Main Memory RAM

Main memory, also called RAM (Random Access Memory), is the store that holds the instructions and data the processor is using at that moment. If you are editing a podcast in an audio app, the app's instructions and the recording you are trimming are held in RAM so the processor can work on them quickly. Main memory sits outside the CPU: the processor fetches what it needs from RAM while it works.

RAM holds only what is currently in use. Programs and files you are not using stay in longer-term storage, such as a hard drive or SSD, until you open them, which keeps RAM focused on the job in hand.

Why RAM is volatile

Volatile means RAM needs power to keep its contents. Switch off the computer, or lose power suddenly, and everything in RAM is lost. This is why an unsaved spreadsheet disappears in a power cut: the changes were in RAM but had not been copied to storage. Saving writes a copy to storage, which keeps its contents without power.