Lecture Notes for Operating Systems

Clocks and Terminals, 25 October 2000

1. Clocks - an odd divice

   1. line or crystal clocks

   2. one-shot or periodic; countdown or up; square-wave or repetitive, clock ticks

   3. time - utc (coordinated universal time), formerly gmt (greenwich mean time); ntp

   4. the clock driver

      1. time of day - resolution, precision, time 0

      2. accounting information - debugging, billing, statistics

      3. wakeup signals - quantum, keep-alive, heartbeats

2. Terminals

   1. hardware

      1. memory mapped - video controllers, character or pixel based

      2. serial line - rs232, uarts

      3. network terminals - x terms, sunray; servers, clients

   2. software

      1. buffering - speed disparities

      2. key mapping

      3. character processing - control-h, newlines, raw, cooked;

      4. output - interrupt driven; scrolling; special characters, bell, form feed; cursors; escape sequences

3. unix streams

   1. serial-line devices; extended to networking

   2. system 5 unix systems

   3. stream module - four message queues and a box; internal queues; up stream, down stream

   4. stream messages - data and control parts; priority

   5. streams device - stream head, stream end or device, push and pop modules in between

This page last modified on 25 October 2000.