The [LOCK](LOCK) statement restricts access to parts of a file by other programs or processes.


## Syntax

> [LOCK](LOCK) [#]fileNumber%
> [LOCK](LOCK) [#]fileNumber%, record&
> [LOCK](LOCK) [#]fileNumber%, [firstRecord&] TO lastRecord&


## Description

* fileNumber% is the file number of the file to lock.
* In the first syntax, the entire file is locked.
* In the second syntax, record& is the record number of the file to lock.
* In the third syntax, the records or bytes in the range [firstRecord&,lastRecord&] are locked. If firstRecord& is omitted, it is assumed to be one (the first record or byte).
* For files opened in [BINARY](BINARY) mode, each record corresponds to a single byte.
* [LOCK](LOCK) and [UNLOCK](UNLOCK) statements are always used in pairs and each statement must match the other one.
* Files must be unlocked using [UNLOCK](UNLOCK) before other programs can access them, and before the file is closed.
* [Keywords currently not supported](Keywords-currently-not-supported-by-QB64)


## QBasic/QuickBASIC

* Required DOS **SHARED.EXE** to be run for QBasic to use networking access modes. No longer required.


## See Also

* [UNLOCK](UNLOCK)
* [OPEN](OPEN)
* [ACCESS](ACCESS)