Abstract: A multiprogramming data processing system comprises a plurality of data processing devices P1, P2, P3, P4 each having local storage 110-116 and has furthermore an interconnecting standard bus 100. The program is divided in program segments S1-S4, while the program segments are grouped into program portions (k, m, n). The respective program portions are each stored at one of the local memory sections. When an extended branch instruction calls an address in a different program portion, a portion change interrupt signal (26) is generated, whereby dynamical allocation of the execution of program segments may be realized. When a privileged portion (0) is called, the portion change interrupt is nullified, both at the calling to, (28) and the return (23) from the privileged program portion.