Hi Neelam,
There are several free software and pipelines for SNP calling. I will suggest you to read this beginners guide to SNP calling from high-throughput DNA-sequencing data. http://www.ncbi.nlm.nih.gov/pubmed/22886560 and try some...
Dear Ashwin,
There is a simple difinition:
Computational biologist: Programmer learn biology and do research.
Bioinformatics: Biologist learn programming and do research.
I guess this make sense.
Thanks