Hi Shreyas
Checksum is one of the error detection techniques used in digital communication. It is the one's complimemt of the sum of two or more words/bytes. For example:
If you need to generate a checksum for two bytes, say 11001010 and 01010101, then you need to perform binary addition on them i.e.
11001010
+
01010101
=
00011111, now taking its one's compliment (or simply inverting the bits) we get: 11100000. This result is the required checksum.