Q.Which part of the computer is called the "brain of the computer"?
(A) Random Access Memory (RAM)
(B) Central Processing Unit (CPU)
(C) Monitor
(D) Hard disk drive

The "brain" is the part that does the actual processing and controls all the other units, not the parts that merely store data or show output.

The CPU interprets and executes instructions and directs the whole system, which is exactly what a "brain" does. RAM only stores data temporarily, a monitor only displays output, and a hard disk only stores files.

As Section b explains, the central processing unit (CPU) is the part of the computer that actually carries out processing — it interprets and executes instructions and controls the working of every other unit. Because it does the "thinking" and directs the whole machine, it is called the brain of the computer. In a modern computer the CPU is a single chip called a microprocessor, made up of the ALU, the control unit, and registers.

The other options are not the brain: RAM (A) is only the temporary working memory that holds data for the CPU; the monitor (C) is an output device that merely displays results; and the hard disk (D) is secondary storage that keeps files permanently. None of these does the processing — only the CPU does.

Some students pick RAM because it is important and works closely with the CPU. But RAM only stores data temporarily; it does not process it. Only the CPU processes data and controls the system, so only the CPU is the brain.