Sets the total number of columns found in the user file for use with a bulk copy into or out of SQL Server.
This function can be called only after bcp_init has been called with a valid file name.
You should call this function only if you intend to use a user-file format that differs from the default. For more information about a description of the default user-file format, see bcp_init.
After calling bcp_columns, you must call bcp_colfmtfor each column in the user file to completely define a custom file format.