# Introduction to C programming/Quizes/BooleanLogic/Answers

Jump to navigation
Jump to search

## Question 1[edit | edit source]

Assume that w=6, x=10, y=6 and z=3. What are the truth values of the following statements?

- w<9
- True. 6<9

- w!=y
- False. 6 is equal to 6

- z>x
- False. 3 is less than 10

- z<=y
- True. 3 is less than 6

- x-6>y*2
- False. x-6 is 4. y*2 is 12. 4 is less than 12, not greater.

## Question 2[edit | edit source]

With the same values of w,x,y and z, what are the values of the following combinations?

- w<9 && w!=y
- False. w<9 is true, but w!=y is false. If either term of an AND is false, the total is false.

- x+7>2 || x==6
- True. x+7>2 is true. x==6 is false. If either part of an OR is true, the total is true. In fact, the compiler won't even check the second term, it already knows the total is true.

- !(x-9>1)
- True. x-9>1 is false (its equal). The NOT of a false statement is true.

- !((x>y) && (x<z))
- True. x>y is true. x<z is false. So their AND is false. And the NOT of a fasle statement is true.

- (x>7) && !(x>7)
- False. x>7 is true. !(x>7) is false. If either part of an AND is false, the total is false. This is actually a trick question- x && !x is always false.

- (x>7) || !(x>7)
- True. x>7 is true. !(x>7) is false. If either part of an OR is true, the total is true. This is another trick question- x || !x is always true.

## Question 3[edit | edit source]

Under what values of x, y, and z do the following numbered statements get executed? Give the answers in forms like x>y>z.

if(x==y){ statement 1; statement 2; } else if(y>z){ statement 3; if(x==z){ statement 4; if(y<z){ statement 5; } } } else{ statment 6; }

- statement 1: this occurs only if x==y. We get this from the if its in
- statement 2: this occurs only if x==y. Since it is in the same block as 1, it has the same conditions
- statement 3: this occurs only if x!=y and y>z. We get the first term due to it being in an else branch for if 1, and the second from the second if
- statement 4: this occurs only if x!=y, y>z and z==x. We get this from the 3 ifs/elses it's in.
- statement 5: never. This statement would require y>z and y<z. This cannot be true, so the line never executes. A compiler may warn you of this.
- statement 6: this occurs only if x!=y and y<=z. We get this as the else from the 2 above ifs.

## Question 4[edit | edit source]

Under what values of x do the following numbered statements get executed?

switch (x){ case 0: statement 1; break; case 1: statement 2; case 2: statement 3; case 4: statement 4; break; case 5: case 6: statement 5; default: statement 6; break; }

- statement 1: only if x=0
- statement 2: only if x=1
- statement 3: only if x=1 or x=2 (no break after statement 2, so a 1 would fall through)
- statement 4: only if x=1, x=2, or x=4. No breaks for either case 1 or 2.
- statement 5: only if x=5 or x=6.
- statement 6: any value of x except 0,1,2, and 4. Notice that it does happen for 5 and 6 due to not having a break.