Error Checking for Data Transmission GCSE Computer Science

Error Checking identify and describe methods of error detection and correction, such as parity

Parity Bits Parity bits are added to bit patterns to create either an odd

Check Digits Check digits are digits added to the end of a number that

Binary Addition Checksums use binary addition to create a bit pattern to check for

Why were the bits on the left undetected? Checksums are a little more complicated

Checksums are a little more complicated than check digits. To create a checksum, the

Automatic Repeat Requests When one device sends a data packet, it waits for the

Exam Questions show understanding that sound (music), pictures, video, text and numbers are stored

Answer 1 1 = 0110001 = 49 0 = 48 = 0110000 Even parity

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Error Checking for Data Transmission GCSE Computer Science

Error Checking identify and describe methods of error detection and correction, such as parity checks, check digits, checksums and Automatic Repeat re. Quests (ARQ Click here for Topic Introduction

Parity Bits Parity bits are added to bit patterns to create either an odd or even number of 1 s in the pattern. If the receiving device detects an incorrect pattern, then it rejects the data. Why might using a parity bit be unreliable?

Check Digits Check digits are digits added to the end of a number that are created from a calculation. If the same calculation is applied to the data again, the check digit should match. How is this used for ISBNs for books?

Binary Addition Checksums use binary addition to create a bit pattern to check for errors. Adding binary is similar to long addition in denary + 128 64 32 16 8 4 2 1 1 0 1 0 0 1 1 1 0 0 1 0

Why were the bits on the left undetected? Checksums are a little more complicated than check digits. To create a checksum, the binary numbers are added together to create an extra bit pattern. By comparing the sent & recalculated checksums, columns with corrupted bits can be detected.

Checksums are a little more complicated than check digits. To create a checksum, the binary numbers are added together to create an extra bit pattern. By comparing the sent & recalculated checksums, columns with corrupted bits can be detected.

Automatic Repeat Requests When one device sends a data packet, it waits for the recipient to send confirmation that it was received. If nothing is confirmed after a set time, the packet is just sent again.

Exam Questions show understanding that sound (music), pictures, video, text and numbers are stored in different formats

Exam Question 1

Exam Question 2

Exam Question 3

Answer 1 1 = 0110001 = 49 0 = 48 = 0110000 Even parity (parity bit on the left) = 00110000

Answer 2 4 2 1 9 2 3 24 10 4 27 4 3 R=6 Valid = false = 72 =6

Answer 3 8 2 0 1 5 6 48 10 0 3 10 6 R=0 Valid = true = 77 =7