Answer: The idea behind this recitation: Start with a sequence of straight-line code inside a main function, with no functions or function calls, no loop constructs, no structured if-then-else, but only using gotos, ifs with a goto as target, and so forth, to carry out a computation. Even the "mystery" program is a fairly simple example that will cause students a lot of grief (sorry!).

The first method of translation (using a single while and a single switch, or a single while and a single extended if-the-else) shows that such a program can always be rewritten without gotos. This is mostly of theoretical interest, because the gotoless program is even more complex than the original. You talk about a double while loop, but a double loop is implicit in the original code with gotos.

Clearly, recovering the original stuctured form (if there was such an original stuctured form) would be preferable, but in general this cannot be done. Just defining this problem (what might "the original structured form" mean?) seems difficult or impossible. The "mystery" program shows that even for a simple example (one that did come from a well-structured original program) it can be difficult to recover anything like the original.

Restating: When you are faced with a program with gotos, and you don't want or can't have the gotos, you have two basic choices:

1. You can always use a while and switch to simulate execution of the original program, but this doesn't make a fundamental change and is no help in understanding the original program.
2. You can try to recover the original loops and other structures. You will not always be able to do that.

Answer: The hint that goes along with item 7 in the recitation is a pretty big hint. First identify simple (small) loops that you can find, while eliminating some labels and gotos. Make sure you keep compiling and running the code (because you will inevitably make mistakes), and finally be aware that the code you see comes from an original program that had a function call and the body of that function. This is a pretty tough exercise.

Answer: To answer the last question first, yes, everything should be concatenated into one big text file (be sure to save it as "text"), and the result submitted. Please arrange things in the order given and number them as in the recitation.

First, you should have the two programms, rewritten with a single while and a single switch, and with no gotos or labels. Each of these programs should be followed by the result of a run.

Next, you should have the same two programs, rewritten so as to recover the original form (if possible), that includes loops and if-the-else's. No labels, no gotos, no switch statements. Again include the output of each program. The first program is relatively simple (just a loop within a loop), while the second program is quite hard. (You shouldn't invest too much time in it.)

Answer:I should have left these off. These are examples of illegal floating point constants. The compiler will flail away at them in different ways, but there will always be an error message.