the part of the computer that contains the brain , or central processing unit , is also known the what ?

system unit

Explanation:

A system unit is the part of a computer that contains the brain or central processing unit. The primary device such as central processing unit as contained in the system unit perform operations hence produces result for complex calculations.

The system unit also house other main components of a computer system like hard drive , CPU, motherboard and RAM. The major work that a computer is required to do or performed is carried out by the system unit. Other peripheral devices are the keyboard, monitor and mouse.