Part 3, Selection

Question 1

what is a Boolean comparison

Answer 1

a Boolean comparison compares two values and reports/returns back either true or false

Question 2

name three Boolean comparisons

Answer 2

1. is equal to
2. is less than
3. is greater than

Question 3

what is a compound condition

Answer 3

a compound condition is a condition which compares two or more separate conditions

then reports back true or false depending on the outcome of those individual conditions and the type of compound condition being used

Question 4

name three types of compound conditions

Answer 4

1. and ( {condition 1} and {condition 2} )
2. or ( {condition 1} or {condition 2} )
3. not ( not{condition 2} )

Question 5

you have used an “or” compound condition

what might you need to do in the following block of code

Answer 5

in this case we may need additional checks to find out which component of the compound condition was true

Question 6

explain what a “mutually exclusive condition” is

Answer 6

a mutually exclusive condition is where only one outcome can ever be true out of a given set of events

example
3 = 3
so cannot be
3 < 3
or 
3 > 3

Question 7

what is “sequential selection”

Answer 7

sequential selection is having a list of selections one after the other

example
if (x) {
    do y
}
if (x) {
    do y
}
if (x) {
    do y
}

Question 8

what is “nested selection”

Answer 8

nested selection is where you have a selection within a selection

example:
if (x) {
    do y
    if (x) {
        do y
    }
}

nested selections will not run if there there parents condition did not allow the selections code to run

Question 9

in what situation would nested selection be more efficient than sequential selection

Answer 9

when there is a case of a mutually exclusive condition then a nested selection would be more efficient

this is because only one of the selections can be true meaning a nested selection would make no further checks but a sequential selection would check anyway wasting resources

Question 10

what four reasons are “flag variables” or “flags” used for

Answer 10

a flag variable is a variable that can be used to check if

1. an event has taken place
2. a condition was met
3. having an event confirmed without having to make checks again later in the code
4. checking an event did take place which can no longer be checked

Question 11

what two states will a flag variable have

Answer 11

1. true

2. false

Question 12

you see words such as “if”, “otherwise”, “depends”, “either”, “decide” in the specification

what do these words suggest you will need inside your program

Answer 12

words such as “if”, “otherwise”, “depends”, “either”, “decide” and any synonymous suggest that selection will be needed within your program

Question 13

can you think of five words that suggest selection may be needed in your algorithm and program

Answer 13

1. “if”
2. “otherwise”,
3. “depends”,
4. “either”,
5. “decide”

Question 14

what is a “boundary value”

Answer 14

a boundary value is a value that determines when the program should behave differently

example:
if (x = 5) {
do something
}

here 5 is the boundary value

Question 15

what is “boundary testing”

Answer 15

boundary testing involves testing any boundary values that might exist

Question 16

when boundary testing what three tests should be carried out

Answer 16

1. test one value lower than the boundary value
2. test the boundary value
3. test one value higher than the boundary value

Question 17

why is boundary testing performed

Answer 17

the reason for boundary testing is to ensure that the expected code is ran for the boundary value and its surrounding values