Computer Science : Boolean
Study concepts, example questions & explanations for Computer Science
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Example Questions
Example Question #1 : Boolean
int j=6;
int k=0;
int l=2;
int c = (j|k) & l;
What is the value of c?
6
4
0
2
1
2
The parenthesis indicate which operations need to be completed first. J or'd with k gives an answer of 6. Remember that these boolean operations are done by using the binary representtion of the numbers. 6 in binary is 110 and 0 in binary is 000. 6 anded with 2 is 2.
Example Question #2 : Boolean
Consider the code below:
int[] vals = {841,-14,1,41,49,149,14,148,14};
boolean[] bools = new boolean[vals.length];
for(int i = 0; i < vals.length; i++) {
bools[i] = vals[i] > 20 && vals[i] % 2 == 0;
}
for(int i = 0; i < bools.length; i++) {
if(bools[i]) {
System.out.println(vals[i]);
}
}
What is the output of the code above?
true
false
false
true
false
true
false
true
false
No output
841
41
49
149
false
false
false
false
false
false
false
true
false
148
148
This code uses a pair of parallel arrays, one being a boolean containing the result of the logic
vals[i] > 20 && vals[i] % 2 == 0
as applied to each element in the vals array.
The logic will evaluate to true when a given value is greater than 20 and also is even. (Remember that the % is the modulus operator, giving you the remainder of the division by 2 in this case. When this is 0, the division is an even division without remainder. When the divisor is 2, this means the number is divisible by 2—it is even.)
Now, in the second loop, it merely prints the values for which this was true. (This isn't the most efficient algorithm in the world. It is merely trying to test your ability to use parallel arrays and boolean values!) There is only one number in the entire list that fits: 148. Notice, however, that it does not output the boolean values. Those answers are traps that are trying to see if you are not paying attention.
Example Question #2 : Boolean
In the following equation, considering the boolean variables x, y, and z, which of the following combinations of values will evaluate to true?
(x\,\&\&\,!y)\,||\,((!x\,||\,z)\,\&\&\,!(y\,||\,z))
x == false, y == false, z == true
x == true, y == false, z == false
None of the answers evaluates to true.
x == false, y == true, z == false
x == true, y == true, z == true
x == true, y == false, z == false
When evaluated with x == true, y == false, z == false, the equation comes out to be
All other combinations of values produce false.
Example Question #21 : Standard Data Structures
#include <iostream>
using namespace std;
bool bigger(int x, int y)
{
if (x>y)
return true;
else
return false;
}
int main()
{
bool test;
test!=bigger(10,7);
cout<<test;
}
What will be the value of test after the previous code is run?
0
false
10
true
7
0
The function "bigger" defined before main returns a value of type bool and takes in two integer inputs. It compares the first value to the second. If it it greater, it returns true. Otherwise, it returns false. In main, a new variable test is called, and it is of type bool as well. This automatically eliminates 3 out of the 5 possibilities.
"test" is defined as the opposite of the outcome of the bigger function with the two inputs are 10 and 7. 10 is bigger than 7, so the function returns true. Since test is the opposite of that, it is false.
Example Question #3 : Boolean
Convert the decimal number 67 to binary.
1000010
1100011
1000101
1000011
1001010
1000011
In a regular number system, also known as decimal, the position furtherest to the right is 
Explanation
1000011 The bolded number has a value of 1
1000011 The bolded number has a value of 2
1000011 The bolded number has a value of 64
The positions that are marked true (as 1) in the binary number 1000011 corresponds to the numbers 64, 2, and 1 which added up equals 67
Step By Step
- To convert the number 67 to binary, first find the digit place number that has the largest number possible that is less than or equal to 67. In this case it would be the position holding
.
- The number for 64 is 1000000
- To get 67, we need to add 3
- Again, find the digit place number that has the largest number possible less than or equal to 3. In this case, it would be
- The number for 66 (64 + 2) is 1000010
- To get from 66 to 67, repeat the steps from before.
- The number for 67 (66 + 1) is 1000011
Example Question #21 : Primitive Data Types
In Swift (iOS), define an unwrapped boolean.
var variable
variable: Bool
var variable: Bool
variable: Boolean
var variable: Bool
In Swift, every variable must be declared with var before the name of the variable. This automatically knocks out two of the answers. After we eliminate those two, we see var variable and var variable: Bool. var variable would be a correct answer if the prompt had not asked for an unwrapped boolean. var variable: Bool performs the unwrapping by declaring the variable to be a boolean specifically.
Example Question #22 : Primitive Data Types
How do we set a method to return a Boolean in Swift(iOS)?
func method -> Bool {}
func method() -> Bool {}
method() -> Bool {}
method() -> Bool {}
func method() -> Bool {}
func method() -> Bool {}
In Swift, all methods must first say what they are. They are functions, so they are prefixed with func. Next, methods must have a name. In this case, we named it method. All methods need to specify parameters, even if there are no parameters. So, method() i.e. no parameters. Finally, we wanted to return a boolean. So we set the return type using -> Bool.
Example Question #22 : Primitive Data Types
How do we set a method to return a Boolean in Swift(iOS)?
func method -> Bool {}
func method() -> Bool {}
method() -> Bool {}
method() -> Bool {}
func method() -> Bool {}
func method() -> Bool {}
In Swift, all methods must first say what they are. They are functions, so they are prefixed with func. Next, methods must have a name. In this case, we named it method. All methods need to specify parameters, even if there are no parameters. So, method() i.e. no parameters. Finally, we wanted to return a boolean. So we set the return type using -> Bool.
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