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# Locked Scripts (ijl files)

The J development system can load definitions from a locked script file. The names defined by running a locked file can be used normally, but their definitions are hidden from the user. A locked file normally has a file suffix of `.ijl`. This allows you to use proprietary or protected definitions within the framework of an open J development system. Source is locked with verb `3!:6`, for example:``

       dat=. fread 'user\projects\util\myapp.ijs' NB. read source
       dat=. 3!:6 dat                             NB. lock source
       dat fwrite 'user\projects\util\myapp.ijl'  NB. create ijl file

The text for `abc.ijl` is encoded and running it defines its verbs,adverbs, and conjunctions as locked. Locked definitions will not be disclosed by the J interpreter. For example, create `foo.ijs` and `foo.ijl` with the following definitions:

       plus =: 4 : 'x.+y.'
       mean =: 3 : '(plus/y.)%#y.'
       plust=: +
       meant=: plust/ % #

Load and test as:

       0!:1 <'foo.ijs'             |    0!:1 <'foo.ijl'
       3 plus 'abc'                |    3 plus 'abc'
    |domain error: plus            | |domain error: plus
    |   x.    +y.                  | |   3     plus'abc'
       mean 'abc'                  |    mean 'abc'
    |domain error: plus            | |domain error: plus
    |   x.    +y.                  | |   mean    'abc'
       13!:0 [1                    |    13!:0 [1
       mean 'abc'                  |    mean 'abc'
    |domain error: plus            | |domain error: plus
    |   x.    +y.                  | |   mean    'abc'
    |plus[:0]                      |
          13!:1 ''                 |    13!:1 ''
    |domain error                  |
    |   x.    +y.                  |
    |plus[:0]                      |
    |   (    plus/y.)%#y.          |
    |mean[0]                       |
    |       mean'abc'              |
                                   |

          13!:0 [1                 |    13!:0 [1
       plus                        |    plus
    4 : 'x.+y.'                    | plus
       meant f.                    |    meant f.
    +/ % #                         | meant

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