Field counts must be literal integers, that is, they cannot be scalar variables. Field counts are specified by an integer preceding the vector name. For example, READ FILE.DAT 3X 2Y Z will read 6 numbers from each record, placing the first 3 numbers into X[i], X[i+1], X[i+2], the next 2 numbers into Y[i], Y[i+1], and the last number into Z[i]. This command is equivalent to READ FILE.DAT X X X Y Y Z.