(a) Develop stack machine code equivalents of the following simple programs:
(1) void main () { // print numbers 0 through 10
for (int i = 0; i <= 10; i++) write(i, "\n")
}
(2) void main () { // demonstrate hailstone series
int m;
read("what is the first term of the series? ", m);
write(m);
int n = 1;
while (m != 1) {
if (m % 2 == 0) m = m / 2;
else m = 3 * m + 1;
n = n + 1;
write(m);
}
write("\n", n , " terms in that sequence");
}
(b) The following code is supposed to check to see whether the elements of an array form a non-decreasing sequence. Does it do so correctly? If not, how would you fix it, and what would the resulting PVM code look like?
void main () {
// check to see whether an array has elements in ascending order
const size = 20;
int[] list = new int[size];
list[5] = -1;
int i = 0;
bool inOrder;
while (i < size) {
if (list[i] > list[i+1])
inOrder = false;
else
inOrder = true;
i = i + 1;
}
write(inOrder);
}
(c) Consider the following general form of T diagram. Although it uses the letters A through I in the various arms of the Ts, one could draw the diagram with fewer letters. How and why?
.--------------------------. .--------------------------.
| | | |
| A ----------> B | | C -----------> D |
| | | |
`-------. .--------------------------. .-------'
| | | |
| E | F --------> G | H |
| | | |
`------------------. .------------------'
| |
| I |
| |
`----------'
(d) In the practical sessions you should have used the Extacy Modula-2 to C translator. This was developed in Russia by a team who used the JPI Modula-2 compiler available for the PC. But the demonstration system we downloaded from the Internet came with the file XC.EXE, and a few other modules written in Modula- 2 (but not the source of the XC.EXE executable itself). Draw T-diagrams showing the process the Russians must have used to produce this system, and go on to draw T-diagrams showing how you managed to take the program SIEVE.MOD and run it on the PC using the Borland C++ system as your compiler of choice.