The invention relates to a computer system and method for performing multiple tasks. The computer system comprises a host (2), a communication subsystem (3), a plurality of application programs (1, 2), virtual terminal manager (5), virtual terminals (9, 4), an application programming interface (6), and a cross application program (7) as well as a real terminal T. The logical connections L1, L2 of the application programs to their associated virtual terminals are independent from the logical connections of the respective virtual terminals to the real terminal T. The logical connections l3T, l2T are user selectable by positioning of the software controllable switch 11. A plurality of application programs, for example applications programs (A1, A2), are integrated by the cross application program (7) which has access to the respective virtual terminals (4, 9) via the application programming interface (6) and the virtual terminal manager (5). The cross application program (7) can also be used for user simulation in order to automate the operation of the integrated application programs.