1. Optical Mark Reading (OMR) is a method of entering data into a computer system.

2. Optical mark readers read pencil or pen marks made in pre-determined positions on paper forms as answers to questions or tick list signs.

The key difference lies in when the loop condition is checked. In the while loop, the condition is checked before the first iteration, potentially resulting in zero iterations. In the do-while loop, the condition is checked after the first iteration, ensuring that the loop body is executed at least once.