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.TITLE Erlang Program
.SUBTITLE B.#Z.#Lederman
.PARAGRAPH
The ERLANG program provides solutions to various trunking problems
using the Erlang blocking formulas.
.PARAGRAPH
The program when first started will prompt with "Enter#Wanted#Factor"
followed by a list of the unknown factors for which the program can
find a value, as listed below. Type in the name of one of these
factors as it appears in upper case. The program will then prompt for
the values required to calculate the desired answer. The data is
entered as follows:
.LIST
.LE; NUMBER OF TRUNKS: this is an integer (whole number), greater than
zero, entered with NO decimal point. This term is synonymous with the
general term "servers".
.LE; BLOCKING: this is a real number, expressed as a percentage
between 0.0 and 100.0 percent, entered WITH a decimal point. If no
decimal point is entered, two decimals are assumed.
.LE; TRAFFIC: this is the traffic on the group of servers in Erlangs.
It is a real number, entered with a decimal point.
.LE; PROBABILITIES are printed out as real numbers between zero and
one. They may be converted to percentages of time occupied by
multiplying by 100.
.END LIST.BLANK
When more than one value is to be entered, seperate the values with
commas. The program will then type out the entered data and the
calculated answer. It will then ask if you want to perform another
calculation of this type: entering "Y" will repeat the prompt for
input, otherwise the program will ask if you want to perform another
type of calculation. Answering "Y" will cause the
"Enter#Wanted#Factor" prompt to be repeated, otherwise the program
exits. Responding to a prompt with a "Control-Z" will also terminate
the program.
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Types of problems.
.LIST
.LE; BLOCKING: The number of trunks (servers) present and the amount
of traffic in Erlangs presented to these trunks is entered, and the
resulting percentage of traffic blocked is calculated.
.LE; TRUNKS: the traffic in Erlangs to be presented and the desired
blocking is entered, and the result is the number of trunks (servers)
required for the required blocking to not be exceeded.
.LE; INPUT: The traffic received over a group of trunks (servers) and
the number of trunks is entered. The program calculates the amount of
traffic which must have been presented at the far end of the trunk
bundle, and the blocking observed at the far end for the given amount
of traffic to have been received.
.LE; TRAFFIC: The number of trunks (servers) and the percentage of
blocking which may be tolerated is entered. The result is the amount
of traffic which may be presented to that number of trunks for that
amount of blocking not to be exceeded.
.LE; QUEUE: The number of trunks and the traffic in Erlangs presented
to those trunks is entered. The result is the probability of delay in
service (P>0) for a queueing system.
.LE; PROB(ability): only the first four letters are entered. The
program will prompt for one of three calculations:
.LIST
.LE; SINGLE: The amount of traffic in Erlangs and the number of trunks
(servers) is entered. The program will list the probability of exactly
that number of trunks being occupied: this is identical to the amount
of time during the observation period that that number of trunks will
be occupied.
.LE; AVERAGE: The amount of traffic in Erlangs is entered, and the
program will list the mean number of trunks occupied, and the standard
deviation to the mean, for that amount of traffic on an unlimited
number of trunks (servers).
.LE; TABLE: The amount of traffic in Erlangs is entered, and the
program will list a table showing the probabilities that at any
instant in time no trunks are occupied, one trunk is occupied, two
trunks are occupied, etc. If a full table is requested, the table is
printed until the cumulative probability (the probability that that
number of trunks or fewer trunks are occupied) is effectivly equal to
one (all practical cases have been considered). Otherwise, the program
prompts for a starting and ending number of trunks, and the table is
printed out between these limits.
.END LIST
.END LIST