Hi kungfu,
Consider a,b,c variables
1) a=b;
b=c;
c=a;
2) a <=b;
b<=c;
c<=a;
case 1 outputs: a---value of b.
b---value of c.
c---value of a.
case 2 outputs: a----value of b or c
b----value of a or c
c----value of b or a
In the first case, the simulator assigns sequentially. One after the other same as C language.
In the second case, the simulator treats the statements concurrently.
Internally all the concurrent statements are compiled sequentially with some min. delay known as delta delay.
We dont know which statement in the second may be executed first. It could be statement1 or 3 or could be 2.
I hope its clear
Thanks and Regards
Deepak