What is sentinel value?

A sentinel value is a special value that is used to terminate loops or mark the end of data in a series. This value is typically chosen because it is outside the range of valid data and can be easily identified by the program.

Sentinel values are often used in programming to simplify the logic of loops and to make handling boundary conditions easier. For example, in a program that reads numbers from user input until a negative number is entered, the negative number could be used as a sentinel value to indicate the end of the input.

It is important to choose a sentinel value that will not be mistaken for valid data to avoid errors in the program. Care should also be taken to handle cases where the sentinel value may not be present or where it needs to be handled differently than regular data.