Extensions
INITs evolved into system extensions, gaining additional ad hoc protocols along the way, such as supplying an icon to be displayed at boot time (origin of this was ShowINIT). The 'parade of puzzle pieces and icons' across the screen as each extension loaded became familiar to all Mac users. Apple themselves eventually released major (but optional) pieces of the operating system as extensions, such as QuickTime, QuickDraw 3D and many others. A substantial amount of services and drivers in Mac OS—both official and third party—were provided as extensions, allowing for the OS to be trimmed down by disabling them.
System extensions were a common source of instability on the Macintosh, as third-party code was of variable quality and would often patch the system in ways that did not always work correctly. In addition different extensions might try to patch the same part of the system, which could lead to extension conflicts and other instability. Tracking down these sources of trouble was another task most Mac users encountered at some point.
The simplest way to clean-boot the operating system was to hold the shift key: loading of extensions would be bypassed. System 7.5 added the Extensions Manager, which allowed the user to quickly enable or disable particular extensions, and also to define sets of them that would work correctly together. Extensions Manager came with two read-only base sets provided: one that contained the subset of extensions needed for basic OS operation, and one that enabled all the official extensions that shipped with the OS but disabled all third-party extensions.
The loading order of extensions was a side-effect of the GetFInfo function that was used by the loader to enumerate the files in the Extension folder. While Apple always have said that the order that results from enumeration of files using this function is undefined, on HFS volumes this function enumerated files in the order stored in the HFS catalog. People figured out that changing the first character in the file name could change the extension loading order, which caused trouble when Mac OS 8.1 moved to HFS+. Apple ended up having to change the loader to manually sort the filenames returned by this function into a table, and provided an interface to allow software to manually change the table.
Read more about this topic: Extension (Mac OS)
Famous quotes containing the word extensions:
“If we focus exclusively on teaching our children to read, write, spell, and count in their first years of life, we turn our homes into extensions of school and turn bringing up a child into an exercise in curriculum development. We should be parents first and teachers of academic skills second.”
—Neil Kurshan (20th century)
“The psychological umbilical cord is more difficult to cut than the real one. We experience our children as extensions of ourselves, and we feel as though their behavior is an expression of something within us...instead of an expression of something in them. We see in our children our own reflection, and when we don’t like what we see, we feel angry at the reflection.”
—Elaine Heffner (20th century)