xschem is a schematic capture program, it allows creation of hierarchical
representation of circuits with a top down approach. By focusing on
interfaces, hierarchy and instance properties, a complex system can be
described in terms of simpler building blocks. A VHDL or Verilog or Spice
netlist can be generated from the drawn schematic, allowing the simulation
of the circuit. Key feature of the program is its drawing engine written in C
and using directly the Xlib drawing primitives; this gives very good
speed performance, even on very big circuits. The user interface is
built with the Tcl-Tk toolkit, Tcl is also the extension language used.
