eli5 How does a computer store and read data?

Question

What mechanism is used for it? How does it work?

In: 2

Answer 1

Data can be stored in a dizzying amount of ways, and all data is read using logical rules.

For example – hard drives store data magnetically. Inside every hard drive is an array of disks that have billions of tiny little spots that can be independently magnetised or demagnetised. If a spot is magnetised, that is interpreted as a 1, and if it’s demagnetised, that is interpreted as a 0.

Solid state drives, on the other hand, store data electronically – it uses billions of transistors to isolate tiny little pockets of charge, where a charged pocket is a 1 and an uncharged pocket is a 0.

DVDs and CDs are also different, using optical effects to represent data – instead of magnetism, the disc is filled with tiny little pits in the surface. A laser is shone on the disc, and the light will be reflected in two different ways depending on whether it hits a pit or a flat area. Again, we now have a way of representing a 0 and a 1 for binary data.

Between 1950 and 1970, the most popular form of data storage was magnetic-core memory, where tiny little metal rings were threaded between two sets of wires to create a lattice of loops that could be physically flipped one way or another depending on the charge of the wires, and the physical orientation of the loops was used to represent 0 and 1 states.

Basically, literally any possible arrangement of things – magnets, charges, objects, whatever – that has two possible states (uncharged and charged, left and right, light and dark) can be used as a way of representing binary data. All you need is one state for zero, and one state for one. An arrangement of empty beer cans sitting on a wall, where a can is a one and an empty space is a zero, could a way of ‘storing’ digital data.

At the very simple end of things, computers ‘read’ data using the same mechanism by which computers ‘think’ – they interpret electronic signals (ones and zeroes) using logical processes, that are created using transistors; tiny little devices which can either accept, amplify, or block current. They can be chained together in complicated ways to produce logical ‘gates’ (if input A, do output B, elsewise do output C etc) that can themselves be chained together to make a device which can perform an infinite and arbitrary amount of calculations. Such a device is said to be *Turing complete.*