1.3.5 (a): describe the principles of operation of RAM and ROM

There are two types of RAM: static RAM and dynamic RAM.

RAM and ROM are both primary storage (memory)

RAM = random access memory (RAM)is volatile memory used to store data files or part of an operating system which is currently in use. It can be both read from and written to.

-volatile means it's temporary memory. So the contents of the RAM will be lost, when power to the RAM goes.

-RAM never runds out, but it gets slower through time.
-As RAM becomes full, the processor has to access the Hard-Disk Drive (HDD, also secondary storage) to replace old data on the RAM with new data.
-But by increasing the RAM size, the number of times this access operation is done is reduced, making the computer run faster.

DRAM

Dynamic RAM (DRAM) chips are made up on numerous capacitors and transistors.

Capacitor = Holds a bit of information (0 or 1)

Transistor = Like a switch; it allows the control circuitry on the chip to read from or write to a capacitor

-DRAM needs to be refreshed constantly (capacitors need to be recharged). Every 15 microseconds. If they aren't. The capacitors will lose their charges and their values will 0's

SRAM

Static RAM (SRAM) doesn't need to be refreshed.
-Instead of capacitors and transistors, SRAM makes use of "flip flops" to hold bits of memory.
-SRAM also provides faster access speeds 
>DRAM access speed is normally 60 nanoseconds
>SRAM access speed is normally 25 nanoseconds.

ADVANTAGE OF DRAM
-Less expensive to manufacture
-Consumes less energy
-Has a higher storage capacity

ADVANTAGE OF SRAM
-Doesn't need to be refreshed.
-Data access is faster.

ROM

Read-Only Memory (RAM) is non-volatile memory used to store the start-up instructions for a computer system (e.g BIOS). It can only be read from.
-Data isn't lost when power is turned off.

Application of RAM and ROM

Lets say a toy car has a circuitry which contains a RAM chip, a ROM chip and a SSD.

The ROM chip will store the factory settings and the start up routines

The RAM chip stores the instructions sent from the controller

The SSD will be used to store the instructions to operate the car.

And finally, suitable input device. Like a touch screen as there aren't many buttons