From the syntax manual entry for LOGISTIC REGRESSION, syntax template:

LOGISTIC REGRESSION [VARIABLES =] dependent var [WITH independent varlist [BY var [BY var] ... ]]

etc.

Later,

"· You can indicate an interaction term on the variable list by using the keyword BY to separate the individual variables."

I don't quite understand this. If you use "BY var", does that mean interaction terms between "var" and all preceding variables, or what? Or can specific interaction variables be included, or excluded, on VARIABLES or METHOD subcommands?