Drawing and Modifying Objects
Precision input
AutoCAD accepts absolute coordinates (x,y), relative Cartesian (@x,y), and relative polar (@distance<angle) entry. With Dynamic Input and direct distance entry, move the cursor in the desired direction and type the distance. ORTHO constrains to horizontal and vertical; POLAR tracking adds angled increments; OSNAP snaps to endpoints, midpoints, centers, intersections, and other geometric points. Object Snap Tracking (OTRACK) aligns points from snap markers.
Creating geometry
Core commands include LINE, PLINE, CIRCLE, ARC, RECTANG, POLYGON, ELLIPSE, SPLINE, and POINT. Polylines are single objects with optional width; lines are separate segments. Construction aids include XLINE and RAY.
Modifying geometry
MOVE, COPY, ROTATE, SCALE, MIRROR, and ARRAY transform objects. STRETCH moves only the vertices inside a crossing window and leaves the rest anchored. TRIM and EXTEND cut or lengthen to edges, or to all objects in the default quick mode. OFFSET creates parallel lines or concentric circles; FILLET and CHAMFER round or bevel corners, with radius 0 producing a sharp corner. JOIN combines collinear lines or open polylines; EXPLODE breaks compound objects apart. Grips allow direct editing, and Ctrl cycles through grip options.
Traps in questions: MIRROR keeps the source unless you answer No to erasing it; COPY duplicates within the drawing while COPYCLIP goes to the clipboard; a crossing window selects objects that touch it while a window selects only fully enclosed objects; STRETCH does nothing to circles or text placed wholly inside the window; EXPLODE on a polyline loses its width.
Worked example: to lengthen a line exactly 25 mm to the right, start STRETCH, use a crossing window around the right endpoint only, turn ORTHO on, and type 25. Rule: type @ for relative coordinates or the distance directly for direct distance entry.