Pretty much what people have been saying but the theory is quite easy, but the coursework (60% of the GCSE I think) are 2 pieces of coursework, which are very long and very arduous. A451 is the theory and is what you'll take your exam on (devices, topologies, algorithms, software stuff like that). A452 is using the Linux command line to complete tasks (Boring tasks) and A453 is programming in python (hard to get a good grade on because even if you're a master at python, you get the marks from saying what it does, making testing tables, taking screenshots and loads more).