A method of operating a computer system includes providing a first version of
a
program in memory and verifying the program prior to program execution. Program
verification includes indicating a verification error when a first version of a
first program unit implementation is not internally consistent, indicating a verification
error when the first version of the first program unit implementation is inconsistent
with the version of the program unit API definition file associated with the first
version of the first program unit implementation, receiving a second version of
the first program unit implementation and a second version of the first program
unit implementation is binary compatible with the first version of the first program
unit implementation by comparing the first version of the first program unit API
definition file and the second version of the first program unit API definition unit.