Additioanl notes on comparisons

We have seen how to compare numbers, like x<=3, z>x+y. We can use the larger-than, >, and smaller-than, <, in order to compare strings. The comparison is done by alphabetical order.

Follow these examples in order to answer the questions below.

• The condition ("anaconda" < "elephant") evaluates to TRUE. The comparison is donde letter by letter starting on the left. As 'a' comes first than 'e' in the alphabet, the expression evaluates to TRUE.
• Given x='John' and y='Peter', the condition (x>y) evaluates to FALSE: 'J' comes before 'P', not after, so it is x<y, and that condition is false.
• Given x='abracadabra' and y='abraca', we get the following truth values:
  • (x<y) is FALSE
  • (x>y) is TRUE
  • (x==y) is FALSE
  x shares the same starting string with y, but the latter is shorter. Hence it is considered "smaller", or that it comes first than x.

Questions (K|C|A)

Write your answer in the corresponding textboxes or choose the rigth radio buttons/checkboxes.

1. What will be shown by the following code fragment

   
   var x = 2 ;
   var y = 2 ;
   if ( x > y ) { 
   	alert("True") ;
   }
   else {
   	alert("False") ;
   }
   
   					

   True
   False
   None
   Will print an error message
2. What will be shown by the following code fragment

   
   var x = "Monday" ;
   var y = "Monday" ;
   if ( x == y ) {
   	alert("True") ;
   } else {
   	alert("False") ;
   }
   
   					

   True
   False
   None
   Will print an error message
3. What will be shown by the following code fragment

   					
   						var x = 2 ;
   						if ( x == 2 ) {
   							alert("True") ;
   						}
   					
   					

   True
   False
   Nothing
   Will print an error message
4. What will be shown by the following code fragment

   
   var x = 3 ;
   if ( x == 2 ) {
   	alert("True") ;
   }
   
   					

   True
   False
   Nothing
   Will print an error message
5. Enter the value that will be shown by the following code fragment.

   
   x = 3 ; 
   y = 10 ;
   if (x > 0){
      y = 12;
   }
   y = y + 5 ;
   alert(y) ;
   
   						

6. Enter the value that will be shown by the following code fragment.

   
   x = -3 ;
   y = 10 ;
   if (x > 0){
      y = 12 ;
   }
   y = y + 5 ;
   alert(y) ;
   
   						

7. Enter the value that will be shown by the following code fragment.

   
   x = -3 ;
   y = 10 ; 
   if ( x > 0 ) {
      y = 12 ;
      y = y + 5 ;
   }
   alert(y) ;
   
   						

8. Select the values of x for which the following code will produce the value "yes". There may be more than one correct choice.

   
   if ( ! (x < 5) ) {
    alert("yes") ;
   }
   else {
    alert("No") ;
   }
   
   						

   3
   5
   10
   50
9. Select the values of x for which the following code will produce the value "No". There may be more than one correct choice.

   
   						function choose(x){
   							if ( x < 5) || x > 90) {
   							 return "yes";
   							}
   							else {
   							 return "No" ;
   							}
   						}
   						alert( choose(y) ) ;
   						
   						

   3
   5
   10
   100
10. what name will this code show?

    
    var name1 = "John" ;
    var name2 = "Donald" ;
    var x = 30 ;
    var person = "unknown"; 
    
    if ( name1 < name2 ) {
     person = name1 ;
    }
    else {
     person = name2 ;
    }
    alert( person ) ;
    
    						

    John
    Donald
    unknown
    x
11. what name will this code show?

    
    var name1 = "John" ;
    var name2 = "Donald" ;
    var x = 30 ;
    var person = "unknown"; 
    
    if ( name1 < name2 ) {
     person = name1 ;
    }
    else if (x > name2) {
     person = name2 ;
    }
    alert( person ) ;
    
    						

    John
    Donald
    unknown
    x

Programming in JavaScript

Note: Make sure to resize the text boxes so that they completely show your answers.

1. Write a program that calculates the following sum: 1+2+3+...+137 using a while loop. Also, write as a comment the answer you get. //sum is
2. Write a program that calculates the following sum using a while loop:
   -2-1+1+2+3+4+5+6+7+8+9+10
   Note: you cannot just assign this expression or print it as it is. Also, write as a comment the answer you get. //sum is
3. Write a program that calculates the following sum: 0 + 2⁰+ 2*2¹+ 3*2²+ 4*2³+ 5*2⁴+ 6*2⁵. Also, write as a comment the answer you get. //sum is
4. Write a program that calculates the following product: 1*2*1/3*4*1/5*6*1/7*...*1/19*20. Also, write as a comment the answer you get. Notice: You must use only one while-loop. Yet there are different ways to solve this problem. //product is
5. Somebody scrambled our code. Reorder the different lines of code shown here so that you end up with a program that shows in order the following messages: "Happy birthday to you" (twice), "Happy birthday dear Julia", "Happy birthday to you". Notice: You cannot remove nor add anything and all text below must be used in the final program i = i + 1 alert("Happy birthday dear Julia") ; while ( i<=2 ){ } alert("Happy birthday to you") ; i = 1 alert("Happy birthday to you") ;
6. Write a program that prompts the user to guess a number. If it is correct, show a dialog (alert) window with the message "Correct!". If the guess is not right, show a dialog box with the message "Sorry. Incorrect guess.". You have to choose the hidden number yourself and store it in a variable called x.
7. Write a program that asks the user for a number, it assigns it to a variable called N, and then calculates the following sum: 1+2+3+...+N. Also, write as a comment the answer you get when the user inputs 137. //sum is
8. Write a program that prompts the user to guess a number. This time we will give the user 3 posibilities to guess it right. At any time, if the guess is correct, show a dialog window saying so. If a guess is larger than the hidden number the program must show a dialog box saying "It's smaller!"; if a guess is smaller than the right number, the program must print "It's larger!". If after the third try the guess is not right, show a dialog box with the message "Game over.". You have to choose the hidden number yourself.