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C quiz questions

sovan chatt
Ranch Hand

Joined: Aug 09, 2010
Posts: 43
I need help with the following questions in
1)
output?
2)
I felt the answer would be 21,13,13,13 but the answer is 22,13,13,13.How b is coming as 22?
3)
I felt the answer should be 0, 1, 2, 3, 4, but is 0,0,1,2,3,4.How is the extra 0 coming?
4) why does 11 ^ 5 show 14
5)here a should have been 13(5*2+3) but it is coming as 25.How?
6)Why is this creating an infinite loop?
Mary Chellapa
Ranch Hand

Joined: Jul 26, 2011
Posts: 93
1. output = 10


Mary
Mary Chellapa
Ranch Hand

Joined: Jul 26, 2011
Posts: 93
wow i could answer only first ... and i thought i was good in C.
Stephan van Hulst
Bartender

Joined: Sep 20, 2010
Posts: 3989
    
  18

Note that most of the answers are actually undefined, because C doesn't have proper rules for order of evaluation.

That said, here are some explanations using left-to-right evaluation.

1.)
z = x++ - --y * b / a;
z = 5++ - --(-10) * 2 / 4;
z = 5 - (-11) * 2 / 4;
z = 5 - (-22) / 4;
z = 5 - (-5);
z = 10;


2.)
b = a++ + ++a;
b = 10 + 12; // a = 12;
b = 22;

printf("%d,%d,%d,%d", b, a++, a, ++a);
printf("%d,%d,%d,%d", 22, 12, 13, 14);


3.)
myFunc(5) -> myFunc(4); printf("%d, ", 4);
myFunc(4) -> myFunc(3); printf("%d, ", 3);
myFunc(3) -> myFunc(2); printf("%d, ", 2);
myFunc(2) -> myFunc(1); printf("%d, ", 1);
myFunc(1) -> myFunc(0); printf("%d, ", 0);
myFunc(0) -> printf("%d, ", 0);


4.)
^ is the binary XOR operator. The calculation goes like this:

00001011 // 11
00000101 // 5
________
00001110 // 11 xor 5 = 14


5.)
Assignment operators (including compound assignment, like *=) have lowest precedence. The calculation goes:

a *= 2+3;
a *= 5;
a = 5*5;
a = 25;


6.)
You get an infinite loop because you're never incrementing the loop variable i. You're passing i to the increment function by value. The function increments a copy of i, and leaves the original variable like it was. A working increment function would look like this:You would call it like this:


The mind is a strange and wonderful thing. I'm not sure that it will ever be able to figure itself out, everything else, maybe. From the atom to the universe, everything, except itself.
sovan chatt
Ranch Hand

Joined: Aug 09, 2010
Posts: 43
@Stephan van Hulst thanks for the explanations!.
I have got 1 more question.

if I insert 358 and 453 what will x and y hold?
Rob Spoor
Sheriff

Joined: Oct 27, 2005
Posts: 20080
    
  30

The correct answer to that is "try it yourself and find out".


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