Editing DOS/360 and successors (section)

===Program libraries===
Executable programs were stored in a ''Core Image Library''. While running, DOS could not reclaim space as programs were deleted or replaced with newer versions. When the Core Image Library became full, it had to be compressed by a utility program, and this could halt development work until it was complete. Many shops simply froze changes for a day, compressed the CIL "off-line", and IPLed with the new Core Image Library at the beginning of a business day.  A ''relocatable library'' for linkable object programs and a ''source statement library'' for assembler macros and include text were also supported.  Installations could define additional ''private'' relocatable and source statement libraries on other disk volumes.