Placing values onto nets and variables are called assignments. There are three basic forms:
An assignment has two parts - right-hand side (RHS) and left-hand side (LHS) with an equal symbol (=) or a less than-equal symbol (<=) in between. The RHS can contain any expression that evaluates to a final value while the LHS indicates a net or a variable to which the value in RHS is being assigned.
Legal LHS values
Bit-select or part-select of a vector reg, integer or time variable