sentences:  VHDL was based on the Ada programming language, as well as on the experience gained with the earlier development of ISPS.Initially, Verilog and VHDL were used to document and simulate circuit designs already captured and described in another form (such as schematic files).HDL simulation enabled engineers to work at a higher level of abstraction than simulation at the schematic level, and thus increased design capacity from hundreds of transistors to thousands.