Before SSDs, computers stored data using paper holes, sound waves, and tiny magnets — every step bringing us closer to modern storage.
punch cards
was the the way to store data for long time like right now ssd,hdd. it had holes where computers read that from light sensors.
Delay line memory
then delay line memory came where data is passed through speaker to microphone and it continue and loop and one wire was connected to read the data.
and created first computer EDVAC.
Magnetic Core Memory
new kid one the block. it noticed that when electricity is prassed through magnet it changes polarity.it was revolutionary now changing polarity can led to 1 and 0!.
Depending on how it was wired, core memory could be exceptionally reliable. Read-only core rope memory, for example, was used on the mission-critical Apollo Guidance Computer essential to NASA's successful Moon landings.
project idea to make a storage device at home ;)
How a works
there are wires horizontaly and verticaly.
reading-
The computer forces the selected core to 0 using horizonal and vertical wires.
and there is a signal wire reads data - If the core was already 0 → no change, no signal. - If the core was 1 → it flips to 0. - That flip creates a voltage pulse in the sense wire. - Pulse = 1, No pulse = 0.
After reading, the core always ends up as 0.
writing:-
1/2 half current is passed through horizontaly wire. and 1/2 half current is passed through vertical wire. so it hit exactly that magnet which turns it on.
half current :- it need 10 amps to turn a magnet on so it sends only 5 amps from one wire and 5 apms from another. note:- if we send whole current through one wire all magnet turns on.
isent its so slow to write one by one?
yeah its a headache to write one by one magnet so they used 8 layers of core memmory. so if you wanna write 8 bit word it write it in 8 layers instantly. BOOM FAST
Magnetic Tape
new we getting to the era where we actually see the things in real aka magnetic tape.
The "Tape" itself is a long ribbon of plastic. One side is coated with a thin layer of magnetic material. This material is made of billions of tiny magnetic particles that act like microscopic compass needles. When the tape is "blank," these particles are oriented randomly.
Write Head:- when recoding medium is passed through write head it creates a gap of magnectic with electrictiy which changes the polarity of magnetic strip of recording medion.
which result in 1 and 0. its non-volatile , and the reading is non destructive!
NOTE :- THIS IS HOW HARD DRIVE GOT INSPIRATION FROM.
Hard Drive
hard drive also work with magnetic field. there is a magnetic disk in hardrive and a a head write data in it by changing its polarity but mordern hardrives are so fast they can store trillion bits of data.
reading: then to read data there is a reading sensor.
when it want to read data it passes it through it changing the data from 1 to 0 (left to right) or 0 to 1(right ot left) if its already 1 no electric pulses if it change to 0 boom magnetic pulse .
if iand the disk makes a pulses which the HDD’s controller convert it into electric signal converting into 1 and 0.
BOOM WE GOT DATA AGAIN.
