Quick question on sentinel values (1 Viewer)

[Drewk]

I am struggling to under stand what sentinel values are and what priming readings are could someone please explain in simplified terms
Thanks

 

[Bolt]

A sentinel value is a predetermined value that halts execution of the program when read.

For example, a module may write integer data from an array into a database until it encounters the sentinel value, predetermined to be (for example) 'xxxx'. This basically acts as an EOF marker.

I've never come across priming readings before...