next Modulation
up CMPT 165: Review
previous Bits

Error Checking

Interference from natural phenomena, distortion from electrical or magnetic interference can cause damage or loss of data.

A parity bit is an extra bit added to a code before transmission to help the hardware detect errors. It is set to

Checksum is a technique for detecting damaged bits. The software sends the sum of the numbers in the message. If a message consists of the numbers

   1, 3, 5

the software sends

   1, 3, 5, 9

When the messages arrives, the receiving software sums all the values except the last, and then checks to ensure the sum equals the last value.

next Modulation
up CMPT 165: Review
previous Bits

``CMPT 165: Review'' by Tamara Smyth, Computing Science, Simon Fraser University.
Download PDF version (review.pdf)
Download compressed PostScript version (
Download PDF `4 up' version (review_4up.pdf)
Download compressed PostScrip `4 up' version (

Copyright © 2011-12-05 by Tamara Smyth.
Please email errata, comments, and suggestions to Tamara Smyth<>
School of Computing Science,   Simon Fraser University