Hello candidate,

First let me tell you about the meaning of both these terms, HCOS refers to Haryana Council of Open schooling whereas HOS refers to Haryana Open Schooling.

The Haryana Council of Open schooling or HCOS is a registered board and is widely accepted along various colleges and institutes around the country in entrance examinations as well as during College admissions.

Have a good day. Hope that this answer was helpful for you.