Don't be silly. Popular science: What's the difference between memory and storage?(1)
1. Memory and storage of mobile/computer
Nowadays, with the continuous promotion and popularization of mobile phones, the brilliance of the computer age has been concealed. Many new-generation users are confused by storage of mobile phone. We often encounter such joke that "Q: How much memory do you have in your mobile phone? A: 128GB”. We actually believe that the questioner just wants to know the phone's storage capacity, and that the respondent has answered the question in a conventional way.
In terms of the principle of computer composition, there is no essential difference between mobile phones and computers. Their main structure is still input devices, memory, calculators, controllers and output devices. As for peripheral storage devices, they are actually auxiliaries, called auxiliary storage. Just because people have more demand for results, it becomes the most important component known as storage which is visual and touchable.
The storage of computer introduced by the principle of computer composition is as follow. Storage is used to store programs and data and for a computer, it has memory function and ensures normal operation due to storage. There are many kinds of storage. According to its applications, it can be divided into primary storage, also called memory storage, and auxiliary storage such as hard disk and SSD.
After applying such a definition of memory and storage on the network, you may no longer get confused again. When the CPU processing data likes you eat peanuts in your mouth, the capacity of hard disk is the size of your pocket (how many peanuts you can place), and the memory is the size of your hand (how much peanuts you can grab at a time).
Today, DRAM technology is used in both mobile phone and computer memory. The most common system memory, DRAM, is short for dynamic random access memory. DRAM can only keep data for a short time. In order to maintain data, DRAM using capacitive storage must refresh once a time. If the storage unit is not refreshed, the stored information will be lost.
Storage are divided into two main types of technology today: HDD (Hard Disc Drive) and NAND Flash. There is no much introduction about HDD here. NAND Flash, whose full name is Flash Memory, is a non-volatile memory device. The internal storage of Flash is MOSFET, which has a floating gate, the real unit of data storage.
The data is stored as electrical charge in the Flash memory unit. The amount of charge stored depends on the voltage applied to the external gate in the figure, which controls whether the charge is charged or released into the storage unit. The data represents whether the voltage of the stored charge exceeds a specific threshold(Vth).
Data represents the comparison between the voltage of charge stored in a single storage unit, and a particular threshold voltage(Vth). If the voltage of charge stored in a single storage unite is larger than Vth, data means 1, and vice versa, less than Vth, it means 0; For NAND Flash, data written to 1 means controlling External Gate to charge. When the storage charge is enough and exceeds Vth, data is 1. For being written to 0, that represents discharging. When the charge is reduced to less than Vth, data is 0.