Any valid file number
The record or byte number at which to commence the lock
The first record or byte number to lock
The last record or byte number to lock
The Lock procedure prevents another process from accessing a record, section, or whole file until it is unlocked by the Unlock function.
Use the Lock procedure in situations where multiple programs or more than one instance of your program may need read and write access to the same data file.
Use the Lock procedure with only the
filenumber argument to lock the whole
record is interpreted as a record number
in the case of random files and a byte number in the case of binary
files. Records and bytes in a file are always numbered sequentially
from 1 onward.
To lock a particular record, specify its record number as
record, and only that record will be
The Lock procedure locks an entire file opened
in Input or Output (sequential) mode, regardless of the
If you omit the
Lock will lock all records from the start of the
file to record or byte number
Attempting to access a locked file or portion of a file returns runtime error 70, “Permission denied.”
You must take care to remove all file locks ...