Multiple choiceQuestion 1 · Recall
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By the end you can describe a visual check and double entry, explain what each catches, and justify which to use for a given set of data.
Lesson 1 showed the gap: a real date typed in the wrong order passes every validation rule. The value is possible, just not what the form said.
Verification at entry closes that gap by comparing what is in the system with the source document. There are two standard methods: a human visual check, or a second independent entry that the computer compares.
Visual check
A visual check means a person reads the data on screen (or on a printout) and compares it, field by field, with the original document, correcting anything that does not match.
It is cheap and needs no extra software, but it relies on concentration: the same person who typed the data is the least reliable checker, because the brain sees what it expects to see.
When you type Patle instead of Patel, reading your own work is unreliable. You already know what it is supposed to say, so your eye skips the letters.
This is why proofreading your own writing is hard.
Practical visual checking therefore works best when:
It is not practical to visually check a million order lines. That is the gap double entry fills.
Double entry
Double entry means the same data is typed twice, independently, usually by two different operators. The system compares the two versions automatically. If they match, the data is accepted; if they differ, an error is flagged and the entry is repeated or checked against the source.
"Independently" is the important word: the second operator must not be able to see the first entry, or they will copy its mistakes.
| Visual check | Double entry | |
|---|---|---|
| Who does the work | One person comparing two displays | Two people typing, machine compares |
| Cost and time | Low; one pass through the data | Roughly double the typing |
| Reliability | Moderate; depends on attention and fatigue | High for typing slips, because two independent errors rarely match |
| Best for | Short records, quick corrections, low-risk data | Bank details, medical records, exam entries, payroll |
Neither method catches an error in the source document. If the form says the wrong account number, both operators type the same wrong number and the system happily accepts it.
Both methods also assume the two copies are independent. If the second operator reads the first screen, or one person types both copies from memory, the protection collapses to a visual check with extra typing.