The first electronic computer was built in the 1940s, but the story of computing machines goes back centuries

The answer depends on what you mean by "computer." If you mean a machine that could perform calculations automatically, the earliest versions date to the 1600s. If you mean an electronic digital computer — the kind that uses electricity and processes information as ones and zeros — that arrived in the 1940s. The first general-purpose electronic computer, called ENIAC, was completed in 1946 at the University of Pennsylvania. It weighed 30 tons, filled a room, and used 18,000 vacuum tubes instead of the transistors and chips in modern computers.

The computers you use today — laptops, desktops, phones — are descendants of machines built in the 1960s and 1970s. The first personal computer sold to the public was the Altair 8800 in 1975. Apple released the Apple II in 1977, and IBM released the IBM PC in 1981. These machines were still expensive and required technical knowledge to operate, but they marked the shift from computers as room-sized industrial tools to devices individuals could own and use at home.

Key Takeaways

  • ENIAC, completed in 1946, was the first general-purpose electronic computer and used vacuum tubes to process information.
  • The Altair 8800 (1975), Apple II (1977), and IBM PC (1981) were the first computers designed for individual users rather than large institutions.
  • Mechanical calculating machines existed for centuries before electronic computers, including the abacus, the slide rule, and Babbage's Analytical Engine in the 1800s.
  • The invention of the transistor in 1947 and the integrated circuit in 1958 made computers smaller, faster, and affordable enough for homes and offices.

Mechanical calculating machines: the ancestors of the computer

Long before electricity, people built machines to perform arithmetic. The abacus, used in ancient Mesopotamia and China, was a frame with beads on rods that allowed users to count and calculate by moving the beads. It was not automatic — a person had to operate it — but it was the first tool designed specifically to make math faster.

In the 1600s, mathematicians and inventors began building mechanical devices that could add and subtract without human intervention. Wilhelm Schickard in Germany and Blaise Pascal in France both designed calculating machines in the 1600s. In the 1800s, Charles Babbage designed the Analytical Engine, a machine that could be programmed using punched cards and could perform any mathematical operation. Babbage's machine was never fully built during his lifetime, but his design contained the core ideas that would later define electronic computers: a memory to store numbers, a processor to perform operations, and a way to input instructions.

These mechanical machines were limited by their design. They could only perform one task at a time, they were prone to breaking, and they required someone to turn a crank or press a key for each operation. They were useful for banks, insurance companies, and scientists, but they were not what we would call computers today.

The vacuum tube era: ENIAC and the first electronic computers

The invention of the vacuum tube in the early 1900s changed everything. A vacuum tube is a glass bulb with electrodes inside that can switch on and off very quickly using electricity. This meant a machine could perform calculations at electronic speed — thousands of times faster than mechanical gears.

During World War II, the U.S. military needed to calculate ballistic tables for artillery. In 1943, the Army contracted with the University of Pennsylvania to build a machine to do this work. The result was ENIAC (Electronic Numerical Integrator and Computer), completed in 1946. ENIAC could add two numbers in 200 microseconds — a speed that seemed miraculous at the time. It was programmed by hand, using cables and switches, and it generated so much heat that it required its own air-conditioning system.

ENIAC proved that electronic computing was possible, but it was not practical for everyday use. It cost $500,000, required a team of technicians to operate, and broke down frequently. Other universities and governments built similar machines in the late 1940s and 1950s, including UNIVAC, which was the first computer sold commercially. These early computers filled entire rooms and were owned only by large institutions.

The transistor and the shrinking computer

In 1947, scientists at Bell Labs invented the transistor, a tiny device that could do the same job as a vacuum tube but was much smaller, used less electricity, and generated less heat. Transistors were made from semiconductor materials like silicon, and they could be manufactured in large quantities.

Computers built with transistors were smaller and more reliable than vacuum-tube machines. In the 1950s and 1960s, transistor computers became common in universities, government agencies, and large corporations. They still cost tens of thousands of dollars and required special rooms and trained operators, but they were a major step toward computers that ordinary people could use.

The next breakthrough came in 1958 when engineers invented the integrated circuit — a way to put many transistors on a single chip of silicon. Integrated circuits made computers even smaller and cheaper. By the 1970s, computers small enough to fit on a desktop were possible.

Personal computers arrive: the 1970s and 1980s

The first computers designed for individual users appeared in the mid-1970s. The Altair 8800, released in 1975, cost $395 and came as a kit that hobbyists had to assemble themselves. It had no screen or keyboard — you entered data using switches and read results from blinking lights. Despite these limitations, it sold thousands of units and sparked the personal computer revolution.

In 1977, Apple Computer released the Apple II, the first computer with a color screen and a keyboard that looked and worked somewhat like modern computers. It cost $1,298 and was aimed at small businesses and educated consumers. The Apple II was a commercial success and established Apple as a major computer maker.

In 1981, IBM released the IBM PC, which used an operating system called MS-DOS. The IBM PC was expensive and not as user-friendly as the Apple II, but IBM's reputation and the decision to let other companies manufacture compatible machines made the IBM PC the standard for business computing. By the mid-1980s, personal computers were common in offices and homes.

From desktop to laptop to smartphone

Throughout the 1980s and 1990s, personal computers became faster, cheaper, and easier to use. The graphical user interface — the windows, icons, and mouse-based system that Apple pioneered and Microsoft copied — made computers accessible to people without technical training. The invention of the hard drive and the floppy disk allowed users to store large amounts of data.

Laptops appeared in the 1980s but were expensive and slow. By the 2000s, laptops became powerful enough to replace desktop computers for most users. The invention of the internet and the World Wide Web in the 1990s transformed computers from isolated machines into tools for communication and information access.

The smartphone, which is a computer in your pocket, arrived in the 2000s. The iPhone, released by Apple in 2007, was not the first smartphone, but it was the first to be widely adopted by ordinary people. Today, more people access the internet and perform computing tasks on smartphones than on traditional computers.

Why the date matters: what counts as a computer

The question "when was the computer made" does not have a single answer because the computer evolved gradually. If you count mechanical calculating machines, the computer was invented in the 1600s. If you count electronic machines, it was invented in the 1940s. If you count machines that ordinary people could own and use, it was invented in the 1970s.

What all these machines have in common is that they process information automatically according to instructions. A calculator that you have to press buttons on is not a computer — it is a tool. A machine that follows a program and produces results without human intervention for each step is a computer. By that definition, ENIAC was the first true computer, but Babbage's Analytical Engine, which was never built, had all the necessary parts.

Frequently Asked Questions

Who invented the computer?

No single person invented the computer. Charles Babbage designed the first programmable machine in the 1800s. John Atanasoff and Clifford Berry built the first electronic digital computer in 1939. John Mauchly and J. Presper Eckert led the team that built ENIAC in 1946. Many other engineers and scientists contributed to the development of computers over centuries.

What was the first computer used for?

ENIAC was built to calculate ballistic tables for the U.S. Army during World War II. After the war, it was used for scientific research, including calculations for the hydrogen bomb. Early computers were used by governments, universities, and large corporations for tasks that required millions of calculations, such as weather prediction and census data processing.

How much did the first personal computers cost?

The Altair 8800 kit cost $395 in 1975. The Apple II cost $1,298 in 1977. The IBM PC cost around $1,565 in 1981. These prices made personal computers affordable for small businesses and wealthy individuals, but not for most households until the 1990s, when prices fell significantly.

When did computers become common in homes?

Personal computers began appearing in homes in the early 1980s, but they were still expensive and required technical knowledge. By the mid-1990s, as prices fell and the internet became popular, computers became common household items. Today, most homes have multiple computing devices, including computers, tablets, and smartphones.

What is the difference between a computer and a calculator?

A calculator performs one operation at a time based on input from a user. A computer follows a program — a set of instructions — and can perform millions of operations without user input between steps. A computer can store data, make decisions based on that data, and produce complex results. A calculator is a tool; a computer is a programmable machine.