FAQS - SYSTEM CLEANING
PC AND MAC CLEAN UP
See SMART device refresh for device process. So yes, Mac's get clogged up with rubbish over time and need cleaning up and refreshing just like PC's and Smart devices. Smart devices are just small and simpler versions of their big brother computers, so the steps are similar.
Cleaning/deleting/removing/backing up: the system and website cashes, all those downloaded files from emails and websites, system and application updates, old applications/apps that you don't use, old disk images, do you update a mobile using a computer-delete the software downloaded for that. Old backups, do you need them all. The bigger steps, system refreshing, or full operating system reinstall or install on a new hard drive. Yes, even Mac's need a reinstall now and then, just like Windows. 1-2 years to keep things fresh.
ONE REASON FOR A COMPUTER SLOWING
Your hard drive is getting full and the computer is running out of space. To work your computer during the normal operation of how it does things is writing and reading data, to and from the hard drive. It allots a set amount of space to do that, when it runs out your computer goes slow.3 solutions.
1 Delete stuff you don't need off the drive to make space, either manually or with the help of a computer cleaner program.
2 add another hard drive, internally or externally, that you can move data to and store all those cat photos, and videos of little Tommy, so your main drive can be used mostly for the operating system.
3 Get a new, bigger hard drive and either migrate your current system to it or take the chance to do a fresh install - keeping your old drive as backup for the data on it, have it as an internal or external spare/backup drive.