1950 to 1959: Starting the Ascent of Digital Computers and Software - The Technical and Social History of Software Engineering - page 92

Another important invention occurred in 1953 when engineers at IBM's San
Jose research facility created the first disk drive, which allowed random access
to data instead of sequential access, which was normally provided by tape drives.
The first commercial disk drive was the IBM RAMAC 350 in 1956. Without disk
drives and random access to data, computers would have very limited functional-
ity and later database technologies would not have occurred.
In 1953, IBM released the 650, which was aimed squarely at business custom-
ers (the earlier 701 was designed for science and defense customers). The IBM 650
was a market success and between the initial release and 1963, more than 2,000
were sold.
The IBM 650 featured a rotating magnetic drum for memory. Programmers had
to be sensitive to drum rotation speed to optimize performance. If a read instruc-
tion missed a piece of data, the next opportunity would not occur until the data
rotated under the read head again. There was also a small amount of magnetic core
memory, used as a buffer between the drum and the processing unit.
For external storage, at first the IBM 650 used only punch cards, but later tape
drives were added. Disks were not used in the IBM 650. After RAMAC was in-
vented, disk drives would be added to the later versions of the IBM 650.
One reason for the market success of the IBM 650 was because it was
backward-compatible with IBM's punch-card calculating machines. For example,
an output deck of cards from an IBM 650 computer could be printed on an earlier
IBM 402 accounting machine.
The early versions of the IBM 650 were programmed in machine language. But
in 1954, Stan Poley of IBM's T. J. Watson Research Center added the Symbol-
ic Optimal Assembly Program (SOAP). Eventually, more than a dozen program-
ming languages would become available for the IBM 650, including FORTRAN
in 1957.
Before the IBM 650, universities had built a number of computers, but they
were used only for a limited range of scientific studies and had no connection
to day-to-day university tasks. The IBM 650 started a trend of using digital
computers for academic business activities as well as research tools. Columbia
University, for example, would later have about 200 users of their IBM 650 com-
puters.