Question

What is a sentinel?

Short answer

A sentinel is a special value used to indicate the end of a sequence or signal a specific condition in a programming algorithm. It is often used in loops and helps prevent errors caused by processing beyond the intended range of data. For example, in a program that takes a series of integers as input and calculates their sum, a sentinel value (-1) may be used to indicate the user doesn't want to provide any more numbers. The sentinel allows algorithms to handle input of unknown length efficiently.

Step-by-step solution

Define Sentinel

A sentinel is a special value that is used to indicate the end of a sequence or to signal a specific condition in a programming algorithm. It is often used in loops and helps to prevent errors caused by processing beyond the intended range of data. Sentinels are important because they allow algorithms to handle input of unknown length efficiently.

Example of Sentinel Usage

Imagine a program that takes a series of integers as input and calculates the sum of entered numbers. The user will enter -1 to indicate they don't want to provide any more numbers. In this case, the sentinel value is -1. Here's an example of how this might look in Python: ```python sum = 0 number = int(input("Enter a number (-1 to quit): ")) while number != -1: sum += number number = int(input("Enter a number (-1 to quit): ")) print("The sum of the entered numbers is", sum) ``` In this example, the sentinel value -1 is used to signal the loop should exit, and the program should stop accepting more inputs.