To write new termcap descriptions, we recommend that you start by reading the terminal manufacturer's technical guide. That guide provides information for the eleven basic capabilities described in Eleven Basic Commands (see page Eleven Basic Commands) in this chapter. You must also have the terminal in front of you so that you can check the operation of the terminal as you are working on the termcap description. When you have included the eleven basic capabilities in the description, try the terminal to see if it works. Once you get it working, you can try adding additional features listed under Commands for Advanced Features.

If you have problems, first check to make sure that you entered the sequences from the guide correctly and that the format of the termcap description is correct. If it still does not work, check to see if there are some additional capabilities that need to be added to make it work. Also, certain terminals require special initialization commands. Check the technical guide to see which additional sequences you must add to the initialization string.

One way of preparing termcap descriptions is to examine the termcap entries for similar terminals. If you are trying to write a description for a terminal that is similar to one in the termcap file, you can use the tc command to indicate that all attributes for the new terminal are to be taken from the description of a terminal already in the termcap file. Then, you only need to specify the few differences.

Alternatively, you can manually copy the capabilities from a similar terminal and see if it works. Most terminals conform to a system of specifying escape sequences called the ANSI standard. Thus, if you have an ANSI standard terminal, you must be able to get about 90 percent of the capabilities by copying them from another ANSI terminal. The VT100 is an example of an ANSI terminal that has capabilities similar to many different terminals. For this reason, this document contains numerous references to the VT100 sequences in its examples.

Finally, if your terminal has a VT100 emulation mode, you can save time by jumping to VT100 emulation mode and using the VT100 termcap description. In most cases, it is necessary to make a termcap description. In other cases, the terminal works with a termcap description that is identical to the VT100 except that it contains the VT100 emulation sequence in its initialization string. If your terminal has VT100 emulation mode, we recommend that you try it, as a VT100 supports the most advanced features of the forms system.