difference between i++ and ++i

i++ means 'tell me the value of i, then increment'

++i means 'increment i, then tell me the value'

For the prefix form:

• x is evaluated to produce the variable
• the value of the variable is copied to a temporary location
• the temporary value is incremented to produce a new value (not overwriting the temporary!)
• the new value is stored in the variable
• the result of the operation is the new value

For the post fix form:

• x is evaluated to produce the variable
• the value of the variable is copied to a temporary location
• the temporary value is incremented to produce a new value (not overwriting the temporary!)
• the new value is stored in the variable
• the result of the operation is the temporary copy

++i is definitely as fast as i++ but it may be faster.
The reason is the implementation.

In order to implement i++ the implementation needs to generate a temporary copy of i unlike the implementation for ++i.

But smart compilers can optimize the generate of this temporary, they certainly do for POD types