Secondary Memory

Secondary memory is what we generally refer to when as we ask “how much space does your computer have left?”. In many cases, secondary memory is your hard drive. There can be other types of secondary memory as well which are less common such as USB drives, CD’s or external Hard Drives/SSD’s. From here on we can think interchangeably of secondary memory as your computer’s hard drive.

Computer Lifecycle

1. Your computer is off and you press the “on” button.
   1. The ROM will hold instructions that detail where to find the operating system in secondary memory.
   2. Your RAM is empty at this point.
   3. Instructions are copied and transferred from secondary memory to primary memory (RAM)
   4. RAM will not hold your whole operating system, but it will be using a good amount of RAM available for necessary tasks.
   5. There will now be some RAM available for your programs to run (browsers, VSCode, Spotify, etc.)
2. You click on Spotify to get some tunes going before a long revision sesh.
   1. Spotify instructions will be loaded on to your RAM from secondary memory.
   2. There will be less RAM available for other programs.
   3. The CPU can’t talk to secondary memory, only to primary memory. Anything you need anything new, we’ll have to fetch it.
3. You choose a new song which is has not been downloaded to your computer beforehand.
   1. The data is fetched from the internet.
   2. The song data is temporarily stored in your RAM.
   3. There is less room in your RAM for other programs.
4. Your study sesh is not going to start and you open 19 tabs on Chrome. You also open a few PDF’s and maybe WhatsApp Desktop messenger.
   1. Your RAM is now close to being full.
   2. Any programs that you open up from here on out will need to use RAM. But there isn’t a lot of it!
   3. Your computer tries to figure out which programs need the most memory. Maybe which are being used the most by you.
   4. RAM is given priority to the most used programs right now, perhaps.
   5. In the background, songs are still being downloaded on to RAM, and disposed when they are done.
   6. Messages are coming in and network calls are being performed, these also need RAM. Ah!
5. Your computer starts giving you the spinning wheel of death, why?!
   1. Your computer now has to decide which data to store in RAM and which to switch over to secondary memory.
   2. Any time that you need to use a program that has data stored in secondary memory, your computer spinsssss.
   3. This is because it takes a long time to get things from secondary memory, its faaaaaaar away.
   4. As you open up more tabs, some of those are put into secondary memory if they’re not being used.
   5. Priority continues to be given to certain programs.
6. You finish your homework and save the pdf to your hard drive.
   1. Some, or all, of the pdf data will be saved to your hard drive. This doesn’t happen immediately.
   2. Your Operating System will schedule this data to be saved at some point.
   3. Eventually, your data will be saved in your hard drive.