The concept of execution environment is an essential part of the definition of software reliability. Consider that a software system supports 10 different functions f1,...,f10, and there are two groups of users. One group of users use only functions f1,...,f7, and the second group uses all the functions. Let functions f1,....,f7 be fault free, but there are faults in functions f8, f9, f10.
function a. the kind of action or activity proper to a person, thing, or institution; the purpose for which something is designed or exists
b. mathematical functions
c. function keys
Everyone I talked to takes the word function in this context to mean one of the above three. Which do you think is right?