On a basic calculator, the keys that start with M, such as M+ and M-, are memory keys that allow users to store and modify a number in the device's memory.

Calculators convert input values into a form of scientific notation—a fixed set of digits with a decimal multiplied by a base to some exponent—to store and process very large or very small quantities efficiently at the cost of rounding errors.

The Model K—named for its construction on a kitchen table—was the first electromechanical digital binary adder, which used an electric circuit to provide the sum of a pair of zeroes and ones in binary.

Slide rules—ruler-sized mechanical calculators with a component that slides out to show relationships between numbers—were used by engineers at NASA during the Apollo missions.

View a library of custom programs that can be loaded onto graphing calculators, including productivity tools, reference materials, games, and interactive applications, such as prom proposals.

Unsatisfied with the designs provided by an Apple engineer, Steve Jobs designed the original Mac calculator in about 10 minutes.

See how computer memory really works—from binary bits to modern RAM

The video explains how computers store information as 1s and 0s, how RAM functions as fast working memory, and why systems utilize different types of storage. The video demonstrates how this process enables computers to operate.

Abaci, the plural of abacus, allowed individuals to perform arithmetic and tally quantities by moving pebbles called calculi, from which the word 'calculator' is derived.

One of the first mechanical calculators—the Pascaline—was built in the 1640s by French mathematician Blaise Pascal to help his father, who worked as a tax collector.

Try counting like the Maya in this interactive math game

The Maya numerical system used dots for 1, bars for 5, and a shell symbol for zero. This interactive resource lets users practice counting with the Maya base-20 system using the same symbols once common in the Yucatán.

Designed in 1937 by Harvard graduate student Howard H. Aiken, the 'Harvard Calculator' was used by the US Navy to solve advanced physics problems.

Various types of memory, each serving unique functions, create a complex brain system

These forms of memory, which can overlap in daily life, have been sorted into broad categories, such as short-term and long-term memory, and subtypes such as implicit memory, which uses saved information without conscious awareness that it’s being recalled.

Among the smallest mass-produced mechanical calculators in history, the Curta was designed by Austrian engineer Curt Herzstark while imprisoned in a Nazi concentration camp during World War II.

How to remember everything

On average, people can remember seven different things using their working memory. To better retain all the things we need to remember, Tiago Forte developed the Second Brain method: a simple approach for immediately capturing, organizing, and storing the myriad tasks, learnings, and resources we collect throughout the day.

Short-term memory is a temporary space for limited, newly learned information

Short-term memory stores info for 15 to 30 seconds and is managed by the prefrontal cortex. Though they're often confused, short-term memory stores information, while working memory actively uses it to help you reason, learn, and solve problems, such as a math equation.

Graphic processing units rely on a hierarchy of memory for optimization, where the smallest, fastest memory—registers—is located closest to the core and provides access to data in a fraction of a nanosecond.

As of 2025, the College Board has banned the use of calculators with computer algebra systems on the SAT and PSAT.

A history of manicules, or the little hands in books and posters

Manicules are illustrated hands used in many contexts to point something out, whether by medieval readers to highlight passages or in 19th-century advertising. The hands have a quirky, persistent history, showing up over hundreds of years in everything from Petrarch's books to computer cursors and the US Postal Service's "Return to Sender" stamp.

Memory exists as multiple types stored across various brain systems

Memory isn't one uniform function—it's made up of multiple systems, like declarative (facts/events) and non-declarative (skills/habits), which involve different brain areas such as the hippocampus, amygdala, and cerebellum.

How does muscle memory work?

Muscle memory is less about remembering how to ride a bike and more about what's happening in muscle cells. Increasing the cells' size, say by working out, leads to an increase in nuclei, which increases the production of mitochondria. When your fitness regimen falls to the wayside and you decide to re-enter the gym, these gains-based nuclei are already present to quicken muscle cells' adaptation to exercise.

Retrieval cues trigger memories and emotions from long-term storage

Retrieval cues can activate specific cells in a neural network, creating a cascade of neurons that collectively make up a memory. Specific cues help regulate emotions during stress by activating positive memories.

A 14-year-old "human calculator" shatters six mathematical world records in one day

A teenage prodigy from Maharashtra, India named Aaryan Shukla set the record for the fastest time to mentally add 50 five-digit numbers. He did so in just 25.19 seconds–roughly equivalent to one addition every 0.5 seconds. The math whiz said he practices calculations for around five to six hours a day.

Logic gates—digital versions of conditional statements, such as 'if 0 and 1, then 1'—are specialized circuits that combine multiple digital signals, like the binary code representing numbers, into a single output, thereby allowing machines to perform math.

Transistors are the foundational components of integrated circuits and microchips and manage the processing of electronic signals by controlling the flow of electricity.

How do touchscreens work?

Touchscreens have revolutionized digital interactions, but how they work widely varies depending on the device. Explore the history and workings of the most common types—capacitive and resistive—and new interaction methods incorporated into foldable screens and touchless interfaces.

Microchips in payment cards improve security by generating unique transaction codes

Magnetic strips store unchanging data that is easily cloned, but microchips act as miniature computers that encrypt sensitive data. They also resist fraud by creating data unique to each transaction, preventing duplication.

Researchers use the brain's ability to edit memories to explore memory deletion

Scientists have successfully implanted false memories in mice after studying how the editing process works in the brain. Beyond potentially deleting memories in those with PTSD, upcoming research may allow clinicians to forecast the onset of neurodegenerative diseases.

The first commercially successful calculating machine—the arithmometer—was patented in 1820 but not mass-produced for over three decades, likely because its inventor was focused on his insurance business.

Learn the differences between mild cognitive impairment and age-associated memory loss

Mild cognitive impairment is a condition in which people experience more thinking and memory problems than expected for their age. It's often associated with depression and anxiety. Daily routines, writing things down, and healthy lifestyle choices can help cope with the condition, but there's no cure. The condition elevates the risk of developing dementia and Alzheimer's.

Master the banking basics

Before deciding on a credit union, it’s important that you understand the basics. That way you can know exactly what’s happening with your hard-earned money behind the scenes. Flip through these flashcards to make sure you understand key terms like “deposit” and “checking account.” Then, you can read up on top banking products and start to find a credit union that works for you. Click here, then scroll down the page to find the cards.

Turing machines consist of an infinite tape, a read-write mechanism and instructions

Based on the information the mechanism reads on the tape, the machine follows the applicable instruction (e.g., if you read a 1, write a 0) and may proceed to the next cell of data. Given enough time and memory, Alan Turing proposed such a machine could perform any computation.

A battery management system determines the displayed battery percentage

The software in modern devices provides values by combining estimates based on voltage—akin to knowing how much air is left in a tire based on the pressure of the escaping air—and coulomb counting, where the rate of electrical current is calibrated to the ratio of remaining charge to full capacity.

Sensory memory is information collected from your senses

Lasting seconds before moving into short-term memory or being forgotten, sensory memory aids in environmental awareness and navigation. Key brain regions involved include auditory, somatosensory, gustatory, visual, and olfactory cortices.

VisiCalc was the first electronic spreadsheet, released with Apple II's personal computer in 1979

Before 1979, managers were essentially information processors working off paper ledgers. Scenario modeling was slow, manual, and expensive. Companies were understood as organizations that built things with financial analysis as secondary. VisiCalc made calculation so cheap that you could work iteratively, setting out forecasts and tweaking assumptions until you got the answer you wanted. Oks argues It created a new way of seeing the world.

Build atoms to learn about atomic number, mass number, and charge notations

In this simulation, users can add protons, neutrons, and electrons to create atoms, view their stability and atomic configurations, and identify how the amounts of these subatomic particles are detailed around the abbreviation for the resulting element using AZE notation.

An explanation of Turing machines—the foundations of digital algorithms and computers

The device reads data, overwrites or ignores it, and then moves on to the next piece of data based on a set of programmed rules. By imagining this data as zeros and ones—binary that makes up computer code—Turing machines became the theoretical models for how any algorithm could be run on a computer if the procedure could be coded into a set of digital rules.

Modern Monetary Theory 101

Modern Monetary Theory is a macroeconomic theory that says government spending should not be restrained by fears of rising debt. Here's a breakdown of how the theory works.

Most advanced touch screens rely on electrical charge in your skin

Capacitive touch screens store electrical charges in an electrostatic grid of tiny wires. When we touch the screen a tiny electrical charge is transferred from the screen to the finger to complete a circuit (since skin has positive and negative charges). This connection creates a voltage drop on that point of the screen. Cloth, however, doesn't conduct electricity, which is why humans can't wear thick gloves and operate their smartphones.

Semiconductor chips are electronic devices that store and process information

They can contain billions of microscopic switches on a chip smaller than a fingernail. An article provides a quick overview of how the devices work and how they’ve provided the backbone of the computer age.

Consistency and emotional engagement can improve the formation of memories

While sleep lets the brain re-trigger neurons associated with our experiences to cement them in long-term memory, repeating actions, like storing one's keys in the same location, can mimic these benefits. Emotionally charged memories are often ruminated upon, improving their future recall.

Microsoft Excel is used by over a billion people worldwide

The upstart computer software company Microsoft launched its columns-and-rows spreadsheet program in 1985, enabling users to sort information, create charts, and perform calculations with minimal friction. It would be coupled with Microsoft Word and PowerPoint in 1990 as part of the Microsoft Office for Windows.

Many investment bankers work on mergers and acquisitions

At some point in their careers, many investment bankers work on facilitating or advising clients on mergers or acquisitions. From analyzing industry group trends to deal negotiations, an M&A in investment banking explainer outlines how investment bankers handle these business transactions.

Try out an emulated version of the TI-84 Plus CE, the graphing calculator released by Texas Instruments in 2015.

Use a CD rate calculator

This CD Rate Calculator allows you to determine your interest earnings and total savings balance at CD maturity. Enter your initial deposit, your interest rate, and your term length in months or years. Click here to use it.

The magnetic constant sets the strength of magnetic fields

The permeability of free space, or μ₀, contributes to the speed of light in the universe—a fundamental constant. It also helps quantify how the movement of electric charges generates a magnetic field and vice versa.

What is the function of money?

Nearly everyone uses some form of money to facilitate day-to-day activities, but what is it, anyways? Economists define money as anything that can be accepted as final payment for goods and services. Shells, beads, corn, and a wide range of objects have acted as money throughout history—explore the common but deceptively abstract concept of money in this eight-minute podcast from the Federal Reserve.

CRISPR-Cas systems act as genetic memory banks for defending bacterial cells

When viruses called phages inject DNA into bacteria, some bacterial species store bits of this DNA in their own genomes. This allows them to recognize and destroy the same virus if it attacks again.

Mathematicians often solve problems using wordless mental processes

It's a common technique among expert mathematicians, where thinkers rely on intuition, blurry perceptions and subconscious work—no writing, no formulas. The state is distinct from daydreaming, and often relies on sudden illuminations stemming from extended periods of subconscious reflection.

All computers are defined by their ability to input, store, process, and output data

From wooden machines to wearable tech, computers have changed a lot in appearance, but they all still perform the same essential tasks. Early computers were made of wood and metal—some were so big that they filled entire rooms just to solve simple math problems.

A smartphone contains over a dozen rare earth elements

One of the most important elements is indium, which makes up an electrically-conductive mesh beneath the display that provides touchscreen functionality. Alloys containing REEs are used in the magnets needed for the microphone and speaker.

On credit and debit cards, magnetic stripes have been slowly replaced by microchips that use dynamic, encrypted data to prevent card cloning and counterfeit fraud.