Wait, before you jump into the conclusion that this blog is about the biology of human brain, stop. However, it is more about the marvels/wonders of the human brain and to get a better understanding of how brains/computers work similarly. It is going to be multi-part rambling about humans/brain/systems. It may help you understand computer systems better than help you understand the brain better :-), as they say 'it depends' ;p
Disclaimer: There may be some technical jargons that will be found occasionally. All efforts would be made to explain them, in the limited scope of the blog.
Human brain, as all of us know, is essentially like the software that runs on your body (hardware). As a computer is represented in a block diagram, the brain does the functions of processing stimuli (all types like visual,audio etc) , memory and the nerve cells (spinal cord is a nerve bundle) which act as the 'carrier' of the stimuli/messages to&from the brain.
First up - think of this, like any 'system', the processing/memory/messaging have to work in perfect harmony for the information you ask for to be readily available.
Loss of memory, is the easiest thing one can think of amongst the system, since it seems like the most frequent thing. As with any 'system' information organised in a file can be considered the 'finest' atom that the system keeps track of for the purposes of 'indexing a.k.a table of contents' i.e. when you say get me the list of files in c:\temp -> you a table of content for that folder which says what are files that are contained in that folder. All one has to do to 'lose' the file is to 'un-register' the file from the table of contents i.e. remove the linkage. So that, even if the information is physially available on the system - it is no more 'reachable'. This exactly is what happens when you 'forget' something for good. We will talk more about memory and the loss of it, and how via hypnotism, one can 'seemingly' bring it back. (and no, am not a hypnotist)