标量(scalar)是没有范围声明的1-bit的线网(net)或reg。
向量(vector)是带有范围声明的multi-bit的线网(net)或reg。

  例子:
  wand w;                              // a scalar net of type "wand"
  wire w1, w2;                          // declares two wires
  tri [15:0] busa;                      // a three-state 16-bit bus
  reg a;                                // a scalar reg
  reg [3:0] v;                          // a 4-bit vector reg made up of v[3],
                                        // v[2], v[1], and v[0]
  reg signed [3:0] signed_reg;          // a 4-bit vector in range -8 to 7
  reg [4:-1] b;                         // a 6-bit vector reg
  reg [4:0] x, y, z;                    // declares three 5-bit regs