# Output of C programs | Set 56 (While loop)

Prerequisite : While loops
Q.1 What is the output of this program?

 `#include ` `using` `namespace` `std; ` `int` `main() ` `{ ` `    ``unsigned ``int` `x = 3; ` `    ``while` `(x-- >= 0) { ` `        ``printf``(``"%d  "``, x); ` `    ``} ` `    ``return` `0; ` `} `

Option
a) 3 2 1 0
b) 2 1 0 -1
c) infinite loop
d) -65535

`Answer : C`

Explanation: Here x is an unsigned integer andit can never become negative. So the expression x–>=0 will always be true, so its a infinite loop.

Q.2 What is the output of this program?

 `#include ` `using` `namespace` `std; ` `int` `main() ` `{ ` `    ``int` `x = 3, k; ` `    ``while` `(x-- >= 0) { ` `        ``printf``(``"%d  "``, x); ` `    ``} ` `    ``return` `0; ` `} `

option:- a
a) 3 2 1 0
b) 2 1 0 -1
c) infinite loop
d) -65535

`Answer: b `

Explanation: Here x is an integer with value 3. Loop runs till x>=0 ; 2, 1, 0 will be printed and after x>=0, condition becomes true again and print -1 after false.

Q.3 What is the output of this program?

 `#include ` `using` `namespace` `std; ` `int` `main() ` `{ ` `    ``int` `x = 0, k; ` `    ``while` `(+(+x--) != 0) { ` `        ``x++; ` `    ``} ` `    ``printf``(``"%d  "``, x); ` `    ``return` `0; ` `} `

option
a) 1
b) 0
c) -1
d) infinite

`Answer : C `

Explanation Unary + is the only dummy operator in c++. So it has no effect on the expression.

Q.4 What is the output of this program?

 `#include ` `using` `namespace` `std; ` `int` `main() ` `{ ` `    ``int` `x = -10; ` `    ``while` `(x++ != 0) ` `        ``; ` `    ``printf``(``"%d  "``, x); ` `    ``return` `0; ` `} `

option
a) 0
b) 1
c) -1
d) infinite

`Answer: b `

Explanation: The semicolon is after the while loop. while the value of x become 0, it comes out of while loop. Due to post-increment on x the value of x while printing becomes 1.

Q.5 What is the output of this program?

 `#include ` `using` `namespace` `std; ` `int` `main() ` `{ ` `    ``while` `(1) { ` `        ``if` `(``printf``(``"%d"``, ``printf``(``"%d"``))) ` `            ``break``; ` `        ``else` `            ``continue``; ` `    ``} ` `    ``return` `0; ` `} `

option
a) Garbage value
b) 1
c) 0
d) Error

`Answer : a `

Explanation: The inner printf executes and print some garbage value.

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