If you want to use a modem only for MS Windows/Dos, then you can just install almost any modem and it will work OK. With a Linux PC it's not usually this easy unless you use an external modem. All external modems should work OK (even if they are labeled "Plug and Play") But most new internal modems are Plug-and-Play (PnP) and have PnP serial ports. In some cases (depending both on the modem and your version of Linux) The PnP configuring is built into the serial driver so you don't need to do anything. If it's an ISA modem you may need to use the Linux "isapnp" program to configure it (but this is planned to be built into future drivers ??). See the Plug-and-Play-HOWTO and the isapnp docs for more information.
Since each modem has an associated serial port there are two parts to configuring a modem:
Most of the above configuring (but not necessarily most of the effort)
is done by the communication program that you use with the modem such
as minicom, seyon, wvdial (for PPP). If you use the
modem for dial-in, then the getty program which you use to
present outsiders with a login-prompt, will help configure. Thus to
configure the modem (and much of the serial port) you need to
configure the communication program (such as the PPP dialer
or getty).
Unfortunately the above configuring doesn't do the low-level configuring of the serial port: setting its IO address and IRQ in both the hardware and the driver. If you are lucky, this will happen automatically when you boot Linux. Setting these in the hardware was formerly done by jumpers but today it's done by "Plug-and-Play" software.
But there's a serious problem: Linux (as of late 1999) is not a Plug-and-Play operating system but it does have Plug-and-Play tools which you may use to set up the configuration although they are not always very user friendly. This may create a difficult problem for you. The next section will go into this in much more detail.