10 RANDOMIZE TIMER       :   REM set random number seed to something arbitrary
20 DIM ARR(10)           :   REM initialise array
30 FOR I = 1 TO 10
40 ARR(I) = I*I          :   REM squares of the integers is OK as a demo
50 NEXT I
60 C = 1 + INT(RND*10)   :   REM  get a random index from 1 to 10 inclusive
70 PRINT ARR(C)