Underscores are better for readability other kinds of things like unit test names or filenames. Because humans tend to shortcut, it becomes camelCase for everything, including other inappropriate attributes out of laziness, which is aggravating. It's too bad that distinction has not been properly subjected to rigor yet.
It's a system for semantic variable naming.
What Did Terrence Eat?
What evidence? Where?
http://www.art.net/~hopkins/Don/unix-haters/x-windows/motif....
TLDR:
s_CALLBACK_CUR_INSERT Lexical_Bindings_For_XmTextVerifyCallbackStruct XtPointer call_data XLTYPE_CALLBACKOBJ /* How long can this go on???? */ Set_Call_Data_For_XmTextVerifyCallbackStruct Wcb_Meta_Callbackproc XmAnyCallbackStruct doit newInsert XmCR_MODIFYING_TEXT_VALUE cdr car ep /* do nothing for most cases... */ Cvt_XmRXmString_to_LVAL GetValues_Union Resource_Instance WINTERP_MOTIF_111 XmStrings XtGetValues XtPointer_value cv_xmstring XmBulletinBoard XmNdialogTitle XmNnoMatchString XmNlabelString XmNtitleString XmRowColumn XtGetValues XmStringFree /* This is so totally ridiculous: there's NO WAY to tell Motif that any button can select a menu item. Only one button can have that honor. */ /* If this function looks like it does a lot more work than it needs to, you're right. Blame the Motif scrollbar for not being smart about updating its appearance. */ xm_update_scrollbar widget_instance Widget widget scrollbar_values pane_maximum widget_sliderSize new_sliderSize h_water l_water XtVaGetValues XmNheight XmNpaneMaximum XmNsliderSize widget_sliderSize XmNrefigureMode maximum minimum INT_MAX percent XmScrollBarSetValues ARMANDACTIVATE_KLUDGE DND_KLUDGE *dialog*button1.accelerators:#override Ctrl<KeyPress>m: ArmAndActivate() /* sets the parent window to 0 to fool Motif into not generating a grab */ USE_MOTIF xlw_unmunge_class_resize XlwMenuResize