AS/400 object

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On most other platforms everything is a file. On the AS/400 everything is an object. This seems to be the same as object-oriented programming, but with the AS/400 it's different. The similarity is that when storage is allocated for something, that something is of a specific type, and only a specific set of programs are allowed to act upon that object. The dissimilarity is that even though the AS/400 supports Java and C++, these objects cannot be inherited like the classes in those languages.

The number of object types is huge and a small subset of them are available to users. The human readable form of the object type is always a three to six character mnemonic preceded by an asterisk. What follows is a short list of the most commonly used objects and their mnemonics:

  • *LIB: Library (where everything below, except directories and stream files, is stored; libraries cannot exist within other libraries)
  • *PGM: Program (for compiled languages: CL, RPG-IV, C, C++, COBOL, etc. and there are no interface restrictions between the languages).
  • *MODULE: Module (linkable into a program from a compiled language above and here too there are no restrictions on linkability between languages).
  • *SRVPGM: Service program (dynamic set of one or more modules, akin to a DLL file in Microsoft Windows).
  • *BNDDIR: Binding directory (holds a list of modules and service programs and is used when creating programs).
  • *CMD: Command (an object used for calling programs that allows users to prompt for their parameters; can be created with the Command Definition language). See AS/400 Control Language for more information.
  • *MENU: Menu (accessed with the GO command).
  • *FILE: File (for both devices, data, and program source; described with DDS; data files can also be created with SQL).
  • *DTAARA: Data area (small bits of storage used to store tiny items of data for fast access).
  • *DIR: Directory (part of the Integrated File System that is equivalent to Unix and Microsoft Windows hierarchical file systems).
  • *STMF: Stream file (traditional file that would be familiar to most Unix and Microsoft Windows users and only stored in directories)
  • *JRN & *JRNRCV: Journal and journal receiver (used to journal changes to files, data areas, and stream files).
  • *USRPRF: User profile (allows users to sign-on to the system).
  • *JOBD: Job description (used when submitting/starting jobs).
  • *SBSD: Subsystem description (used when starting subsystems; this is the place where user jobs run).
  • *JOBQ: Job queue (used to queue up batch jobs to run in a subsystem).
  • *LIND: Line description (communications line: Ethernet, token ring, etc).
  • *CTLD: Controller description (communications controller for lines, workstations, etc.).
  • *DEVD: Device description (communications device for lines, workstations, printers tape drives, etc.)
  • *DTAQ: Data queue (used to queue up data entries for fast retrieval by other jobs).
  • *MSGQ: Message queue (used to send message to users, can also be used like a data queue).
  • *OUTQ: Output queue (used to queue up output to a printer).

Creating an object usually (but not always) involves a command that begins with the mnemonic "CRT". So, to create a job description you would prompt the CRTJOBD command. User profiles would be created with the CRTUSRPRF command. Similarly changing objects is done by prompting commands preceded by "CHG" (CHGJOBD, CHGUSRPRF, etc.), deleting an object uses "DLT" (DLTJOBD, DLTUSRPRF, etc.), displaying an object uses "DSP" (DSPJOBD, DSPUSRPRF, etc.), and working with a set of objects uses "WRK" (WRKJOBD, WRKUSRPRF, etc.). To view a generic set of objects in a library use the DSPOBJD command. WRKOBJ can be used to view objects in multiple libraries.