Method and apparatus for introducing program changes in program-controlled systems

In a program-controlled processor system wherein processes are initiated and executed by function calls to program functions stored in a program memory, means for modifying program functions during the execution of said processes, said means comprising:

• means for storing a system sequence number;
• means associated with each process for storing a process sequence number;
• means for storing a current version of a selected one of said program functions;
• means for storing a modified version of said selected one of said program functions;
• means for storing a decision function sequence number associated with said modified version;
• processor means, operative under the control of instructions stored therein to store said current version in said means for storing said current version, to store said modified version in said means for storing said modified version, to generate and store a quantity in said means for storing a system sequence number, to copy said system sequence number into said means for storing a process sequence number when the associated process is initiated, at the time said modified version is stored, to store in said means for storing a decision function sequence number a quantity whose value exceeds at said time said modified version is stored the value of any process sequence number in a given direction, to change said system sequence number so that it reaches a value at least as far in said given direction as said decision function sequence number, to initiate execution of said current version of said selected function in response to a function call by a calling process to said selected function if the process sequence number of said calling process is before said decision function sequence number in said given direction and to initiate execution of said modified version of said selected function in response to a function call by said calling process to said selected function if the process sequence number of said calling process is at least as far as said decision function sequence number in said given direction.

In a program-controlled processor system, wherein task processes are initiated and are executed by function calls to program functions stored in a program memory,

• means for modifying a selected program function during the execution of task processes said means comprising:
• first means for storing a current version of said selected program function;
• second means for storing a modified version of said selected program function;
• third means for storing data defining an activation time after which said modified version of said selected program function is to be used;
• and
• means for initiating execution of said current version if a process calling said program function was initiated before said activation time, and for initiating execution of said modified version if said process calling said selected program function was initiated after said activation time.