| 1 | Hardware platform Code to identify the type of hardware installed in a computer environment e.g. PC, Mac, UNIX-Workstation, Mini, Mainframe. |
| 2 | Operating system Code to identify the operating system, like DOS, VMS, etc. used in a computer environment. |
| 3 | Application software Code to identify an application software, like AutoCad, Winword, etc. used in a computer environment. |
| 4 | Network Code to identify a network like Ethernet, Token Ring, etc. implemented in a computer environment. |
| 5 | Sending system Code to identify the system, which acts as a sending system in an interchange. |