What is a "memory device" (or "memory")

Requirement of a "memory device" (or "memory")
 

Memory device used by the computer

Device used as computer memory:

Memory device used by the computer

How a switch is used as computer memory:

How to build a larger computer memory element (that can remember more states)
 

A memory element made with n switches can take on (= remember) one (= 1) of 2n possible states

How to build larger memory elements - Example
 

Computer Jargon: Bit (binary digit)
 

Computer Jargon: Byte

Purpose of the computer memory
 

Recall: what can the CPU do with the memory ? (1) get an instruction from memory
 

Function of the computer memory - (1) store program instructions
 

The computer memory enables the CPU to retrieve program instructions that it need to execute:

Recall: what can the CPU do with the memory ? (2) get data from memory
 

Function of the computer memory - (2) store program variables (data)
 

The computer memory enables the CPU to retrieve/store variables (data) for computations:

Helpful illustration on RAM