在systemverilog中支援class，class與module有些相似，此class與c++中的class類似。

class只有經過了new()函式才真正開闢了記憶體，否則只是一個空的、沒有實際存在。

Sonet_static sta1；//此時只是一個空的sta1

sta1 = new();//真正開闢了記憶體空間，並進行了初始化，若在class中未實現new()函式，則會有系統預設new()，進行開闢記憶體工作。

static and automatic: static 變數為靜態的，在整個程式執行過程中都存在，並且無論被例項多少次，在記憶體中只存在一份，每次例項都是指向這一個地址，共享一個變數；automatic是每次例項均產生一個新的記憶體，互相不共享，是單獨、不同的，default預設是automatic。

static:

`timescale 1 ns / 1 ps 

program sim_top();
class data_packet;
static integer Data = 32'hff;// Static variable declaration
function new();
Data--;
endfunction
endclass

initial
begin
automatic data_packet packet_one = new;
automatic data_packet packet_two = new;
$display("%d--Value of static data packet before decrement", packet_one.Data);
$display("\n%d--Value of static data packet after decrement", packet_two.Data);
end
endprogram
 

#         253--Value of static data packet before decrement
# 
#         253--Value of static data packet after decrement

`timescale 1 ns / 1 ps 

program sim_top();
class data_packet;
//static integer Data = 32'hff;// Static variable declaration
integer Data = 32'hff;// Static variable declaration
function new();
Data--;
endfunction
endclass

initial
begin
automatic data_packet packet_one = new();
automatic data_packet packet_two = new();
$display("%d--Value of static data packet before decrement", packet_one.Data);
$display("\n%d--Value of static data packet after decrement", packet_two.Data);
end
endprogram
 

#         254--Value of static data packet before decrement
# 
#         254--Value of static data packet after decrement

`timescale 1 ns / 1 ps 

module sim_top();
 class Sonet_static;
static bit count = 1'b1;
bit indicator ;
function new();
indicator = count++;
endfunction
endclass

Sonet_static sta1,sta2;//objects of class
initial
begin
sta1 = new();
sta2 = new();
$display("First indicator = %d, count = %d", sta1.indicator, sta1.count);
$display("Second indicator = %d, count = %d", sta2.indicator, sta2.count);
end
endmodule

# First indicator = 1, count = 1
# Second indicator = 0, count = 1

automatic data_packet packet_one = new();