CSCI 150, Spring 2003

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Solutions for Review sheet for 1st midterm

Practice Problems
The following problems are intended to help you study for the exam.

1)Given these boolean variables:
x = true, y = false, z = true

What is the value (true/false) of each of the following?

i)  x and (y or z)

Answer:	true

ii) (not x) or  (not(y and z))

Answer:	true

iii) y or (x and not z)

Answer:	false

2)Write a program that does the following:
Prompt the user to input a number.
Input the number from the keyboard
If the number is less than 100, write:
	XX is a low number.
where XX refers to the number inputted by the user.
Otherwise, write:
	XX is a high number.

	program lowOrHigh;
	var
		number : integer;
	begin
		writeln('Enter a number:');
		readln(number);
		if number < 100 then
		begin
			writeln(number, ' is a low number.');
		end
		else
		begin
			writeln(number, ' is a high number.');
		end;
	end.



3)  Compute the value of the following expressions:
a)  6 / 3 * 2

Answer: 4

b) (17 - 11) / 3 + 3

Answer: 5

c) Add parentheses to part b so that the addition is performed
before the division.

Answer: (17 - 11) / (3 + 3)

d) What is the value of c) ?

Answer: 1

4) a) What is the value of sum after the execution of the following code?

	sum := 0;
	for counter := 1 to 4 do
	begin
		sum := sum + 2 * counter;
	end;
	
Answer: 20
	

5) What is the output of the following code fragment (mySentence and partial are both strings)?

	mySentence := 'It was a dark and stormy night';
	partial := copy(mySentence, 8, 6);
	writeln(partial);

Answer: a dark

• a)

           program p1;
           var
             p2: integer
           begin
             p2 := 1;
           end.
           
   Answer: The semi-colon after the word integer is missing (on line 3).
  

  
  

• b)

           program s1;
                           var
           s2:             string;
                           begin
           s2 := '1';
           end.
           
  Answer: The indentation is inconsistent and confusing.
  

  
  

• c)

           program r1;
           begin
           if true then
              writeln('Truth is beauty.');
              end;
           end.
           
  Answer: The word begin is missing after the 'if true then' line (line 3).
  

  
  

• d)

           program t1;
           var
              circumference:  real;
              radius:         real;
           begin
              circumference := 3.14159265 radius * radius;
           end.
           
  Answer: The * is missing between 3.14159265 and radius.
  

7)  Consider the following while loop:
	sum := 0;
	count := 5;
	while count <= 10 do
	begin
		sum := sum + count;
		count := count + 1;
	end;

a) Fill in the following table for the values of count and sum each time through the loop (there may be more rows than you need in the table):

b)Write a for loop that does the equivalent of the above loop.

	sum := 0;
	for count := 5 to 10 do
	begin
			sum := sum + count;
	end;

  8. Consider the following pascal code:

     program z3;
     var
        sum,i: integer;
     begin
        sum := 0;
        for i :=1 to 4 do
           begin
              sum := sum + i;
           end;
        writeln(sum);
     end.
     

Answer: 10

  9. Fill in/write the necessary code for the following decision tree.

program catCheck (input, output);
var								
	answer : string; 				
begin						

	writeln('Do you have a cat?');
	readln(answer);
	if answer = 'yes' then
	begin
		writeln('What kind is it?');
		readln(answer);
		if answer = 'Siamese' then
		begin
			writeln('Good choice!');
		end
		else if answer = 'Tiger' then
		begin
			writeln('Another good choice.');
		end
		else if answer = 'Calico' then
		begin
			writeln('I have never had that kind.');
		end;
	end
	else
	begin
		writeln('You should get one.');
	end;
end.  {end of main program catCheck}

10. Fill in the necessary code to fill in the depositList array with deposit amounts entered by the user. You should keep track of the sum of all the deposits made, so that the print statement at the end of the program makes sense. You can assume there are exactly 1000 deposits made.

program deposit;
type
	realArray : array [1..1000] of real;
var
	loop   : integer;
	sum    : real;
	depositList : realArray;

begin
	sum := 0;

	for loop := 1 to 1000 do
	begin
		writeln('Enter deposit');
		readln(depositList[loop]);
		sum := sum + depositList[loop];
	end;


	writeln ('The sum of the deposits: $', sum:5:2);
end;