diff --git a/digital_tube/dt.v b/digital_tube/dt.v
index c6f6d97..1769424 100644
--- a/digital_tube/dt.v
+++ b/digital_tube/dt.v
@@ -7,11 +7,6 @@ module dt(
     output reg S1, S2, S3, S4
 );
 
-parameter _SELECT_1 = 4'b1110;
-parameter _SELECT_2 = 4'b1101;
-parameter _SELECT_3 = 4'b1011;
-parameter _SELECT_4 = 4'b0111;
-
 
 //                     ABCDEFG
 parameter _SHOW_0 = 8'B1111110;
@@ -55,13 +50,12 @@ always @(data) begin
         default: ;
     endcase
 
-    case (data[7:5])
-        3'b000: {S4, S3, S2, S1} = _SELECT_1;
-        3'b001: {S4, S3, S2, S1} = _SELECT_2;
-        3'b010: {S4, S3, S2, S1} = _SELECT_3;
-        3'b011: {S4, S3, S2, S1} = _SELECT_4;
-        default: {S4, S3, S2, S1} = 4'b1111;
-    endcase 
+    if (data[7]) begin
+        {S4, S3, S2, S1} = ~(4'b0001 << data[6:5]);
+    end
+    else begin
+        {S4, S3, S2, S1} = 4'b1111;
+    end
 
 end
 endmodule
\ No newline at end of file
diff --git a/led/led_1.v b/led/led_1.v
index 95d0edc..c9c2953 100644
--- a/led/led_1.v
+++ b/led/led_1.v
@@ -67,7 +67,7 @@ wire [4:0]U;
 assign U = W & V; // 连个操作数 按位相与 赋值给U, 如果某个操作数宽度不够, 则对宽度小的操作数在左侧补0
 
 
-// 逻辑运算符 && || ! 只有1或者0 两个结果, 而 | & ^ ~ 则可以对多位进行操作得到多位的结果
+// 逻辑运算符 && || ! 只有1或者0 两个结果(比特位中只要有一个1, 那么该值就是1, 比如 3'b010 && 3'b100  两边都是1), 而 | & ^ ~ 则可以对多位进行操作得到多位的结果
 
 
 // 比较运算符