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.