Kendall introduced the A/B/C type queueing notation in 1953. It has since been extended:
1. A code describing the arrival process. The codes used are:
2. A similar code representing the service process. The same symbols are used.
3. The Number of service channels.
4. The Priority order that jobs in the line served:
5. The maximum size of the system. The maximum number of customers allowed in the system including those in service. When the number is at this maximum, further arrivals are turned away.
6. The size of calling source. The size of the population from which the customers come. This limits the arrival rate. As more jobs queue up there are fewer available to arrive into the system.
The etymology is from the Latin coda, meaning tail.
Queueing theory is directly applicable to intelligent transportation systems, call centers, PABXs, network telecommunications, server queueing, mainframe computer queueing of telecommunications terminals, and advanced telecommunications systems.
See also: Little's law