OS/2 provides the programmable workstation platform for the delivery of Systems Application Architecture application functionality in the standalone workstation and cooperative processing environments. OS/2 overcomes the limitations of the DOS operating system by providing support for large physical and virtual address spaces and supporting concurrent execution of multiple applications with memory isolation and automated task dispatching. While enforcing memory protection between applications, OS/2 provides architected mechanisms to allow interprocess communication and data sharing in a controlled manner.
OS/2 also provides compatibility with existing DOS applications, since OS/2 Version 1.3 allows a single DOS application to run using the DOS Compatibility Box, and OS/2 Version 2.0 allows multiple concurrent DOS applications to execute in virtual DOS machines. OS/2 Version 2.0 also supports Microsoft Windows applications in a similar manner to DOS applications. This allows users of OS/2 systems to continue to use their existing DOS and Windows applications under the new operating system.
OS/2 also implements dynamic linking, which allows an application developer to isolate common application services in separate modules known as dynamic link libraries (DLLs). Calls to application services provided in a DLL are resolved at execution time, which means that any modifications to the routines contained in a DLL do not require any maintenance to applications using that DLL. In addition, DLLs are created as re-entrant code, thus allowing multiple applications to use the same memory-resident copy of the DLL code and thereby reducing storage requirements.
OS/2 provides an operating system environment for the programmable workstation that enables a far greater degree of functionality and sophistication on the part of application programs. OS/2 Version 2.0 provides architected methods for overcoming most of the inherent limitations of the DOS and OS/2 Version 1.3 environments, and providing the workstation user with a higher level of capability in the workstation. OS/2 provides the vehicle that will enable the fulfillment of the Systems Application Architecture cooperative processing direction.