The always @() syntax was added to the IEEE Verilog Std in 2001. All modern Verilog tools (simulators, synthesis, etc.) support this syntax. Here is a quote from the LRM (1800-2009): An incomplete event_expression list of an event control is a common source of bugs in register transfer level (RTL) simulations. The implicit event_expression, @, is a convenient shorthand that eliminates these ...
The (*) means "build the sensitivity list for me". For example, if you had a statement a = b + c; then you'd want a to change every time either b or c changes. In other words, a is "sensitive" to b & c. So to set this up: always @( b or c ) begin a = b + c; end But imagine you had a large always block that was sensitive to loads of signals. Writing the sensitivity list would take ages. In fact ...
verilog - What does always block @ (*) means? - Stack Overflow
So, always use "always @*" or better yet "always_comb" and forget about the concept of sensitivity lists. If the item in the code is evaluated it will trigger the process. Simple as that. It an item is in an if/else, a case, assigned to a variable, or anything else, it will be "evaluated" and thus cause the process to be triggered.
I am totally confused among these 4 terms: always_ff, always_comb, always_latch and always. How and for what purpose can these be used?
The difference between forever and always is that always can exist as a "module item", which is the name that the Verilog spec gives to constructs that may be written directly within a module, not contained within some other construct. initial is also a module item. always blocks are repeated, whereas initial blocks are run once at the start of ...