Question

Describe the difference between single, double precision and residue checksum. Give an example (numerical)

Please do not copy from internet and need it typed not hand written

Answer 1

Single precision checksum is formed by adding the data words and ignoring the overflow.

0111+0001+0110+1000=0110(checksum) (carry is ignored)

The single precision checksum is unable to detect some errors. The received checksum and the checksum of original data are same and so no error is detected.

Original data

0111+0001+0110+1000=1110(checksum)

Received data

1111+1001+1110+1000=1110(checksum of received data).

A double precision checksum is done by adding the data by double precision arithmetic. Here the received checksum and checksum of received data are not equal and hence error is detected.

Original data

0111+0001+0110+0000=0000 | 1110 (checksum)

Received data

1111+1001+1110+1000= 0010 | 1110 (checksum of received data)

Residue checksum

Residue checksums are similar to the single precision checksums except that the most significant bit position is not ignored but is added back to the checksum in an end around carry fashion.

Carry from

addition----

|

Word1+ word2+...+word n= sum of data = checksum

The residue checksum is formed by end around carry addition so that the information in the carry bit is not lost.

00010111

0001

0110

1000