IGNOU marking system

Will you please help me by providing the information about the marking system in IGNOU? Also tell me what's meant by A, B, C, D?

[Quick Sam]

IGNOU is Indira Gandhi National Open University. It is a distance learning national university. It is situated in IGNOU road, Maidan Garhi, New Delhi, India.

IGNOU gives Grade instead of giving marks. It is hard to understand for the candidates to know about those grades.

The marking system of IGNOU is as follows:

Grade A means Excellent performance and 5 Marks Equivalent to 85 % and above
Grade B means Very good and 4 marks (70-85%)
Grade C means Good and 3 marks (60-75%)
Grade D means average with 2 marks (45-60%)
Grade E means Below average with 1 marks 45% And below)
Grade O = 90%-100%

Address:
Indira Gandhi National Open University
70/79, Sector 7, Patel Marg, Mansarovar, Jaipur, Rajasthan 302020 ‎
0141 278 5730 ‎

Map:
[MAP]https://maps.google.co.in/maps?q=The+Indira+Gandhi+National+Open+University+ &hl=en&ll=27.916767,75.849609&spn=45.09139,83.6718 75&sll=24.624984,75.890931&sspn=23.520745,41.83593 8&hq=The+Indira+Gandhi+National+Open+University&t= m&z=4&iwloc=A[/MAP]