What is the use of Big O notation in computer science?

Big O notation is a mathematical concept used in computer science to describe the efficiency of algorithms in terms of their time and space complexity as the input size grows. It provides a high-level understanding of how an algorithm's runtime or memory usage increases as the size of the input increases, which is crucial for assessing the scalability of algorithms.

When utilizing Big O notation, it allows developers and computer scientists to compare the efficiency of different algorithms objectively, which is essential for optimizing processes and choosing the right algorithm for a given problem. For instance, an algorithm with a complexity of O(n) will grow linearly with the input size, while one with O(n²) will grow quadratically, indicating that the latter will become inefficient much faster as inputs increase.

The other options do not accurately capture the primary role of Big O notation. Defining application structure, helping with error tracking, or analyzing hardware performance issues are separate aspects of software development and computer science that Big O notation does not address directly. This notation specifically focuses on measuring and conveying an algorithm's performance relative to the size of its input, making it a critical tool for evaluating algorithmic efficiency.