I know that block ciphers encrypts data in the shape of specified blocks and DES also belong to block cipher family. I totally understand the procedure of DES, but I am confused that is DES take all the blocks of 64 bits of any plaint text and apply the process to all of blocks at a time or it encrypts first blocks then 2nd and 3rd and so on.. can anyone explain it Please??
Guess what: in counter mode DES doesn't encrypt blocks of plaintext at all. In counter (CTR) mode DES encrypts a counter which is XOR-ed with the plaintext.
DES itself doesn't do anything with multiple blocks. DES is an algorithm called a block cipher which handles one block of input and permutes it to a block of output. The chosen permutation depends on the key.
To encrypt anything that is not precisely a block with DES (or any other block cipher) you need a block cipher mode of operation . There are many modes of operation in which a block cipher can be configured as underlying primitive.
How many bytes are actually encrypted by the mode of operation depends on the mode and implementation. One instance of DES - the block cipher - will only handle one 64 bit / 8 byte block at a time.