System tasks and functions

Verilog includes a number of useful tasks and functions. These can be enabled and called in the same way as user defined tasks and functions. The system tasks and functions begin with the dollar sign to distinguish them from ordinary tasks and functions.

The most important system tasks and functions are described in the following categories:

• Display tasks
• File I/O tasks
• Timescale tasks
• Simulation control tasks
• Timing check tasks
• Simulation time functions
• Real conversion functions
• Random functions