Can you explain what a swap file is and how it is used in an operating system?

A swap file is an area on the disk that the operating system uses as an extension of RAM. When physical memory (RAM) runs out, the OS can temporarily move inactive data from RAM to the swap file, freeing up space for active processes.

Using a swap file allows more applications to run than can physically fit in RAM, but disk access is slower than memory, so performance decreases when swap is actively used.

For example, in Linux, a swap file can be created and activated as follows:

sudo fallocate -l 1G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

Thus, the swap file helps the system operate stably under high memory loads.