Glossary
API
The set of function calls in a library, along with their arguments and their semantics. APIs
are published so that programmers can always know which interface a vendor supports.
asynchronous signal
A signal that is sent to a process independently of what the process happens to be doing.
An asynchronous signal can arrive at any time whatsoever, with no relation to what the
program happens to be doing (cf. synchronous signal).
async I/O
An abbreviation for asynchronous input/output--normally, I/O calls block in the kernel
while waiting for data to come off a disk, a tape, or some other "slow" device. But async
I/O calls are designed not to block. Such calls return immediately, so the user can
continue to work. Whenever the data comes off the disk, the process will be sent a signal
to let it know the call has completed.
atomic operation
An operation that is guaranteed to take place "at a single time." No other operation can do
anything in the middle of an atomic operation that would change the result.
blocking system call
A system call that blocks in the kernel while it waits for something to happen. Disk reads
and reading from a terminal are typically blocking calls.
cache memory
A section of very fast (and expensive) memory that is located very close to the CPU. It is
an extra layer in the storage hierarchy and helps "well-behaved" programs run much
faster.
CDE
An abbreviation for common desktop environment--the specification for the look and feel
that the major UNIX vendors have adopted. CDE includes a set of desktop tools.
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