The transistor, invented at Bell Labs in 1947, was the defining technological advancement that characterized second-generation computers (roughly 1959-1965). It replaced the large, power-hungry, heat-generating, and fragile vacuum tubes found in first-generation machines. Transistors were significantly smaller, faster, more energy-efficient, more reliable, and less expensive to manufacture, leading to more practical and widespread use of computers. The integrated circuit (IC) came with the third generation, and the microprocessor later with the fourth. The magnetic drum was an early memory storage device, not a processing component that defined a generation like the others.

Magnetic bubble memory, developed in the 1960s, was an ingenious non-volatile memory technology that stored data as tiny magnetic domains (bubbles) in a thin film of magnetic material. It held promise for high-density storage and robustness without moving parts. However, its widespread adoption was ultimately thwarted by the rapid advancements and cost reductions in existing and emerging memory technologies. Hard disk drives (HDDs) offered significantly higher storage capacities at lower costs per bit, while semiconductor memory (like DRAM and SRAM) provided vastly superior access speeds and lower power consumption, becoming the dominant choice for volatile main memory. The combined evolution of these two technologies made bubble memory economically uncompetitive by the 1980s, despite its technical merits. Vacuum tubes were an early electronic component, largely obsolete by the time bubble memory was being developed. Punched cards were an even earlier form of data storage and input, completely unrelated in terms of technological competition. Magnetic core memory, while prevalent before and during the early development of bubble memory, was also largely superseded by semiconductor memory for main memory applications due to its higher cost, bulk, and slower speeds. Therefore, the combined progress in hard disk drives and semiconductor memory sealed the fate of magnetic bubble memory.

Built between 1937 and 1942 at Iowa State College, the ABC was designed to solve systems of linear equations. A 1973 court ruling declared it the first electronic digital computer, invalidating the patent for the ENIAC.

Magnetic core memory, which used tiny magnetic rings (cores) to store information, was faster and more reliable than magnetic drums and became the standard for computer memory during the second and third generations.

IBM contracted with a small company called Microsoft to provide the operating system for their PC. Microsoft purchased a system called QDOS, adapted it, and licensed it to IBM as PC-DOS, while retaining the right to sell it to other companies as MS-DOS.

The Xerox STAR 8010 Information System, launched commercially in 1981, holds the distinction of being the first computer system to offer a comprehensive graphical user interface (GUI). Its revolutionary design included a 'desktop' metaphor for file and application management, the ability to open, overlap, and resize multiple windows, interactive icons representing various documents and programs, and primary user interaction driven by a mouse. Although the Xerox STAR did not achieve widespread commercial success due to its high cost and target market (primarily large corporations), its pioneering GUI design had a profound and lasting impact on the computing industry. Both the Apple Lisa (1983) and the highly influential Apple Macintosh (1984) drew significant inspiration and adapted many core concepts from the Xerox STAR, subsequently popularizing the GUI for a broader consumer audience. The Commodore Amiga 1000, released in 1985, also featured an advanced graphical interface, but it followed the systems mentioned above. Therefore, while Apple systems like the Macintosh made GUIs commonplace, the Xerox STAR was the foundational commercial product to implement a full-fledged GUI.

Ada Lovelace, an English mathematician and writer, is celebrated for her work on Charles Babbage's proposed mechanical computer, the Analytical Engine. She wrote what is considered the first algorithm intended to be processed by a machine, making her the world's first computer programmer.

Researchers at Xerox's Palo Alto Research Center (PARC) in the 1970s developed many foundational technologies for personal computing, including the graphical user interface with its desktop metaphor, the computer mouse, and Ethernet networking.

The Von Neumann architecture, which forms the basis of nearly all modern computers, is the design concept of a stored-program computer where both program instructions and the data they operate on are held in the same memory space.

C was developed by Dennis Ritchie at Bell Labs between 1972 and 1973. It was created to re-implement the Unix operating system and has since become one of the most widely used programming languages of all time.