NCL Statement Types and Syntax › Label Statements › Undefined Labels

Undefined Labels

Normally, an attempt to branch to an undefined label results in an error and the procedure is terminated. However, the &CONTROL NOLABEL operand lets the user specify that an attempt to branch to an undefined label will not result in an error, but will simply drop through and execute the statement following the &GOTO. Thus, a trap for unexpected messages can be set up and all of the efficiencies associated with direct branching still achieved.

Example: Undefined Labels

&CONTROL NOLABEL
.NEXT
     &PPOREAD VARS=(A,B,C,D,E)
     &GOTO .&A
     &WRITE ALARM=YES DATA=UNEXPECTED INPUT &A &B &C &D &E
     &GOTO .NEXT
.IST305I
.IST314I
     .
     .
     .