1. A computer accessible memory medium comprising program instructions, wherein the program instructions are executable to implement: displaying a circuit diagram on a display, wherein the circuit diagram comprises a plurality of electronic components connected by nets, wherein the circuit diagram comprises one or more modular blocks which represent a circuit portion in a hierarchical fashion; storing a global netlist that stores information regarding the nets of the circuit diagram; receiving user input modifying the circuit diagram; updating the global netlist in response to the user input modifying the circuit diagram; updating the circuit diagram on the display after said updating the global netlist, wherein said updating is performed based on the information in the updated global netlist; wherein said receiving user input, said updating the global netlist, and said updating the circuit diagram are performed a plurality of times, such that said updating the global netlist and said updating the circuit diagram are performed dynamically during edit time.