The CHILDES database comes with the CLAN programs, which examine the data. The following list shows some of the more common CLAN programs:

• COMBO: Searches for items combined with Boolean operators like "and" or "or"
• FREQ: Establishes the frequency of searched items
• KWAL: Searches for key words and shows the utterance in which they occur
• MLU: Calculates the mean length of utterance

All of the programs have a common "syntax" for issuing commands. Minimally, include the name of the CLAN program and the name(s) of the file(s) for the program to examine. Hence, the following command means that MLU will calculate a mean length of utterance on Adam's file 55:

mlu adam55.cha

Although MLU would calculate the mean length of utterance, it would include the utterances of everybody in the file (Adam, Adam's mother, Paul, and Ursula). To concentrate only on Adam's utterances, use a CLAN switch to locate Adam's tiers present in the file. Hence the command below, which uses the CLAN switch called "+t", means that MLU will calculate a mean length of utterance on Adam's file 55 for only Adam's utterances (i.e., Adam's tier):

mlu +t*ADA adam55.cha

CLAN commands, therefore, must include the following elements in order:

1. Name of the program
2. Number of switches
3. Name of the file(s) to search

See Deconstructing CLAN Commands for more information on how to write CLAN commands.