What is the difference between block cipher and stream cipher?

Answer 1

Stream cipher is one that encrypts a digital data stream one bit or one byte at a time

Block cipher is one in which a block of plaintext is treated as a whole n used to produce a ciphertext block of equal length

hmmmmmmm got it!!!

Answer 2

A block cipher divides plain text into a sequence of text groups. It operates on each group to encode it, gives it to output, and restarts with the next text group.

A nontrivial block cipher could perform several complex transformations of the grouped text in a sequence. A trivial block cipher could reverse the order of the text characters in every group of six characters. "This is a nonsensical test." could be encoded as "i sihTon a sisnesnet lac.ts"

A stream cipher operates continuously on incoming text. As it examines each character, it operates on it and sends it to output, and continues without restarting.

A nontrivial stream cipher could examine a group of characters starting at the current character, and operate on the group to send an encoded character to output, discarding the current character and fetching the next character ahead of the group. A trivial stream cipher could send the character that alphabetically precedes each character of text. "This is nice" could be encoded as "Sghr~hr~mhbd"