| What is an error? | An event that prevents the computer from providing the expected result |
| What are transcription errors? | When the data is misread from the document and entered incorrectly |
| What are transposition errors? | Where the characters are interchanged and entered |
| What is validation? | Checking to see if the data entered is acceptable but it does not check if the data is right |
| What are the 7 methods of validation? | Range check
Length check
Type check
Format check
Presence check
Character type check
Check digit |
| What is range check? | Checks if the number entered is within the acceptable range |
| What is length check? | Checks if there are right number of characters |
| What is type check? | Checks if the correct type of data has been entered(all numbers/digits) |
| What is format check? | Checks if the data has been entered in the right pattern |
| What is presence check? | Checks if data has been entered |
| What is character type check? | Has invalid characters been entered |
| What is check digit? | An extra digit added to the end of a number, which is used to check if the barcode has been read properly |
| What are data transmission errors? | Due to external factors such as lightning, the use of other electrical devices, and other causes, one or more bits might change |
| What are the 4 methods of verification? | Parity/Parity block
ARQ(Automatic Repeat reQuest)
Checksum
Echo check |
| What is parity check? | In a parity system, for every 7 bits of data, an extra bit is sent(parity bit). This bit ensures only even/odd number of 1s has are transmitted |
| What are the disadvantages of Parity? | IF two bits are changed, error cannot b detected
It cannot be used to find which bit has changed |
| What is a Parity block? | For each block of data (block is a group of bytes) a parity bit is sent for each row and column |
| How to detect an error in even parity block? | Identify row and column with odd number of 1s, the point of intersect is the bit that has been changed |
| What is the advantage of parity block? | Parity block can be used locate the bit that has been changed |
| What is an Echo check? | Once a block has been received, it is transmitted back to the sender to compare the to sets of data |
| What is ARQ? | When a block of data has been received, the receiving computer checks for errors, if an error is not detected, an acknowledgment signal is sent in specific time, if it is not received in a specific time the same block of data is resent |
| What is checksum ? | For each block of data the total is calculated, and transmitted along with the block, the receiving computer calculates the checksum and compares with the one entered, if different error is detected |
