Bit

Here is a table that summarizes the characteristics of the two types of computer memory.

Characteristic	True for Main Memory	True for Secondary Memory
Very closely connected to the processor.	X
Holds programs and data that the processor is actively working with.	X
Used for long term storage.		X
The processor interacts with it millions of times per second.	X
The contents is easily changed.	X	X
Relatively low capacity.	X
Relatively huge capacity.		X
Fast access.	X
Slow access.		X
Connected to main memory.		X
Holds programs and data.	X	X
Usually its contents are organized into files.		X

In both main and secondary memory, information is stored as patterns of bits. Recall from chapter two what a bit is:

A bit is a single "on"/"off" value. Only these two values are possible.

The two values may go by different names, such as "true"/"false", or "1"/"0". There are many ways in which a bit can be implemented. For example a bit could be implemented as:

A mechanical electrical switch (like a light switch.)
Voltage on a wire.
A single transistor (used in main memory).
A tiny part of the surface of a magnetic disk.
A tiny part of the surface of a magnetic tape.
A hole punched in a card.
A tiny part of the light-reflecting surface of a CD.
Part of a radio signal.
Many, many more ways

So the particular implementation of bits is different in main memory and secondary memory, but logically, both types of memory store bits.

QUESTION 3:

(Thought question:) Does the information change when a bit is copied from one form of storage to another? For example, does the information change when a bit implemented as a voltage level on a wire is copied to a tiny part of a disk?

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