bas7advr.hlp (Topic list)
ERR Statement Details
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Sets ERR to a specific value.
 
ERR = n%
 
Usage Notes
    ■ When running an application program, BASIC uses ERR to record whether
      or not a run-time error has occurred and what the error was. When the
      program starts running, ERR is 0; when and if a run-time error
      occurs, BASIC sets ERR to the error code for that error.
    ■ You may want to use the ERR statement to set ERR to a non-zero value
      to communicate error information between procedures. For example, you
      might use one of the run-time codes not used by BASIC as an
      application-specific error code. See Table 4.1, Run-Time Error
      Codes, in the BASIC Language Reference, for a list of the run-time
      error codes that BASIC uses; they are a subset of the integers
      between 1 and 255, inclusive.
    ■ Besides the ERR statement, the following BASIC statements set ERR
      whenever they execute:
        - Any form of the RESUME statement sets ERR to  0.
        - EXIT SUB, EXIT FUNCTION, or EXIT DEF set ERR to 0 if executed
          within a procedure-level error handler.
        - All uses of the ON ERROR or ON LOCAL ERROR statements syntax
          set ERR to 0.
        - The ERROR statement can be used to set ERR to any value as
          part of simulating any run-time error.