c programming

Question

what is the o/p
 

#include<stdio.h>
void main()
    {
    int a=5;
    printf("%d   %d   %d",a++,++a,--a);
    }

also suggest me notes so i can clear my concept about printf function (For Gate)

Comments

Don't you have all previous year GATE questions with you? Any such question asked in GATE ever? Any question even related to printf?

---

o/p:5,7,6

Printf is a function here we are calling printf function and passing 4 argmnts.

() has left to right associativity.

If we pass function arg. as an expression then first it evaluate after that it pass the value to calling function.

2nd arg: as a++ is post-Increment operation so first it pass the value 5 then increase to 6.o/p:5

3rd arg: as ++a is pre-Increment operation so first it increment the value to 7 then it pass to it. o/p:7

4th arg :same as 3rd arg.o/p:6

---

sir i have seen many questions but still i have not found any generalized theory so i can give all answer correct without remembering  questions  that why i was asking about source

---

"I have seen many questions"

From where?

Answer 1

According to C standard, the answer is undefined as "Between the previous and next sequence point an object shall have its stored value modified at most once by the evaluation of an expression. Furthermore, the prior value shall be accessed only to determine the value to be stored."   

To know more read this explanation : https://www.quora.com/What-does-an-expression-involving-multiple-post-pre-decrement-increment-operators-evaluate-to-in-C-and-C++

Answer 2

it is undefined in c standard .

please c , @arjun sir's explanation 

https://gateoverflow.in/62411/undefined-behaviour-in-c

Comments

Thanks

Answer 3

The result is dependent on the compiler as wether the expression should be evaluated from left-to-right or right-to- left is not defined anywhere . Different compiler use to evaluate the given expression in different way.

 

This is an ambiguous question and will not be asked in GATE for sure.

Answer 4

it will print 5,6,6

Comments

how ?

which rules follow by printf function ?

Answer 5

In your question there are following operator are used..
Post increment operator:-.  eg...a++ (aplusplus)that means it first use the value then after increase it by 1and use it..so a=5
So,*******""first output is 5
Pre increment operator:- eg.++a (plusplus a) that means it first increase the value by 1 and after then use..above a store the value 6 then
So,******""second output is 7
Pre decrement operator:- eg.--a(minus minus a) that means it first decrease the value by 1 and after then use.above a store 7
Then
So,******""Third output is 6

Answer 6

o/p is: 5  5  4