VMS Help MACRO, VAX MACRO Assembler, Instructions, INDEX  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Purpose:        Index calculation of arrays of fixed length data, bit
                    fields and strings
    Format:         opcode subscript.rl,low.rl,high.rl,size.rl,indexin.rl,
                           indexout.rl
    Operation:      indexout = {indexin + subscript}*size; if {subscript
                    LSS low} or {subscript GTR high} then {subscript
                    range trap}
    C. Codes:       N = {indexout LSS 0}, Z = {indexout EQL 0},
                    V = 0, C = 0
    Exceptions:     Subscript range
    Opcode:         0A    INDEX    Index
    Description:    indexin is added to subscript and the sum is multiplied
                    by size. The result is placed in indexout. If subscript
                    is less than low or greater than high a subscript range
                    trap is taken.