You can define global variables only with DECLARE statements
       entered in response to the DTR> prompt of DEC DATATRIEVE command
       level.

       You can use a global variable as a value expression in any DEC
       DATATRIEVE statement. Unless you define a global variable with
       a COMPUTED BY clause, the global variable retains the value you
       assign to it until you either assign it a new value or release it
       with the RELEASE command.

       The value of a global variable defined with a COMPUTED BY clause
       depends on the value expression that controls the computation.
       For example, you can declare the value of the variable to be 1.2
       times the price of a boat in the YACHTS domain. The value of the
       variable changes according to the value of the PRICE field for
       different records:

       DTR> READY YACHTS
       DTR> DECLARE VAR COMPUTED BY PRICE * 1.2.
       DTR> FOR FIRST 5 YACHTS PRINT VAR USING $$$,$$$.99

          VAR

       $44,341.20
       $21,480.00
       $33,000.00
       $22,320.00
       $11,874.00

       DTR>