CMPT/ISYS 140 Fall2005 FINAL ch1-7 Part2, Trinity Western University. 27 Oct 2005.

Name:	__________________
Student ID:	__________________

Explain all the differences between assignment
compatibility and expression compatibility.
Give examples.
Explain all the differences between the built-in string concatenation operator (+) and the standard library function Strings.Concat().
Explain the advantages and disadvantages of FOR versus WHILE.
Be specific (not just "one is more flexible").

The following module will not compile. What is wrong? How would you fix it?

MODULE BuggyReadVector;
	(* user inputs values to initialize a vector *)
FROM SWholeIO IMPORT
	ReadCard;
VAR
	myVector : ARRAY [1 .. 11] OF CARDINAL;
	count, counter : CARDINAL;
BEGIN
	FOR count := 1 TO 10
		DO
			counter := count;
			ReadCard (count);
			SkipLine;
			myVector [counter] := count;
		END;
	myVector [counter + 1] := 11;
END BuggyReadVector.

In the remainder of this exam, you will be writing up a library and test-suite for generating pseudorandom numbers: Your library should provide a Random() function, which returns a new random real between 0 and 1 each time it is invoked. There should also be a way to seed the random number generator. The default seed (if the user does not manually set it) should be 0.
1. Write a complete Modula-2 DEFINITION file for your library (call it PseudoRandom). In comments after each procedure declaration, define brief preconditions and postconditions for that procedure.
2. Write a brief user manual for your PseudoRandom library. Your target audience is a fellow Modula-2 programmer who doesn't know how your library works, but wants to use it in his/her own program. Include a short abstract at the beginning of the user manual: one or two sentences summarizing the purpose of this library. Include a couple examples of how to use your library.
3. Write pseudocode for each procedure in your library. You may wish to design additional helper functions for internal use within your library, as appropriate; if you do, then write pseudocode for them, too.
4. List all libraries and library items you need to import.
5. List any variables (and their types) you will declare in the scope of the library implementation module. Also, for each procedure in your library (including helper functions), list any variables (and their types) local to that procedure.
6. Write a complete Modula-2 IMPLEMENTATION file for your library.
7. Write a separate test suite (test harness, test framework) for your library -- a complete Modula-2 program module that imports from your library. This program should produce 1,000 random CARDINALS between 0 and 9,999 and save them into a file of the user's choosing. The numbers should be formatted ten per row, in columns: e.g.,
```
	9472 3930 4876  239 1029   12 7349 1920    0 2382
	3390 1528    3 5867 9999 8821 2002   77 1103  902
	....
```
Notes:
- Although your pseudorandom number generator won't be "truly" random, you should take reasonable efforts to make it not trivial.
- You may use LONGREALs if you wish, but you are not required to.
- Write your answers on a separate sheet of paper. You may wish to write rough drafts and/or sketch your design ideas on a separate sheet of paper. This is fine (and might even help with partial credit), but just make sure you have a clean, neatly written final version of each part of the question, clearly indicating which part of the problem it answers.
- Please try to indent and format your code properly so it can be read easily. Unless otherwise specified, comments within your code are not required on this exam, however if your code is incorrect, your comments may earn you partial credit if they show good design thinking. Little partial credit will be given for uncommented incorrect code.
- If you are short on time, prioritize getting the design and main ideas right and don't worry as much about the details of syntax. Forgetting a semicolon or misspelling IMPELLEMANETATATION is not a big deal.