Forward indexing

To index forward through an array (from low to high storage addresses), you need a BXLE test, to end the loop when the highest address is reached. If no explicit terminator is specified, and if none of the preceding combinations of keywords and values exist, then forward indexing is assumed, and a BXLE terminator is generated.

        DO  FROM=(Rx,1),TO=(Ry+1,10),BY=(Ry,2)
          Code for F
        ENDDO

        DO  FROM=(R1,1),TO=(R3,10),BY=(R2,2)
          LA    R1,1
          LA    R3,10
          LA    R2,2
#@LB2     DC    0H
          Code for F
        ENDDO
#@LB3     DC    0H
          BXLE  R1,R2,#@LB2