components

circuits
   EDA
   hierarchical, parametric drawing
   component libraries, design rules
   schematic entry, component placement, routing, simulation, fabrication
   drafting tape
   drawing
   Eagle fab.lbr
   Kicad gEDA
   OrCAD Altium
   Cadence Synopsys Mentor Tanner Magic
   Spice ngspice TCLspice
   Verilog VHDL
   fab modules
      pcb.cad
      image import

assignment
   redraw the echo hello-world board,
      add (at least) a button and LED (with current-limiting resistor),
      check the design rules,
      and make it