Method and apparatus for patching code residing on a read only memory device

In an information processing system having a random access memory (RAM) device and a first version of operating software stored in a vectorized Read Only Memory (ROM) device, said first version of operating software providing a plurality of functions, said plurality of functions being implemented by a plurality of routines stored in said ROM device, wherein said plurality of routines are accessed through a vector table in said RAM device, a method for installing patches for utilizing a second version of said operating software, said method comprising the steps of:

• a) retrieving a selected patch resource, said selected patch resource comprised of a plurality of patch resource entries for replacing routines of said plurality of routines, adding new routines to functions of said plurality of functions or adding new routines for new functions not provided in said first version of operating software, each of said patch resource entries comprised of address information for identifying a vector table entry in said vector table and a routine;
• for each patch resource entry in said selected patch resource:
• b) updating said vector table entry if said patch resource entry is for replacing a routine;
• c) adding vector table entries to said vector table if said patch resource entry is for adding new routines to existing functions;
• and
• d) creating a new vector table in said RAM device if said patch resource entry is for adding new routines for new function.

A method for generating patch resource files for a plurality of previous versions of operating software based on a new version of operating software, wherein said new version of operating software is stored in a storage device, wherein each of said plurality of previous versions of operating software is stored in a vectorized Read Only Memory (ROM) device coupled to a corresponding Random Access Memory (RAM) device, wherein each of said plurality of previous versions of operating software includes a plurality of routines, each of said routines being accessed through a vector table stored in said corresponding RAM device, said method comprising the steps of:

• a) assigning a ROM version number for each ROM device, said ROM version number for each ROM device corresponding to the version of operating software residing on said each ROM device:
• b) for each version of said plurality of previous versions of operating software.
• b1) reading said previous version of operating software from the ROM device upon which said previous version is stored;
• b2) comparing the new version of operating software with the previous version of operating software;
• b3) generating a patch resource based on the differences between said previous version of operating software and said new version of operating software, said patch resource comprised of a plurality of patch resource entries, each of said patch resource entries comprising vector table addressing information and a routine, wherein said vector table addressing information of each patch resource entry indicates a location in said corresponding RAM device to store a load location of said routine, wherein said routine is a routine of said new version of operating software that differs from routines of said previous version of operating software:
• and
• b4) storing said patch resource on a digital storage device.

A method for updating a first operating software stored in a read only memory (ROM) device based on a second operating software, wherein said first operating software includes a first plurality of routines, wherein said first operating software provides a first plurality of functions, wherein said second operating software includes a second plurality of routines, wherein said second operating software provides a second plurality of functions, the method comprising the steps of:

• storing in a random access memory (RAM) device a plurality of vector tables, wherein each vector table corresponds to a function of said first plurality of functions;
• storing in each vector table a plurality of vector table entries, wherein each vector table entry of said plurality of vector table entries includes a reference to one of said first plurality of routines stored in said ROM device;
• comparing said first plurality of routines to said second plurality of routines to determine a set of modified routines, said set of modified routines being routines of said first plurality of routines that correspond to but are different from a routine in said second plurality of routines;
• for each modified routine in said set of modified routines
• determining the vector table entry of said plurality of vector table entries that refers to said modified routine;
• and
• updating said reference in said vector table entry to cause said reference to point to said routine of said second plurality of routines that corresponds to said modified routine.