There is no requirement before studying GCSE Computing. The qualification is intended to introduce all students to important key concepts and skills relating to computing. It is not a specialist qualification. The skills are transferable to a wide range of work and careers.
The amount of content is well balanced by the exam boards so that it is not long or heavy. The exam durations and content are reasonable as well - with exam papers varying in duration between 1 hour 30 minutes and 2 hours.
There is one part of GCSE Computing that could be more difficult to study - that is the necessity and importance of practical practice. Subjects that have more emphasis on memorization of facts make it easier for students to cram or revise before an exam even if they were not consistently studying during the year. However, OCR, AQA and Edexcel all have practical practice as part of their exams. The consequence is that it is more difficult to revise for GCSE Computing in the last minute because students won't have the habits of problem solving and programming to help them during the exam. If there is one difficult part of GCSE Computing, it would be the necessity to revise and practice on a regular basis rather than cramming just before the exams.