HDL And Programming Language
An HDL is analogous to a software programming language, but with major differences. Programming languages are inherently procedural (single-threaded), with limited syntactical and semantic support to handle concurrency. HDLs, on the other hand, can model multiple parallel processes (such as flipflops, adders, etc.) that automatically execute independently of one another. Any change to the process's input automatically triggers an update in the simulator's process stack. Both programming languages and HDLs are processed by a compiler (usually called a synthesizer in the HDL case), but with different goals. For HDLs, 'compiler' refers to synthesis, a process of transforming the HDL code-listing into a physically-realizable gate netlist. The netlist-output can take any of many forms: a "simulation" netlist with gate-delay information, a "handoff" netlist for post-synthesis place&route, or a generic industry-standard EDIF format (for subsequent conversion to a JEDEC-format file.)