The second generation of computers (1956–1963) is defined by the replacement of vacuum tubes with transistors. This shift made computers dramatically smaller, faster, cheaper, and more reliable than first-generation machines.
IBM's 7090 second-generation computer was used by NASA to track the trajectory of John Glenn's Friendship 7 spacecraft in 1962 — the first American to orbit Earth. The computers ran in real-time during the mission!
| Feature | Details |
|---|---|
| Period | 1956–1963 |
| Technology | Transistors (replaced vacuum tubes) |
| Language | Assembly language + early high-level (FORTRAN, COBOL) |
| Memory | Magnetic core memory |
| Storage | Magnetic tape and disks |
| Size | Smaller than 1st gen (room-sized → desk-sized) |
| Speed | Microseconds (faster than 1st gen's milliseconds) |
| Reliability | Higher — transistors don't burn out like tubes |
| Cost | Lower — but still very expensive |
The transistor (invented at Bell Labs, 1947) was the key innovation:
| Property | Vacuum Tube | Transistor |
|---|---|---|
| Size | Large (light bulb sized) | Tiny |
| Heat | Generates enormous heat | Minimal heat |
| Power | High power consumption | Low |
| Reliability | Fails frequently | Highly reliable |
| Speed | Slower | Faster |
A second-generation computer used thousands of transistors — each much smaller and faster than a vacuum tube.
| Generation | Period | Technology |
|---|---|---|
| 1st | 1940–1956 | Vacuum Tubes |
| 2nd | 1956–1963 | Transistors |
| 3rd | 1964–1971 | Integrated Circuits (ICs) |
| 4th | 1971–present | Microprocessors (VLSI) |
| 5th | Present+ | AI, Quantum Computing |
2nd generation computers used **Assembly Language** (symbolic codes instead of binary) and early high-level languages like **FORTRAN** (scientific computing, 1957) and **COBOL** (business computing, 1959).
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