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


{{PageSyntax}}
:[[LOCK]] [#]{{Parameter|fileNumber%}}
:[[LOCK]] [#]{{Parameter|fileNumber%}}, {{Parameter|record&}}
:[[LOCK]] [#]{{Parameter|fileNumber%}}, [{{Parameter|firstRecord&}}] TO {{Parameter|lastRecord&}}


{{PageDescription}}
* {{Parameter|fileNumber%}} is the file number of the file to lock.
* In the first syntax, the entire file is locked.
* In the second syntax, {{Parameter|record&}} is the record number of the file to lock.
* In the third syntax, the records or bytes in the range [{{Parameter|firstRecord&}},{{Parameter|lastRecord&}}] are locked. If {{Parameter|firstRecord&}} is omitted, it is assumed to be one (the first record or byte).
* For files opened in [[BINARY]] mode, each record corresponds to a single byte.
* [[LOCK]] and [[UNLOCK]] statements are always used in pairs and each statement must match the other one.
* Files must be unlocked using [[UNLOCK]] before other programs can access them, and before the file is closed.
* [[Keywords_currently_not_supported_by_QB64#Keywords_Not_Supported_in_Linux_or_MAC_OSX_versions|Keyword not supported in Linux or macOS versions]]


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


{{PageSeeAlso}}
* [[UNLOCK]]
* [[OPEN]]
* [[ACCESS]]


{{PageNavigation}}