What happens in the process of the input and output systems?

Input consists usually data that needs to be worked upon. The input is read in and the Central Proccesing Unit works on it as per a recipe (a program) and produces an output which is displayed or otherwise made available to the person who wants it with the input he/she provided. In some cases the output from one step can become the input to another step and so on until several steps are completed before the final output is presented or made available.