History
Dynamic loading was a common technique for IBM/360 Operating systems (1960s to, the - still extant - Z/Architecture), particularly for I/O subroutines, and for COBOL and PL/1 runtime libraries. As far as the application programmer is concerned, the loading is largely transparent, since it is mostly handled by the operating system (or its I/O subsystem). The main advantages are:
- Fixes (patches) to the subsystems fixed all programs at once, without the need to relink them
- Libraries could be protected from unauthorized modification
IBM's strategic transaction processing system, CICS (1970s onwards) uses dynamic loading extensively both for its kernel and for normal application program loading. Corrections to application programs could be made offline and new copies of changed programs loaded dynamically without needing to restart CICS (that can, and frequently does, run 24/7).
Read more about this topic: Dynamic Loading
Famous quotes containing the word history:
“The history is always the same the product is always different and the history interests more than the product. More, that is, more. Yes. But if the product was not different the history which is the same would not be more interesting.”
—Gertrude Stein (1874–1946)
“It is the true office of history to represent the events themselves, together with the counsels, and to leave the observations and conclusions thereupon to the liberty and faculty of every man’s judgement.”
—Francis Bacon (1561–1626)
“What is most interesting and valuable in it, however, is not the materials for the history of Pontiac, or Braddock, or the Northwest, which it furnishes; not the annals of the country, but the natural facts, or perennials, which are ever without date. When out of history the truth shall be extracted, it will have shed its dates like withered leaves.”
—Henry David Thoreau (1817–1862)