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Foreign !:

J interfaces with the environment are provided by the conjunction!: (foreign). In most cases the foreign result is a verb that provides a specific service. The left argument of foreign selects a general family of services and the right argument selects a specific service. The families of services selected by the left argument are:
  0  scripts
  1  files
  2  host commands
  3  types
  4  names
  5  representations
  6  time
  7  space
  9  global parameters
 11  windows
 13  debug
 15  dynamic link library (shared library)
 18  locales
128  numerical functions
The foreign conjunction is documented in the J Dictionary.

You have run across a few specific uses of the foreign conjunction in earlier sections.

The derived verb 9!:11 was used in the Print precision section. The 9 selects the global parameters family and the 11 gives a derived verb that sets the print precision.

The load verb uses 0!:0 to load scripts. The left argument selects the scripts family. Look up the definition. The 0 right argument is treated as three decimal digits 000 and therefore executes sentences from a file, stops on an error, and is silent (does not display sentences or results).

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