Like USB flash drives, SSDs use flash memory to store data. This type of storage means that SSDs are very fast, silent, and resistant to shock.

While SSDs have come down in price, they are still much more expensive and often have lower capacities than HDDs (hard disk drives).

SSDs are often inside a computer attached to the motherboard. But there are some external SSDs that connect to the computer with a USB cable.

SSDs are a non-volatile type of storage. This means that, unlike RAM, SSDs will retain any data that's written to them, even after the computer is shut down.

Related Tech Terms:

• HDD Solid State Drive Definition
• RAM Definition
• PRAM Definition

HDDs consist of one or more magnetic platters sealed in an air-tight casing to protect it from dust. There is a magnetic head attached to an arm that moves across the rotating platter and writes data to it. The same magnetic head can also read data that was written to the disk.

HDDs are often inside a computer attached to the motherboard, or in an external case connected by a USB cable.

While HDDs are much slower than modern SSDs (solid state drives), they can have higher capacities, and are often cheaper. Because storage is cheaper for HDDs, they are often used to store data that isn't used often, or as long term backup.

HDDs are a non-volatile type of storage. This means that, unlike RAM, HDDs will retain any data that's written to them, even after you shut down the computer.

Related Tech Terms:

• SSD Solid State Drive Definition
• RAM Definition
• PRAM Definition

RAM stores important information that the computer needs to access often so that everything runs smoothly. All modern computers and phones need some amount of RAM to function.

Though computers and other devices have other forms of storage like an HDD (hard disk drive) or SSD (solid state drive), RAM is much faster. In fact, RAM is about 30 times faster than modern SSDs.

While RAM is very fast, it is a type of volatile memory. This means that it only stores information while the computer is on. Unlike an HDD or SSD, once you shut down your computer, everything stored in RAM is lost.

Related Tech Terms:

• PRAM Definition
• HDD Hard Disk Drive Definition
• SSD Solid State Drive Definition

Modern Mac computers don't use PRAM. Instead, they use NVRAM, or non-volatile random access memory.

But PRAM and NVRAM serve the same function. They both store some important information about your system like the startup disk, timezone, and so on.

If you're having some issues with your Mac computer, you may want to reset the PRAM / NVRAM. Here's how to do that:

1. Shut down your Mac computer
2. Turn on the computer, and immediately hold down these keys: Option + Command + P + R
3. Hold down the keys until you hear the startup sound after about 20 seconds

Here's a video that goes over how to reset the PRAM / NVRAM and SMC (system management controller):

Related Tech Terms:

• Macintosh Definition
• RAM Definition

Subnet masks are used when subnetting, which is when you break a network up into smaller networks. By adjusting the subnet mask, you can set the number of available IP addresses within a network.

For example, a common subnet mask for simple home networks is 255.255.255.0. This subnet mask allows up to 254 usable IP addresses within the home network. In other words, up to 254 computers, phones, and other internet connected devices can connect to your router/network and access the internet.

A simple network / subnet. Source: What Is My IP Address?

Subnet masks break an IP address up into network bits and host bits. When a device sees the network and host bits of another device's IP address, it can figure out if the other device is part of the same network (home, business, etc.), or is somewhere else online

An IP address and subnet mask. Source: IPv4

Check out this article for more information about subnets, subnet masks, and how they work.

Related Tech Terms:

• Subnet Definition

A simple network / subnet. Source: What Is My IP Address?

Subnets make networks more efficient by simplifying routes from one computer or server to another.

Also, because subnets allow us to break up networks into smaller ones, they've dramatically increased the number of devices that can connect to the internet.

Without subnets, every internet connect device would need its own IP address. There are only about 4.2 billion possible IP addresses under the current IPv4 system, so we would have run out many years ago.

Subnets often work with a subnet mask, which acts as a soft of filter for internet traffic. Using an IP address and a subnet mask, devices can figure out of another device is part of the same network (connected to the same router or within the same company), or is somewhere else online.

An IP address and subnet mask. Source: IPv4

Check out this article for more information about subnets, subnet masks, and how they work.

Related Tech Terms:

• Subnet Mask Definition

Most commonly ping refers to the act of sending a packet or signal to another device and listening for a response. This is usually done to measure the speed of the network, or to determine the status of a computer or server.

The term ping was coined in the early 1980s by Mike Muuss, who chose the word because of its similarities to the way sonar works and sounds. Muuss also developed the first ping program to diagnose network issues.

A version of the ping program should be installed by default on all modern operating systems.

To use ping, just open the command line for your system and type ping followed by an IP address or a host name, then press enter. To exit the ping utility, just press CTRL + C.

For example, if you run ping www.freecodecamp.org, you'll see something like this:

Each line shows information for each probe or ping packet that's sent out. Some of the post important information is at the end of the line. This shows the time in milliseconds it took to send out a packet and receive it back from the other server or computer.

And when you stop the ping utility, you'll see a summary of all the ping attempts:

Ping can also refer to the latency or response time of a network itself. This definition is usually used in online gaming, where ping represents the response time between the gaming client (a console or PC), and the game's servers.

In this context, high ping (>= 150ms) means that there will be a large delay between a player's action in the game and the game's response. And low ping (around 20-50ms) means that the time between a player's action and the game's response is minimal.

URLs are sometimes called web addresses. Like street addresses, URLs are unique, and lead to specific online resources. These resources could be HTML or CSS files, API endpoints, and much more.

Here is the URL to freeCodeCamp's homepage: https://www.freecodecamp.org/

Tim Berners-Lee created the first specification for the URL in 1994. It built upon the existing domain name structure and added slashes (/) to separate directory and file names like computer file systems.

URLs are made up of several parts, and always include the scheme/protocol, domain name, and path to the file or resource. They may also include the port, parameters, and anchor:

_Source: What is a URL?_

The domain names of a URL can be broken down further into a subdomain, second-level domain, and top-level domain.

For example, the freeCodeCamp forum is located at https://forum.freecodecamp.org/.

In this URL, forum is the subdomain, freecodecamp is the second-level domain, and .org is the top-level domain.

The subdomain is a division of the whole domain, and is a bit like a room in a house. Similar to how a bedroom and bathroom serve totally different purposes, different websites or applications can exist on each subdomain. Common subdomains include www, blog, shop, and m for the mobile version of a site.

The second-level domain is the name of your website or resource, and is how people will find it online. Second-level domains are usually the names of people, companies, or organizations.

The top-level domain, or TLD, can give people some information about your company or organization. For example, .com is a generic TLD that can be used for everything from personal sites to online stores. Meanwhile, .org is meant for nonprofit organizations and communities.

These days there are many different TLDs like .dev, .tech, and .rocks.

Binary is base-2, meaning that it only uses two digits or bits. For computers, 1 is true or "on", and 0 is false or "off".

The concept of binary and bits are based on of Boolean Algebra.

The binary number system is positional. So even though it only works with 1's and 0's, the position of those two digits can represent much more.

For example, here are the numbers 0 to 10 in binary:

And things like ASCII work with binary under the hood.

In fact, while computers work with all sorts of different input and output, at their core, they work entirely with binary.

To get a high-level overview of how computers work and binary is used, check out this video:

Related Tech Terms:

• Bit Definition
• Boolean Definition

Natural numbers are sometimes called positive or non-negative integers.

For example, 3, 16, 512, and 1,382,437 are all considered natural numbers. -2, 4.25, and 18,512.5 are not.

The number zero may or may not be considered a natural number, depending on the definition of natural number being used.

For instance, if natural numbers are defined as non-negative integers, then zero can be considered a natural number (0, 1, 2, 3, 4...).

But if natural numbers are defined as positive integers, then zero is not considered a natural number (1, 2, 3, 4...).

In computer science, some standards like ISO 80000-2 define zero as a natural number.

Related Tech Terms:

• Rational Number Definition
• Irrational Number Definition
• Integer Definition
• Floating Point Definition

In other words, an irrational number cannot be expressed as a fraction ratio of two integers.

Famous examples of irrational numbers include pi (π), Euler's number (e), and the golden ratio (φ).

For example, pi is often shortened to 3.14159, but is actually an infinite series of numbers. And unlike a rational repeating decimal number such as 0.3333333..., pi does not end with a series of repeating numbers.

Also, almost all square roots of natural numbers are irrational. Only perfect squares are not irrational numbers.

For instance, unlike the perfect square root of 4 (2²), the square root of 3 is 1.7320508..., or about 1.73.

Related Tech Terms:

• Rational Number Definition
• Natural Number Definition
• Integer Definition
• Floating Point Definition

For example, 3/4, 8.75, 2, and -6 are all considered rational numbers.
Note that integers, or "whole numbers", are rational numbers. This is because they can be expressed as fractions.

For example, 2 can be rewritten as 2/1, or 200/100. -6 can be rewritten as -6/1, 6/-1, or -12/2.

Many non-integer, or decimal numbers, are also rational numbers.

For instance, 8.75 can be rewritten as 8 3/4, 875/100, or 1750/200. This also includes repeating decimal numbers like 0.3333333..., which can be rewritten as 1/3.

Related Tech Terms:

• Irrational Number Definition
• Natural Number Definition
• Integer Definition
• Floating Point Definition

In the metric system, yotta is a prefix for 1 septillion, or 10²⁴. So in some cases, a yottabyte is defined as 1 septillion, or 1,000,000,000,000,000,000,000,000 bytes.

But because computers work in binary, computer scientists usually define a yottabyte as 1,208,925,819,614,629,174,706,176 (1024⁸ or 2⁸⁰) bytes. This works out to 1,024 zettabytes.

The abbreviation for yottabyte is YB in both the metric system (1,000,000,000,000,000,000,000,000 bytes) and the binary system (1,208,925,819,614,629,174,706,176 bytes).

Some groups have proposed the name yobibyte for a unit of 1,208,925,819,614,629,174,706,176 bytes to prevent confusion. The abbreviation for yobibyte is YiB.

Related Tech Terms:

• Bit Definition
• Byte Definition
• Kilobyte Definition
• Megabyte Definition
• Gigabyte Definition
• Terabyte Definition
• Petabyte Definition
• Exabyte Definition
• Zettabyte Definition

In the metric system, zetta is a prefix for 1 sextillion, or 10²¹. So in some cases, a zettabyte is defined as 1 sextillion, or 1,000,000,000,000,000,000,000 bytes.

But because computers work in binary, computer scientists usually define a zettabyte as 1,180,591,620,717,411,303,424 (1024⁷ or 2⁷⁰) bytes. This works out to 1,024 exabytes.

The abbreviation for zettabyte is ZB in both the metric system (1,000,000,000,000,000,000,000 bytes) and the binary system (1,180,591,620,717,411,303,424 bytes).

Some groups have proposed the name zebibyte for a unit of 1,180,591,620,717,411,303,424 bytes to prevent confusion. The abbreviation for zebibyte is ZiB.

Related Tech Terms:

• Bit Definition
• Byte Definition
• Kilobyte Definition
• Megabyte Definition
• Gigabyte Definition
• Terabyte Definition
• Petabyte Definition
• Exabyte Definition
• Yottabyte Definition

In the metric system, exa is a prefix for 1 quintillion, or 10¹⁸. So in some cases, an exabyte is defined as 1 quintillion, or 1,000,000,000,000,000,000 bytes.

But because computers work in binary, computer scientists usually define a petabyte as 1,152,921,504,606,846,976 (1024⁶ or 2⁶⁰) bytes. This works out to 1,024 petabytes.

The abbreviation for exabyte is EB in both the metric system (1,000,000,000,000,000,000 bytes) and the binary system (1,152,921,504,606,846,976 bytes).

Some groups have proposed the name exbibyte for a unit of 1,152,921,504,606,846,976 bytes to prevent confusion. The abbreviation for exbibyte is EiB.

Related Tech Terms:

• Bit Definition
• Byte Definition
• Kilobyte Definition
• Megabyte Definition
• Gigabyte Definition
• Terabyte Definition
• Petabyte Definition
• Zettabyte Definition
• Yottabyte Definition