Cómo las computadoras guardan datos

A computer's memory stores and manages our data in two main ways: persistent and volatile memory. Understanding how these two types of storage work enhances our understanding of computing and optimizes our everyday digital practices.

What are the differences between persistent and volatile memory?

Persistent memory refers to memory that retains information after the computer is turned off. For example, when you save a document, it is stored on the hard disk and persists even if you turn off your computer.

Volatile memory, on the other hand, loses its data when you turn off the computer. If you have an unsaved document in RAM and you turn off the computer, that information will disappear immediately.

What types of volatile memory are there?

The best known and most widespread type of volatile memory is RAM, which is responsible for keeping our applications active. But it is not the only one:

• Cache or CPU registers: small memories integrated inside the CPU chip, extremely fast and fundamental for the internal processing of the computer.

What formats exist in persistent memory?

The most common persistent memory is the hard disk, although it is not the only one:

• BIOS: memory that initializes the entire computer system.
• Firmware: small software present on microchips with specific functions.
• Mechanical hard disks: devices that store information by means of magnetic disks and read heads. Their speed depends on the disk revolutions.
• Solid state disks: without mechanical parts, they store information by means of electronic chips, allowing higher speeds by moving their data with the speed of electricity.

When we talk about storage units in Spanish, we generally say "disks" even if they have no physical moving parts, unlike in English where the term drive is used.

What are file systems and which are the most popular ones?

File systems organize blocks of information within persistent storage. The most commonly used are:

• FAT32: common on USB flash drives, with limitations such as maximum file size (4 GB) and no security.
• NTFS: used by modern Windows, faster, allows security and access permissions.
• EXT3 and EXT4: popular in Linux, offer extensive security measures and permissions.
• APFS (Apple File System): used by Apple devices such as Macs, iPhones and iPads.

These systems create an index at the beginning of the storage that records the exact location of each file.

What actually happens when I delete a file?

When you delete a file, you simply remove the index link that indicates its location. The data remains until it is overwritten by another file:

• The deleted data remains as "orphaned" information.
• The blocks are dispersed over time, generating slowness in mechanical disks. To counteract this, defragmentation existed.
• On solid disks it is not critical because access to data is much faster as there are no moving parts.

Why is it important to take memory access speed into account?

Each type of memory has different access times:

• CPU cache or register: 1 to 20 nanoseconds.
• RAM: 70 nanoseconds.
• Solid disks: 100 to 500 microseconds.
• Mechanical disks: considerably slower due to mechanical movement.

Therefore, whenever the system needs more memory than is available in RAM, a special space on the disk called Swap is used, although this is much slower.

What does it mean to encrypt information on a disk?

Encrypting information allows you to restrict access to data using a specific algorithm and keys, ensuring privacy and security on Windows, Mac, Linux and mobile devices.

What is garbage collection in programming?

It occurs when RAM memory is filled with data that is no longer useful if it is not properly freed. Modern programming languages have automatic processes to manage this, called garbage collection, which effectively manage this resource.

How are memory and processors evolving?

Technological advances are integrating memory and processing into single components such as the memristor, combining storage and computation. Although not yet widespread in the market, they are expected to be the future standard, integrating CPU and RAM in a single part. Other current examples of internal integration are the System on a Chip commonly used in smartphones.

Would you like to know more technical details about these components or do you have any personal experience with them? Share your thoughts in the comments.