In the latest versions of dataComet, installation of the "dataComet keyboard" keyboard layout is still desirable if 1) you're using English and 2) you use the Option key to trigger key macros using certain Option-key combinations. You install the keyboard layout by drag-and-dropping it onto the "System" File in the Macintosh "System Folder". If you're using another language and connecting to a host using an 8-bit character set, you do not need to install the "dataComet keyboard" in your System.
If you install the "dataComet keyboard" layout and turn on the "Control Global..." item "Remap Option-key combinations", all Option-key combinations will be handled immediately with no confusion. Otherwise, the standard Macintosh keyboard layout treats the Option key as a special key when it is used with certain characters (Option-e, i, n, u, and `). When these key-combinations are pressed, the standard keyboard layout interprets the first character as a "diacritical mark," i.e. a special mark that accents certain foreign characters, and interprets the next key pressed as the character you want to place the diacritical mark over, producing just one character.
For example, dataComet (prior to 4.41) used to map some Option-keys into IBM PF keys (and still does for old Mac+ keyboards that have no "Control" key). If you're using one of those keyboards with the standard keyboard layout and try to send PF5 in IBM 3270 mode by pressing Option-i, nothing happens on the first keystroke. If you press Option-i again, the keyboard layout will report to dataComet that Option-i has been pressed, and dataComet will send a PF5; the bad news is that the *next* keystroke may be remapped too! dataComet has no way of knowing what's going on, since the System is handling the remapping. After much research, it seems that the only reliable way to defeat this remapping is to install a different keyboard layout. (NCSA Telnet, e.g., also requires the installation of a keyboard layout).
The "dataComet keyboard" keyboard layout, when installed in the System, treats all Option-key combinations as normal keys which are handed over to dataComet immediately without further interpretation by the System, avoiding confusion and possible errors which can result from handling some keys in a "special" way. This resource can't be installed in the System automatically... sometimes the System file becomes "unstable" due to errors in the formatting of its resource fork, and the addition of the keyboard layout (or other resources) to the System folder can cause the System to go "over the edge" and crash when the Macintosh is restarted. Because of this risk, and the crucial importance of maintaining a clean System file, dataComet does not install this resource itself.
With dataComet, you have two options:
1) Skip installing the "dataComet keyboard" resource.
A dialog will appear when Comet is launched which states:
"Please install the 'dataComet keyboard' keyboard layout in your
System file by dragging it over the System icon and releasing the mouse
button. To avoid this alert, turn off 'Remap Option key-combinations' in
the Control Global dialog."
If you follow these instructions, you will avoid the alert, and can enjoy
the behavior of the standard keyboard layout!
2) Install the "dataComet keyboard" resource. All Option-key combinations will behave as a "naive" user would expect, including producing
