12 December 2011
No you can not purchase share of a listed company because they are in de-materialisted form. You can buy shares of Non listed company which is available in physical form by paying cash or Cheque, as rightly said by Anurag.
26 December 2011
The shares can be bought and sold through ur Demat Account. The demat account is linked to the Bank Account now a days. so that if u want to purchase or sell a share(Short sell) u can transfer cash from Bank to Demat account and carry out the transaction.