Объекты IBM i: Типы и особенности

On many computing platforms everything is a file, but in contrast in IBM i everything is an object.

IBM i objects share similarities with objects in object oriented programming, but there are differences as well. There are similarities in 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. There are differences in that IBM i objects cannot be inherited, and the set of object types is fixed, and only IBM has the ability to create new ones. 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 more 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 Control Language for more information. *MENU: Menu (accessed with the GO command). *FILE: File (IBM i files can be used for data, input/output devices, and source code, depending on sub type). *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). *USRSPC: User space a generic data containing object of arbitrary size (up to 16T).

A library (*LIB) on IBM i is an object that is used as a system directory to keep track of other objects. Objects are not stored inside libraries, but rather libraries are used as namespaces for objects. Libraries are a "system" object, and therefore only one instance of any given Library "name" is possible. They're made to appear as if they're stored in the QSYS library.