Comparing the post increment and pre increment operators in C Programming

[Hebrew]

Please tell me which amongst the pre increment operator and the post increment operator is faster in C programming or both of them are equally fast ? please try to explain me the reason behind it as I am preparing to give an Interview in a software Company and it is one of the common question being asked by the interviewer ?

[Zecho]

According to my Knowledge the pre increment operator is much more efficient and faster than the post increment operator. since, the post increment operator object increments itself and after that it returns a temporary object containing its old value. This is true for even built in data types. Due to this reason the pre increment operator is faster than the post increment operator.

[absolute55]

Both the post increment and pre increment operators doesn't have much difference in timing. Although if we use pre increment in a for loop it proves to be quite faster. In both the operations the operand is incremented. But, the post increment operator firsts make a copy of the old value and then increment and returns the old value. Whereas the pre increment operator just increments and simply returns the value.

[Reegan]

To explain this I would like to give you a short Example

i=5; the value of i is 5 on this line
i++; the value of i=5 on this line
++i; the value of i is 7 on this line

from the above example we can easily understand that pre increment operator increments the value of i on the line itself whereas, the post increment operator increments the value of i on the second line.

[opaper]

Every time when the post increment operator is used it performs two tasks firstly it stores the value of the variable in temporary location suppose in any of the register and then it increments the value of the variable and save it to the memory location. The incremented value is then transferred from the register to wherever it was assigned. Apart from that the pre increment does not have to transfer the value That's why it is quite faster than the post increment operator

[MindSpace]

We cannot say it for sure since all that depends on the target processors. let us consider a few processors
1.Sun's SPARC processor: This processor always executes that instructions that follows a conditional branch, without taking care of the condition inside the branch.
2.GCC code generator:This hides the increment statement which helps in speeding of the post increment instruction.
So, Its quite obvious that different processor implements different tricks for executing an increment statement faster than the other statement.

[jeryruse]

Hello Hebrew.
They both increment the variable. But the value returned by the pre-increment operator is the value of the variable after it has been incremented, while the value returned by the post-increment operator is the value before it has been incremented.
For example:
int a = 1;
int b = ++a;
// Now a is 2 and b is also 2.

int a = 1;
int b = a++;
// Now a is 2 but b is 1.
Thanks for sharing it.