"A supercomputer is a device for turning compute-bound problems into I/O-bound problems." —Ken Batcher

A supercomputer is a computer that leads the world in terms of processing capacity, particularly speed of calculation, at the time of its introduction. The term Super Computing was first used by New York World newspaper in 1920 to refer to the large custom built tabulators IBM had made for Columbia University. Supercomputers introduced in the 1960s, designed primarily by Seymour Cray at Control Data Corporation (CDC), led the market into the 1970s until Cray left to form his own company, Cray Research. He then took over the supercomputer market with his new designs, all in all holding the top spot in supercomputing for 25 years (1965–1990). In the 1980s a large number of smaller competitors entered the market, in a parallel to the creation of the minicomputer market a decade earlier, but many of these disappeared in the mid-1990s "supercomputer market crash". Today, supercomputers are typically one-off custom designs produced by "traditional" companies such as IBM and HP, who had purchased many of the 1980s companies to gain their experience, although Cray Inc. still specializes in building supercomputers.

The term supercomputer itself is rather fluid, and today’s supercomputer tends to become tomorrow’s also-ran, as can be seen from the world’s first (non solid state) digital programmable electronic computer Colossus, used to break some German ciphers in World War II. CDC’s early machines were simply very fast single processors, some ten times the speed of the fastest machines offered by other companies. In the 1970s most supercomputers were dedicated to running a vector processor, and many of the newer players developed their own such processors at lower price points to enter the market. In the later 1980s and 1990s, attention turned from vector processors to massive parallel processing systems with thousands of simple CPUs; some being off the shelf units and others being custom designs. Today, parallel designs are based on "off the shelf" RISC microprocessors, such as the PowerPC or PA-RISC.