Ubuntu :: Measuring The Time Of A Code?

I am a beginner to C and C++ and so far I have learned two ways to measure the time my program takes to run.

Method 1: Just compile your C file and if the executable is say a.out just type time ./a.out

Method 2: Here the general structure of the code is

Code:
#include<stdio.h>
#include<time.h>
int main(void)

[Code]....

Question 1 Do Method 1 and Method 2 return the same times?

Question 2 Method 1 gives three times real, usr and sys . Is it true that USR+SYS= TIME GIVEN BY METHOD 2

I have performed some experiments with small codes which return the squares of numbers uptill 36000 and I feel the answer to question 2 is yes