hi...
SRA performs the signed division .
it can be explained as follows.
As we know shifting a bit to left by 1-position is equivalent to multiplication by 2.
similarly, shifting right by 1-bit performs division operation.....
Now about retaining the sign....
In shift right arithmetic operation the lsb will get a new bit from 1st bit and continues... but the msb will be retained...
so SAR performs the signed arithmetic operation...