this video is part of a four part series on thinking ahead here we discuss the nature benefits and drawbacks of caching so caching is an excellent example of how thinking ahead is actually implemented in computer architecture instructions or data retrieved from secondary storage and placed into main memory often remain there in case they're needed again before the program using them ends caching results therefore in faster retrieval times as instructions or data don't need to be fetched from secondary storage which was much slower a more advanced version of this concept is prefetching which involves data being requested from main memory by the processor before it's even actually required now although it's much quicker to access items from main memory than secondary storage it's far quicker still to access items from registers or dedicated cache memory located on or near the processor of course for prefetching to work clever algorithms need to be designed to predict with a high degree of certainty that an instruction or piece of data will soon be required a good real life analogy of cashing could be queuing to purchase tickets you could take your wallet out of your pocket and your payment card out of your wallet so you do not have to waste time finding it when you finally reach the front of the queue caching is also used with websites to reduce the number of requests from the client back to the web server and vice versa overall caching is a good thing as it tends to improve speed and overall efficiency however there are potential drawbacks the nature of predictive logic means caching algorithms can be very complicated to implement the wrong data is often fetched and cached and subsequently it has to be removed or flushed from the cache maintaining the correct sequence of instructions or data items in these circumstances can prove to be problematic having watched this video you should be able to answer the following key question what is caching and what are some of its potential benefits and drawbacks to help get your head around everything to do with computational thinking we have a freely available downloadable cheat sheet it's got two sides to it there's a basic poster that reminds you at a top level what the five different strands are and on the back there's a much more detailed explanation this resource is completely free from student.craigandave.org just scroll down and select the section that says a level revision you will then see a section called ocr as a level and there's a number of cheat sheets in there including two versions of the computation one just click download to get the zip file you