Converting 4 bits to 5 bits

I have values 

a=10     8    15

converted to decimal using 

a1 = dec2bin(mod(2^5+a,2^5))

even after performing ,i get only 4 bit values ,where as i need 5 bit value

please asssit

Answer 1

[Azzi Abdelmalek]

use

a1 = dec2bin(mod(2^5+a,2^5),5)

Answer 2

[John Petersen]

you only need 4 bits for values under 16. The fifth bit in your case is 0. Try a=20. and you will see the fifth bit.

[kash]

Yes i know it ,in MSB i neeed to add zero to make it a 5 bit