CS 2073, Computer Programming with Engineering Applications
Spring 1992
Final Examination
(10)1.	Suppose an array of integers has been declared

			A: array[1..100] of integer;

		Suppose the locations from 1 to N have values stored in them.  Write a code segment that 
will look up an integer X in this array.  The segment should set a variable K equal to the 
location of X in the array, or to 0 in case X does not occur in the array.

(10)	2.	Consider a user-defined (or enumerated) type, with corresponding declarations:

		 type colors = (red, blue, green, yellow, purple, black, white);
		 var color: colors;
	
		(a)  Is it legal to write 
			color := purple;
		 in a program?
		(b)  In case color has the value blue, what will ord(color) be equal to?
		(c)  In case color has the value blue, what will succ(color) be equal to?

(10)	3.	Write a segment of code that will evaluate the following expression:

			(h)[sin(a) + sin(a+h) + sin(a+2*h) + . . . + sin(a + (n-1)*h) + sin(a + n*h)],

		where  n = 100, a = 0, b = p, and h = (b-a)/n.  (Notice that a + n*h just equals b.)  In terms 
or calculus or areas or integrals, what does this sum represent?

(10)	4.	Give two of the more interesting facts about the C language that you learned from the 
lecture on C in class (or from class notes).  (For full credit you need something not 
completely trivial about C.)

(20)	5.	Suppose you have declarations like those for the Laplace programming assignment 
(Number 6):

const (* below, m's used for rows, n's for columns *)
      m1 = 20;  (* top of inner space at 212 degrees*)
      m2 = 40;  (* bottom of inner space at 212 degrees*)
      m3 = 60; (* lower boundary at 32 degrees *)
      m0 = 30;  (* start of liquid on the outside "bath" at 32 degrees*)
      n1 = 20;  (* left side of inner space at 212 degrees *)
      n2 = 40;  (* right side of inner space at 212 degrees *)
      n3 = 60; (* far right boundary *)
type atype = array[0..m3+1, 0..n3+1] of real;  (* rows and columns *)
     (* assumes that [0,0] is upper left corner *)
     ctype = array[0..m3+1, 0..n3+1] of char;  (* matching character array *)
var a: atype;
    c: ctype;

		(a)  Write a procedure initialize with one parameter of type ctype that will initialize 
all the characters of its parameter to blanks.  Does this parameter need to be a var (or 
reference) parameter?
		(b)  Write a procedure stars with two parameters, one of type atype and one of type 
ctype.  stars should store a star '*' in each position[i,j] of the c array in case the 
temperature in the corresponding position in the a array is greater than 100.

(20)	6.	Recall the random number generator random that we used in class.  In order to use it, you 
need the following declarations and initializations:
			var seed: double;
			function random(var seed:double): double;
			(* the rest of random here *)
			begin (* main program *)
			   seed := 474747.0; (* or any value from 1.0 to 2^31-1 *)
			   (* now make use of random *)
			end.
		(a)  Write a segment of code which will use this random number generator to print 100 
random real numbers between 0.0 and 1.0.
		(b)	Write a function DICE which will use this generator to simulate rolling two dice.  The 
function should return the integer representing the total number of spots rolled.  (A number 
between 2 and 12 inclusive.)
		(c)	Write a code segment which will keep track of the numbers of spots rolled, using 
an array declaration:

			var SPOTS: array[2..12] of integer;

		Each array element is a counter for that number of spots, so that if you get 5 from 
DICE, the array element SPOTS[5] should be incremented.  The segment should print 
out the counts after 1000 simulated rolls.  The output should look roughly like:

			SUM OF  1:   28
			SUM OF  2:   55
			   ...       ...
			SUM OF 12:   30
	
(20)	7.	Consider the following Pascal program that handles character strings of varying 
lengths:

program strings;
const Maxstr = 10;
type
   basicstring = array[1..Maxstr] of char;
   stringtype =
      record
         str: basicstring;
         len: integer
      end;
var r, s, t: stringtype;
    n, k: integer;

procedure readstring(var s: stringtype);
var ch: char;
    i: integer;
begin
   i := 0;
   while not eoln and (i < Maxstr) do
   begin
      i := i + 1;
      read(ch);
      s.str[i] := ch
   end;
   s.len := i;
   readln
end;

procedure writestring(s: stringtype);
var i: integer;
begin
   write('"');
   for i := 1 to s.len do
      write(s.str[i]);
   writeln('"')
end;

function length(s: stringtype): integer;
begin
(* the code for this function goes here *)
end;

procedure substring(s: stringtype;
     n: integer; k: integer; var t: stringtype);
var i: integer;
begin
   if (n + k - 1 > s.len) or (n <= 0) then
      writeln('*** error in substring ***')
   else
   begin
      for i := 1 to k do
         t.str[i] := s.str[i + n - 1];
      t.len := k
   end
end;

procedure substring(r, s: stringtype; var t: stringtype);
begin
(* the code for this procedure goes here *)
end;

begin (* main program *)
   writeln('Please enter a string on one line');
   readstring(r);
   writestring(r);                  (* question (c) *)
   writeln('Length:',length(r));     (* question (c) *)
   writeln('Enter a starting position for a substring');
   readln(n);
   writeln('Enter a length for a substring');
   readln(k);
   substring(r, n, k, t);
   writestring(t);                   (* question (d) *)
   writeln('Length:', length(t));    (* question (d) *)
   writeln('Please enter a second string on one line');
   readstring(s);
   concat(r, s, t);
   writestring(t)
end. 
 
		(a)  Which of the two basic methods for representing varying length strings are 
employed here?  (Special character at the end, or store the length explicitly?)
		(b)  Fill in the code for the function length above, so that it will correctly return the 
length of a string.
		(c)  Suppose you type in "wagner" followed by a return in response to the "Please 
enter a string on one line" message.  Exactly what will be stored in the 
global record structure named r?  What will be printed out by the writestring and 
the following writeln?  (These are marked as "question (c)" above.)
		(d)  Suppose you enter 3 for a starting position (the value of n) and 2 for a length (the 
value of k).  After the call to substring, what will be printed out by the 
writestring and the following writeln? (These are marked as "question 
(d)" above.)
		(e)  The concat procedure should just tack r and s together to form a new long string 
named t.  Give the code for this procedure.