Non-Volatile Memory Fundamentals

Non-Volatile Memory

• Memory volatility refers to a memory's ability to retain information without a constant power supply.
• A non-volatile memory example is a piece of paper, as it can store information indefinitely without power.

Punched Cards

• Punched cards were an early method of storing data, with each hole representing a single bit.
• The values of the bits were determined by checking whether the holes were punched or not.
• Punched cards were inefficient, requiring manual labor to convert programs into binary and punch holes for each bit.
• Errors, such as mistakenly punching a hole, required starting over from scratch.
• Keeping the cards in order was crucial for the program to work correctly.

Magnetic Tapes

• Magnetic tapes were a later development in non-volatile storage, consisting of a magnetizable sheet divided into small slots, each representing a bit.
• Information was stored by changing the magnetic polarization of the sheet, which could be detected and changed by the reading/writing head.
• Magnetic tapes are durable and were used by companies and government bodies as a backup solution due to their durability.
• However, magnetic tapes are slow due to the mechanical movement required for data access.
• They also have limited storage density and are susceptible to external sources of magnetization and mechanical damage.

Floppy Disks

• Floppy disks are a type of magnetic storage that divides data into circular tracks, which are further divided into slots.
• The reading/writing head is movable, reducing the time it takes to access data.
• However, access is still slow due to the mechanical movement of the disk and head.
• Floppy disks are susceptible to magnetic and mechanical damage.
• Access speed is affected by the device's ability to spin the disk, measured in RPM (Rounds Per Minute).