[Patents] EPO multitasking patent

[PILCH Hartmut phm@a2e.de]

EP0644483 
Computer system and method for performing multiple tasks. 
IBM (US)


   Claims
   
   1. Computer system for performing multiple tasks, said computer system
   comprising at least one terminal T, at least one applications program
   Ai and a communication subsystem (3),
   characterized in that
   a dedicated virtual terminal VTi (4) is assignable to said
   applications program Ai,
   a logical connection Li is establishable via said communication
   subsystem between said applications program Ai and its dedicated
   virtual terminal VTi (4, 9), and in that
   said logical connection Li is adapted to be maintained independently
   from the existence of a logical connection liT between said terminal T
   and said dedicated virtual terminal VTi.
   2. Computer system according to claim 1, characterized in that
   said dedicated virtual terminal VTi (4) having a dedicated control
   block Bi assigned thereto,
   said terminal T having a dedicated terminal control block BT assigned
   thereto,
   wherein said logical connection liT between said terminal T and said
   dedicated virtual terminal VTi is establishable by storage of a first
   pointer PiT in said control block Bi and storage of a second pointer
   PTi in said terminal control block BT, said first pointer PiT pointing
   to said terminal control block BT and said second pointer PTi pointing
   to said control block Bi.
   3. Computer system according claim 2, characterized in that said first
   pointer PiT being a null pointer if said logical connection liT
   between said terminal T and said dedicated virtual terminal VTi is not
   established.
   4. Computer system according to any one of the preceding claims,
   characterized in that a dedicated virtual terminal VTT is assigned to
   said terminal T and said terminal control block BT preferably
   comprises a virtual terminal pointer PT which points to said dedicated
   virtual terminal VTT of said terminal T.
   5. Computer system according to any one of the preceding claims,
   characterized in that said computer system further comprises a user
   simulation program (7) and a dedicated virtual terminal VTc (14) which
   is assigned to said user simulation program,
   whereby a logical connection Ci (C1, C2) between said user simulation
   program and said dedicated virtual terminal VTi of said application
   program is establishable under to the control of said user simulation
   program, and
   a logical connection CT between said terminal T and said dedicated
   virtual terminal VTC is establishable
   6. Computer system according to claim 5, characterized in that said
   logical connection Ci between said user simulation program and said
   dedicated virtual terminal VTi of said applications program Ai is
   establishable by storage of a third pointer Pic in said control block
   Bi and storage of a fourth pointer Pci in a storage location which is
   assigned to said user simulation program, said third pointer Pic
   pointing to said user simulation program and said fourth pointer Pci
   pointing to said program specific control block Bi.
   7. Computer system according to claim 5 or 6, characterized in that
   said logical connection CT between said terminal T and said dedicated
   virtual terminal VTc of said user simulation program is establishable
   by storage of a fifth pointer PTC in said terminal control block BT
   and by storage of a sixth pointer PCT in a storage location assigned
   to said user simulation program, said fifth pointer PTC pointing to
   said user simulation program and said sixth pointer PCT pointing to
   said terminal specific control block BT.
   8. Computer system according to any one of the preceding claims,
   characterized in that said computer system comprises a plurality of
   host computers and at least two applications programs Ai, Aj which are
   stored on different ones of said host computers, each of said
   applications programs Ai, Aj having a dedicated virtual terminal VTi,
   VTj (4, 9) assigned thereto,
   said dedicated virtual terminals VTi, VTj being stored in one of said
   host computers.
   9. Computer system according to any one of the preceding claims,
   characterized in that said logical connections are establishable by
   means of a virtual telecommunications access method.
   10. Method for performing multiple tasks in a computer system, said
   computer system comprising a terminal T and a plurality of application
   programs and a communication subsystem (3), said method being
   characterized by the following steps:
   a) selecting an applications program Ai out of said plurality of
   application programs,
   b) establishing of a logical connection Li via said communication
   subsystem between said applications program Ai and a dedicated virtual
   terminal VTi (4, 9),
   c) establishing a logical connection liT between said terminal T and
   said dedicated virtual terminal VTi, and
   d) maintaining said logical connection Li independently from the
   existence of said logical connection liT.
   11. Method according to claim 10, characterized in that said logical
   connection Li is established by
   a) assigning a dedicated control block Bi (B1, B2) to said dedicated
   virtual terminal VTi,
   b) assigning a dedicated terminal control block BT to said terminal T,
   c) storing a first pointer PiT in said control block Bi,
   d) storing of a second pointer PTi in said terminal control block BT,
   whereby said first pointer PiT points to said terminal control block
   BT and said second pointer PTi points to said control block Bi.
   12. Method according to claim 10 or 11, said computer system further
   comprising a user simulation program (7) and a dedicated virtual
   terminal VTc (14) which is assigned to said user simulation program,
   said method being characterized by the following steps:
   a) selecting an applications program Aj out of said plurality of
   application programs,
   b) selectively establishing one or more logical connections Ci, Cj
   between said user simulation program and said dedicated virtual
   terminals VTi, VTj of said applications programs Ai, Aj,
   c) selectively establishing a logical connection CT between said
   terminal T and said dedicated virtual terminal VTc of said user
   simulation program.
   13. Computer system or method according to any one of the preceding
   claims, characterized in that said dedicated virtual terminal
   comprises a virtual terminal buffer VTA1, VTA2, VTT1 which is stored
   in a main memory of said computer system independently from the
   existence of a logical connection between said terminal T or - if
   present - said user simulation program and said dedicated virtual
   terminal.
     _________________________________________________________________
   
   Data supplied from the esp@cenet database - l2