Photo illustration by Lisa Larson-Walker. Photo by Bettmann/Getty Images.
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Future Tense
The Lines of Code That Changed Everything
Apollo 11, the JPEG, the first pop-up ad, and 33 other bits of software that have transformed our world.

Oct 14, 20198:00 PM

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Back in 2009, Facebook launched a world-changing piece of code—the “like” button. “Like” was the brainchild of several programmers and designers, including Leah Pearlman and Justin Rosenstein. They’d hypothesized that Facebook users were often too busy to leave comments on their friends’ posts—but if there were a simple button to push, boom: It would unlock a ton of uplifting affirmations. “Friends could validate each other with that much more frequency and ease,” as Pearlman later said.

It worked—maybe a little too well. By making “like” a frictionless gesture, by 2012 we’d mashed it more than 1 trillion times, and it really did unlock a flood of validation. But it had unsettling side effects, too. We’d post a photo, then sit there refreshing the page anxiously, waiting for the “likes” to increase. We’d wonder why someone else was getting more likes. So we began amping up the voltage in our daily online behavior: trying to be funnier, more caustic, more glamorous, more extreme.

Code shapes our lives. As the venture capitalist Marc Andreessen has written, “software is eating the world,” though at this point it’s probably more accurate to say software is digesting it.

Culturally, code exists in a nether zone. We can feel its gnostic effects on our everyday reality, but we rarely see it, and it’s quite inscrutable to non-initiates. (The folks in Silicon Valley like it that way; it helps them self-mythologize as wizards.) We construct top-10 lists for movies, games, TV—pieces of work that shape our souls. But we don’t sit around compiling lists of the world’s most consequential bits of code, even though they arguably inform the zeitgeist just as much.

So Slate decided to do precisely that. To shed light on the software that has tilted the world on its axis, the editors polled computer scientists, software developers, historians, policymakers, and journalists. They were asked to pick: Which pieces of code had a huge influence? Which ones warped our lives? About 75 responded with all sorts of ideas, and Slate has selected 36. It’s not a comprehensive list—it couldn’t be, given the massive welter of influential code that’s been written. (One fave of mine that didn’t make the cut: “Quicksort”! Or maybe Ada Lovelace’s Bernoulli algorithm.) Like all lists, it’s meant to provoke thought—to help us ponder anew how code undergirds our lives and how decisions made by programmers ripple into the future.

There’s code you’ve probably heard of, like HTML. Other code is powerful (like Monte Carlo simulations, which is used to model probabilities) but totally foreign to civilians. Some contain deadly mistakes, like the flaw in the Boeing 737 Max. And some are flat-out creepy, like the tracking pixel that lets marketers know whether you’ve opened an email.

One clear trend illustrated here: The most consequential code often creates new behaviors by removing friction. When software makes it easier to do something, we do more of it. The 1988 code that first created “Internet Relay Chat” allowed the denizens of the early internet to text-chat with one another in real time. Now real-time text is everywhere, from eye-glazingly infinite workplace Slack confabs to the riot of trolling and countertrolling in a Twitch livestream.

It’s not always clear at first when some code will become epoch-defining. Oftentimes it starts off as a weird experiment, a trial balloon. Back in 1961, Spacewar!, the first virally popular video game, might have seemed a pretty frivolous way to use a cabinet-size computer that cost, at the time, $120,000. (That’s more than $1 million in 2019 dollars.) But it pioneered many of the concepts that helped computers go mainstream: representing data as icons, allowing users to manipulate those icons with handheld controllers.

Code’s effects can surprise everyone, including the coders. —Clive Thompson, author of Coders: The Making of a New Tribe and the Remaking of the World
The Great Wall of China superimposed with #### code.
Photo illustration by Lisa Larson-Walker. Photo by Alex Adams/Getty Images.
Binary Punch Cards
Date: 1725
The first code

Binary programming long predates what we think of as computers. Basile Bouchon is believed to be the first person to punch holes into paper and use it to control a machine: In 1725, he invented a loom that wove its patterns based on the instructions provided in the perforated paper it was fed. A punched hole is the “one,” and the absence of a punched hole is the “zero.” As much as things have changed since then, the essential building block of code has not. —Elena Botella, Slate
The First Modern Code Executed
Date: 1948
Ushered in both the use of computer code and the computer models of nuclear devastation that shaped the Cold War arms race

The Electrical Numerical Integrator and Computer was the first programmable electronic computer. Completed in 1945, it was configured for each new problem by wiring connections between its many components. When one task, such as an addition, finished, a pulse triggered the next. But a few years later, Klára Dán von Neumann and Los Alamos scientist Nicholas Metropolis wired ENIAC to run the first modern code ever executed on any computer: hundreds of numerical instructions executed from an addressable read-only memory (ENIAC’s function table switches). They simulated the explosion of several atomic bomb designs being evaluated at Los Alamos National Lab in New Mexico, using the Monte Carlo technique by which a complex system is simulated, step by virtual step, to repeatedly map the probability distribution of possible outcomes. Von Neumann and Metropolis sent more than 20,000 cards back to the nuclear scientists at Los Alamos, tracing the progress of simulated neutrons through detonating warheads. The distant descendants of this code are still in use at Los Alamos today. —Thomas Haigh, co-author of ENIAC in Action: Making and Remaking the Modern Computer
Grace Hopper’s Compiler
Date: 1952
Made it possible for computers to process words

IF END OF DATA GO TO OPERATION 14 .

Wikipedia

Grace Hopper was programming an early computer when she decided to make the whole thing easier by rooting it in human language. Hopper, who enlisted in the US Naval Reserve during World War II, knew that people like her superiors in the military struggled to understand binary code. If programming languages could be English-based, the work would be less prone to errors and more accessible to those who didn’t have a Ph.D. in mathematics.

Some scoffed at the idea, but by the early 1950s she had devised a compiler—a set of instructions that converts a more intelligible kind of code to the lower-level code directly processed by the machine. With that tool, she and her lab developed FLOW-MATIC, the first programming language to incorporate English words based on that process. —Molly Olmstead, Slate
Spacewar!
Date: 1961
The first distributed video game

/ this routine handles a non-colliding ship invisibly
/ in hyperspace

hp1, dap hp2
count i ma1, hp2
law hp3 / next step
dac i ml1
law 7
dac i mb1
random
scr 9s
sir 9s
xct hr1
add i mx1
dac i mx1
swap
add i my1
dac i my1
random
scr 9s
sir 9s
xct hr2
dac i mdy
dio i mdx
setup .hpt,3
lac ran
dac i mth
hp4, lac i mth
sma
sub (311040
spa
add (311040
dac i mth
count .hpt,hp4
xct hd2
dac i ma1
hp2, jmp .

Steve Russell via Bitsavers.org

In late 1961 a group of young MIT employees, students, and associates (many of them members of the Tech Model Railroad Club) gained late-night access to a recently donated DEC PDP-1 computer. The leading edge of nonmilitary computing, the PDP-1 sold for $120,000 (that would be a bit more than $1 million today), featured 18-bit word length, and used paper tape for program storage. Over the course of five months, these programmers created a game in which two players control spaceships—the needle and the wedge—that engage in a one-on-one space battle while avoiding the gravity well of a star at center screen.

Spacewar! spread quickly across the early “hacker” community. It was later distributed by DEC with each PDP-1, preloaded in the core memory and ready to demonstrate when installed. The program significantly influenced the small coding community of the 1960s and inspired generations of video game creators. It lives on in emulations and is demonstrated regularly at the Computer History Museum on the last operational PDP-1. Steve Russell, the lead coder, said at a 2018 Smithsonian panel, “It’s more than 50 years old. There are no outstanding user complaints. There are no crash reports. And support is still available.”