Consider a language implementation in which we wish to catch every use of an uninitialized variable. In Section 6.1.3 we noted that for types in which every possible bit pattern represents a valid value, extra space must be used to hold an initialized/uninitialized flag. Dynamic checks in such a system can be expensive, largely because of the address calculations needed to access the flags. We can reduce the cost in the common case by having the compiler generate code to automatically initialize every variable with a distinguished sentinel value. If at some point we find that a variable’s value is different from the sentinel, then that variable must have been initialized. If its value is the sentinel, we must double-check the flag. Describe a plausible allocation strategy for initialization flags, and show the assembly language sequences that would be required for dynamic checks, with and without the use of sentinels.