The First Computers Were Built in the 1940s, Not Earlier

The first true electronic computer was the ENIAC (Electronic Numerical Integrator and Computer), completed in 1946 at the University of Pennsylvania. It weighed 30 tons, filled an entire room, and used 18,000 vacuum tubes instead of transistors or chips. ENIAC could perform 5,000 additions per second—fast for its time, but slower than a modern phone calculator.

Before ENIAC, machines that could calculate existed, but they were not computers in the modern sense. A mechanical adding machine or a slide rule could perform math, but it could not store instructions, change what it did based on the result of a calculation, or run a program. ENIAC could do all three, which is why it marks the real beginning of computing.

The British built the Colossus computer in 1943 to break German military codes during World War II, making it technically the first electronic computer to run. However, Colossus was designed for one specific task and could not be reprogrammed for other work. ENIAC was the first general-purpose electronic computer—it could be rewired to solve different problems, which is why most histories credit it as the birth of modern computing.

Key Takeaways

  • ENIAC, completed in 1946, was the first general-purpose electronic computer and could store instructions and change its behavior based on calculations.
  • Colossus, built in Britain in 1943, was technically the first electronic computer to operate, but it could only perform one task and could not be reprogrammed.
  • Earlier machines like adding machines and slide rules could calculate but could not store programs or make decisions based on results, so they are not considered true computers.
  • The vacuum tube technology that powered early computers was replaced by transistors in the 1950s and 1960s, making machines smaller and more reliable.
  • Personal computers did not appear until the 1970s, decades after the first room-sized electronic machines.

Mechanical Calculators Came Before Electronic Computers

Machines that could perform arithmetic existed long before electronics. The Pascaline, invented by Blaise Pascal in 1642, used gears and wheels to add and subtract. In the 1800s, Charles Babbage designed the Analytical Engine, a mechanical device that could follow instructions written on punch cards and store intermediate results—ideas that directly influenced how modern computers work. However, Babbage never built a working version, and mechanical machines were too slow and unreliable for practical computing.

In the early 1900s, tabulating machines that used electricity and punch cards became common in offices and government agencies. Herman Hollerith's tabulating machine, used in the 1890 U.S. Census, could read holes punched in cards and count them electrically. These machines were fast for their time but still could not store programs or make logical decisions. They were tools for data processing, not computers.

The Transition from Vacuum Tubes to Transistors

ENIAC's vacuum tubes generated enormous heat and failed frequently. A single tube might last only a few hundred hours before burning out, and replacing one meant shutting down the entire machine. In 1947, Bell Labs invented the transistor, a tiny device that could do the same job as a vacuum tube but used far less power and lasted much longer.

The first transistor-based computer, the UNIVAC 1103, was completed in 1953. It was smaller and more reliable than ENIAC, though still room-sized. By the late 1950s, transistor computers became standard in universities and large corporations. The shift from tubes to transistors made computing faster, cheaper, and more practical for everyday use.

Integrated Circuits Made Computers Smaller and Faster

In 1958, Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor independently invented the integrated circuit—a way to put many transistors on a single chip of silicon. This breakthrough meant that computers no longer needed to be room-sized. By the mid-1960s, computers using integrated circuits were small enough to sit on a desk, though they still cost tens of thousands of dollars.

The Intel 4004, released in 1971, was the first microprocessor—a complete computer on a single chip. It had only 2,300 transistors and ran at 740 kilohertz, but it proved that powerful computing could fit in a small space. This invention made personal computers possible.

Personal Computers Arrived in the 1970s

The first computers that ordinary people could buy were the Altair 8800 (1975) and the Apple II (1977). The Altair was a kit that hobbyists had to assemble themselves; it had no keyboard or screen, only switches and lights. The Apple II came fully assembled with a keyboard and could connect to a television as a display, making it the first computer designed for home use.

The IBM Personal Computer, released in 1981, set the standard for office computers. It used the Intel 8086 processor and ran the MS-DOS operating system. IBM's design was copied by many manufacturers, creating the "IBM-compatible" computers that dominated offices and homes through the 1980s and 1990s.

From Mainframes to Laptops and Smartphones

In the 1980s and 1990s, computers became faster, cheaper, and more common. The graphical user interface—pioneered by Xerox Alto in 1973 but popularized by the Apple Macintosh in 1984—made computers easier to use for people without technical training. The rise of the internet in the 1990s connected computers together and changed how people worked and communicated.

Laptop computers became practical in the 1990s as batteries and displays improved. The first smartphones, like the iPhone released in 2007, put a computer in a pocket. Today, a smartphone has more computing power than ENIAC, uses less electricity, and costs a fraction of what early computers did. The basic principles that made ENIAC work—storing instructions, performing calculations, and making decisions based on results—remain the same.

Frequently Asked Questions

Did Charles Babbage invent the computer?

Babbage designed the Analytical Engine in the 1800s, which had many features of a modern computer, including the ability to follow instructions and store data. However, he never built a working version, and mechanical technology was too slow for practical computing. ENIAC, completed in 1946, was the first computer that actually ran.

Was the computer invented in America or Britain?

The first electronic computer to operate was Colossus, built in Britain in 1943. However, ENIAC, completed in the United States in 1946, was the first general-purpose computer that could be reprogrammed for different tasks. Both countries contributed to early computing development.

How much did the first computers cost?

ENIAC cost about $500,000 to build in 1946, which is roughly $8 million in today's money. Early personal computers in the 1970s cost $500 to $2,000. Today, you can buy a capable computer for under $300, and smartphones with more power cost $200 to $1,000.

How fast were the first computers compared to today?

ENIAC performed 5,000 additions per second. A modern laptop performs billions of operations per second. However, ENIAC was revolutionary for its time—it could solve complex math problems in hours that would take a human weeks to calculate by hand.