In the following description, local variables and arrays that are given the SAVE attribute are called static variables.
FTN95 presets the value of all static variables to zero. This is the case even when /ZEROISE is not applied. A related option /SAVE applies the SAVE attribute to all local variables and arrays.
/ZEROISE is provided for use with /UNDEF (and options such as /CHECKMATE that imply /UNDEF). Otherwise /ZEROISE has no impact on the code generated by FTN95.
When used together, /ZEROISE over-rides /UNDEF for static variables and presets these values to zero rather than the "undefined" state. /ZEROISE is provided for use with Win32 and .NET but not for x64.