Taxability of nsc

i have investments in NSC. I show the interest every year as income from other sources and claim the benfitu/s 80c.

However one of my NSc will be maturing in a few days time. My question is

1. Whether the last years interest would be eligible for tax benefit? or it will be taxed under the head Income from other sources?

2. What will be treatment of my principal? Shall it be taxed or it will be eligible for tax benefit too?

Please help