Hello Vijay (Sorry for the late arrival)
To answer your question.
1. The PC
has revolutionized the world more than any other machine in modern times
2. The PC
has revolutionized the world more than has any other machine in modern times
-- the first one correctly implies that the PC (we know it is a machine) has revolutnz the world more than other machine. Here the HAS is understood. HAS is understood to have been placed after ANY OTHER MACHINE. Hence the sentence can be understood as
1. The PC has revolutionized the world more than any other machine
has in modern times. But we do not have to use the HAS. Since it is comparing machine to a machine.
Let me give an example.
Polio has created more fear than any other disease, in olden days. Correctly compares DISEASE to DISEASE. If I re-write the sentence with HAS... we can get the jist of what I mean.
Polio has created more fear than
has any other disease. The inclusion of HAS is unneccessary. Look at the below sentence where HAS is to be used.
Compare both !!!
Polio vaccine has a greater effect in treating polio patients than it
has on other patients.
Polio vaccine has a greater effect in treating polio patients than other patients.
Here, without the HAS, it sounds like we are comparing polio vaccine with patients. Hence, when comparing like terms, HAS is not required. A Tip from my side is, when you see an additional noun, be aware, that the sentence is trying is create a confusion on the comparision between the original and the new noun.
I hope this helped.