What can perform many computer functions. Mainframe computer is powerful, used by large organizations to process large amounts of data. Super computer is very powerful for complex calculations and scientific research.

The text describes three types of computers:

• A general-purpose computer that "can perform many computer functions."
• A "Mainframe computer" used by large organizations to process large amounts of data.
• A "Super computer" for complex calculations and scientific research.

Based on the provided characteristics, here are the completed descriptions:

• Personal Computer (PC): A general-purpose computer designed for individual use that can perform many computer functions.
• Mainframe Computer: A powerful computer used by large organizations to process and store large amounts of data, often for critical applications.
• Supercomputer: A very powerful computer designed for complex calculations and scientific research, capable of extremely high computational speeds.