What is a subroutine in computer programming?

A subroutine, often referred to as a function or method in various programming languages, is indeed a set of computer instructions designed to perform a specific task. This allows a programmer to write code that can be reused multiple times throughout a program, enhancing code organization and reducing repetition. By defining a subroutine, you can call it whenever needed without rewriting the same sequence of instructions, which not only saves time but also makes the code more maintainable and less error-prone. Subroutines can also accept parameters, enabling them to work with different sets of data, thus increasing their versatility.

The other options describe different concepts related to programming but do not accurately define a subroutine. For instance, a graphical representation of a program flow pertains to flowcharts, while debugging methods focus on identifying and fixing errors in code. An unused section of code may refer to code that is never executed but does not capture the essence of what a subroutine is.