initialized after it is validated.
Example:
OPEN 1,8,15
Open the diskette command channel
PRINTlU,
"10" Initialize the diskette in drive 0
PRINTiL "VO"
Validate the diskette in drive 0
VERIFY
The VERIFY statement compares the current program in memory with
the contents of a program file.
CGsseHe Unit Format
VERIFY [':rile name'1[,dev]
The program currently in memory is compared with the program
namedfile name on the cassette in the unit specified by dev. If dev is not
present, a default of I is assumed and cassette unit 1 is selected. Iffile name is
not present, the next file on the cassette in the selected unit is verified.
You should always verify a program immediately after saving it. The
VERIFY statement is almost always executed in immediate mode.