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
Use the Unlock procedure in situations where more than one part of your program may need read and write access to the same data file. The Unlock procedure removes a lock that the Lock procedure placed on a section of the file or the whole file.
Use the Unlock procedure only with the
filenumber parameter to unlock the whole
The Unlock procedure unlocks an entire file
opened in Input or Output (sequential) mode, regardless of the
Records and bytes in a file are always numbered sequentially from 1 up.
To unlock a particular record, specify its record number as
record, and only that record will be
To unlock a range of bytes (in a binary file) or of records (in a
random file), indicate the starting position as
fromrecord and the ending position as
You must take care to remove all file locks using the Unlock procedure before either closing a file or ending the application; otherwise, you can leave the file in an unstable state. This means that, where appropriate, your error-handling ...