Two-pass verification

On the second pass through the batch, an operator at a separate machine, called a verifier, entered the same data.

In that mode, it read a completed card (record) and loaded the 80 keystrokes into a buffer.

A data entry operator reentered the record and the keypunch compared the new keystrokes with those loaded into the buffer.

If a discrepancy occurred the operator was given a chance to reenter that keystroke and ultimately overwrite the entry in the buffer.

[2] While this method of quality control clearly is not proof against systematic errors or operator misread entries from a source document, it is very useful in catching and correcting random miskeyed strokes which occur even with experienced data entry operators.

Two women entering data onto punched cards at Texas A&M in the 1950s. The woman at the right is seated at an IBM 026 keypunch machine. The woman at left is at an IBM 056 Card Verifier. She would re-enter the data and the '056 verifier machine would check that it matched the data punched onto the cards.