This memory is erased when you switch from one task to another or turn the computer off. RAM is not suited for long term storage. Most modern PCs have one or two MB of RAM, which is enough for most applications. This RAM can always be expanded to four or more megabytes. Disk storage is used for long-term storage of programs and data.
Disks retain their data for years, even after the power is removed.
However, their low cost per megabyte and high reliability make them appropriate for mass storage of data. A hard disk drive is a faster, larger storage device. While the diskettes that go into a floppy drive can be taken in and out, the hard drive generally has no removable parts. Hard drives can range in size from 20 to 1000 MB or more. Hard drives are usually 10 to 20 times faster than floppy drives.