Hello Subhayu, 

To be eligible for CDS, you must have completed your graduation degree from a recognized university or institute. So, you need to complete your graduation if you wish to apply for CDS. To know more eligibility criteria of CDS - Click Here

Hi Subhayu Ghosh,

To be eligible to write the exam, it is necessary to complete your graduation. And the Diploma is considered as equivalent to 10+2. So Diploma students are not eligible to write CDS exam. But you can write NDA (National Defence academy) Exam. Through which you can get into Navy/Airforce/Army wing.

Eligibility for NDA Exam :

1)10+2 passed or any other equivalent exam to 10+2 with physics and maths.

2)Age limit-16.5 to 19 years(at the time of commencement of the course).

Hope it helps.

Regards.