Figure 4.3 shows a (very) small sample behavior file. Every line that begins with an ``I'' corresponds to a function entry and every line that begins with an ``O'' corresponds to a function exit. The number on each line is the time, in microseconds, from the beginning of program execution that the corresponding entry or exit occurred. For function entries, the function name is given. The names are not needed for function exits because a stack based implementation is assumed.
This program trace gives enough information for us to simulate executing the program with our continuous compilation model. How this simulation is accomplished is described in the next section.