The Second Generation, 1959-1964: The Transistor

The invention of the transistor, or semiconductor, was one of the most important developments leading to the personal computer revolution. Bell I aboratories engineers John Bardeen, Walter Brattain, and William Shockley invented the transistor in 1948. The transistor, which essentially functions ;is a solid-state electronic switch, replaced the much less suitable vacuum lube. The transistor revolutionized electronics in general and computer in particular. Not only did transistors shrink the size of the vacuum tube — but they also had numerous other advantages: they needed no warm-up lime, consumed less energy, and were faster and more reliable.

The conversion to transistors began the trend toward miniaturization that continues to this day. Today's small laptop (or palmtop) PC systems, which run on batteries, have more computing power than many earlier systems that filled rooms

During this generation, another important development was the move from machine language to assembly languages. Assembly languages use abbreviations for instructions (for example, "L" for "LOAD") rather than numbers. This made programming less cumbersome.

After the development of the symbolic languages came higher-level languages. In 1951, mathematician and naval officer Grace Murray Hoper conceived the first compiler program for translating from a higher-level language to the computer's machine language. The first language to receive widespread acceptance was FORTRAN (for FORmula TRANslator), developed in the mid-1950s as a scientific, mathematical and an engineering language. Higher-level languages allowed programmers to give more attention to solving problems. They no longer had to cope with all details of the machines themselves. Also in 1962 the first removable disc pack was marketed. Disc storage supplemented magnetic tape systems and enabled users to have fast access to desired data.

The rudiments of operating machines were also emerging. Loading programs loaded other programs into main memory from external media such as punched cards, paper tape, or magnetic tape. Monitor programs aided the programmer or computer operator to load other programs, monitor their execution, and examine the contents of memory locations. An input- output control systems consisted of a set of subroutines for manipulating input, output, and storage devices. By calling these subroutines, a program

could communicate with external devices without becoming involved in the intricacies of their internal operations.

All these new developments made the second generation of computers less costly to operate — and thus began a surge of growth in computer systems.