Autodesk AUTOCAD 2006, Command Reference Manual, Page: 874 / 1490

Straighten
Saves the location of the marked vertex while you move the X marker to any
other vertex.
Enter an option [Next/Previous/Go/eXit] <current>: Enter an option or press ENTER
Next
Moves the X marker to the next vertex.
Previous
Moves the X marker to the previous vertex.
Go
Deletes any segments and vertices between the two vertices you select,
replaces them with single straight line segments, and returns to Edit Vertex
mode. If you specify only one vertex by entering
go without moving the
X marker, the segment following that vertex is made straight if it is an arc.
Exit
Exits Straighten and returns to Edit Vertex mode.
To remove an arc segment that connects two straight segments of a polyline
and then to extend the straight segments until they intersect, use the FILLET
command with a fillet radius of 0.
Exit
Exits Edit Vertex mode.
Spline Curve
Fits a 3D B-spline curve to its control points. The SPLFRAME system variable
controls the accuracy and display of the control points for the 3D B-spline,
whose curves can be approximated only by line segments. Negative values for
spline segments are ignored.
850 | Chapter 17