What makes one algorithm better than another?

There are two main aspects which make an algorithm better than another. The first one I would like to discuss is the measure of how efficient an algorithm is in terms of the time the algorithm takes to complete its calculations and come to a result (an end).

Consider the examples as outlined by Brookshear (2009) of a binary search and a sequential search for a specific item in an ordered list. While the sequential search runs through a list one by one until it finds an entry, on average this search will search through at least half of the list – if the list is very large this may add up to quite a sufficient amount of time per search. A binary search divides a list into two, looks at the middle entry and calculates whether the result is in the first or last half of the resultant lists, then further breaks the respective half in half again, and repeats this process until it finds the item it is looking for. One can plainly see that the binary search method will access a record far less times on average than the sequential search.

Another aspect of measurement is the physical space the algorithm consumes when performing its calculations/operations. A very simple way of explaining this is the one of sorting a list alphabetically. The two methods are firstly the bubble sort versus secondly creating a new list in the correct order. In the bubble sort the method is to sort the list in the form of looking at it in small pieces and sorting them by shuffling around the entries until the entire list is sorted. This way we only occupy the memory/space of the original list. In the method of sorting into a new list, the memory occupied by the original list is used and another entire list is created from the same entries sorted into the correct order. The latter occupies double the amount of memory than the former.


Brookshear, J.G (2009) Computer Science: An Overview. 10th ed. China: Pearson Education Asia Ltd.


The conflicting, dual definitions on the purpose of an Operating System

I was posed this question in my studies. An operating system is said to have two, conflicting definitions of purpose:

  1. Presenting a virtual machine with a user-friendly GUI to a user which isolates them from the low-level hardware
  2. It must manage, efficiently, the limited resources of the hardware system

Firstly I tend to agree that the two conflict in nature. If we think of the operating system on the whole and then think of the goal of efficiently managing resources it will not take long to realise that the nature of an operating system is not entirely geared towards efficiency. On the surface the limited resources of the computer are often wasted on things like graphical effects and enhancements like transparency and animation. Often the resources required to perform these seemingly meaningless tasks are very taxing on the system hardware.

If I look at the question again, the phrase “manage in the most efficient way the (always) limited resource of the computer system” (University of Liverpool, 2010), I would say that it does manage the resources of the operating system quite efficiently, because, regardless of the task at hand, the computer manages to operate quite smoothly when doing its multi-tasking and just looking at the task manager in Windows 7 you are able to see just how many tasks are running at any one time, and the computer still operates responsively and seemingly effortlessly. What I’ve just mentioned does entirely depend on the spec of hardware that your computer is running, RAM and CPU speed etc. but if you follow the minimum requirements performance is generally as it is expected.

My conclusion is that I do think that they work together quite effectively as, in this specific answer of mine, Windows 7 as an operating system is very user friendly while still managing the computers resource efficiently and quickly (despite its predecessor, Vista, which did not manage resources as well). The concept of a process is absolutely vital to the success of both managing the hardware efficiently and providing a user friendly environment. A process is defined as a dynamic activity who’s properties change as time progresses (Brookshear, J, pp.134), coupled with multiprogramming is a way in which different activities and resources are managed and organised, without this there would be chaos and I believe the computer would be sent back to the days of batch processing single tasks.


Brookshear, J.G (2009) Computer Science: An Overview. 10th ed. China: Pearson Education Asia Ltd.