In most computers, a device is able to interrupt the main processor when it is ready for the next task. Once the processor is interrupted, it begins to execute the bottom half for that device. Code that interacts with a hardware device is called the device driver . The specific portion of the device driver that is responsible for responding to an interrupt is called the interrupt handler . In these notes, we attempt to build a network from the ground up.
Most computers have one or more serial ports.
A serial port can be connected via a serial line to another computer or to a hardware device. The serial port and serial line can communicate one data bit at a time in each direction, hence the name. Most serial ports can be configured to communicate at different speeds. In general, longer wires will only work with lower speeds, and shorter wires can support higher speeds. For two computers to communicate across the serial line, they have to configure their serial ports to run at the same speed.