 By carefully using blocks of line numbers that do not overlap, programmers can build libraries of subroutines and merge them into new programs as needed.Atari BASIC can call machine code subroutines.The machine code is generally stored in strings, which can be anywhere in memory so the code needs to be position independent, or in the 256-byte Page 6 area (starting at address 153610, 60016), which is not used by BASIC or the operating system.