diff --git a/Project Backups/circuit1 [Autosaved].pdsprj b/Project Backups/circuit1 [Autosaved].pdsprj
new file mode 100644
index 0000000..3a58c6b
Binary files /dev/null and b/Project Backups/circuit1 [Autosaved].pdsprj differ
diff --git a/circuit1.pdsprj b/circuit1.pdsprj
new file mode 100644
index 0000000..59bb1eb
Binary files /dev/null and b/circuit1.pdsprj differ
diff --git a/homework5/.eide/eide.json b/homework5/.eide/eide.json
index c52fb13..8e7c5be 100644
--- a/homework5/.eide/eide.json
+++ b/homework5/.eide/eide.json
@@ -18,7 +18,9 @@
   },
   "targets": {
     "Debug": {
-      "excludeList": [],
+      "excludeList": [
+        "src/test.c"
+      ],
       "toolchain": "Keil_C51",
       "compileConfig": {
         "options": "null"
diff --git a/homework5/homework5.code-workspace b/homework5/homework5.code-workspace
index 8c192af..7177d54 100644
--- a/homework5/homework5.code-workspace
+++ b/homework5/homework5.code-workspace
@@ -1,44 +1,45 @@
 {
-    "folders": [
-        {
-            "path": "."
-        }
-    ],
-    "settings": {
-        "files.autoGuessEncoding": true,
-        "C_Cpp.default.configurationProvider": "cl.eide",
-        "C_Cpp.errorSquiggles": "disabled",
-        "files.associations": {
-            ".eideignore": "ignore",
-            "*.a51": "a51",
-            "*.h": "c",
-            "*.c": "c",
-            "*.hxx": "cpp",
-            "*.hpp": "cpp",
-            "*.c++": "cpp",
-            "*.cpp": "cpp",
-            "*.cxx": "cpp",
-            "*.cc": "cpp"
-        },
-        "[yaml]": {
-            "editor.insertSpaces": true,
-            "editor.tabSize": 4,
-            "editor.autoIndent": "advanced"
-        }
-    },
-    "extensions": {
-        "recommendations": [
-            "cl.eide",
-            "keroc.hex-fmt",
-            "xiaoyongdong.srecord",
-            "hars.cppsnippets",
-            "zixuanwang.linkerscript",
-            "redhat.vscode-yaml",
-            "IBM.output-colorizer",
-            "cschlosser.doxdocgen",
-            "ms-vscode.vscode-serial-monitor",
-            "alefragnani.project-manager",
-            "cl.stm8-debug"
-        ]
+  "folders": [
+    {
+      "path": "."
     }
-}
\ No newline at end of file
+  ],
+  "settings": {
+    "files.autoGuessEncoding": true,
+    "C_Cpp.default.configurationProvider": "cl.eide",
+    "C_Cpp.errorSquiggles": "disabled",
+    "files.associations": {
+      ".eideignore": "ignore",
+      "*.a51": "a51",
+      "*.h": "c",
+      "*.c": "c",
+      "*.hxx": "cpp",
+      "*.hpp": "cpp",
+      "*.c++": "cpp",
+      "*.cpp": "cpp",
+      "*.cxx": "cpp",
+      "*.cc": "cpp",
+      "REG52.H": "cpp"
+    },
+    "[yaml]": {
+      "editor.insertSpaces": true,
+      "editor.tabSize": 4,
+      "editor.autoIndent": "advanced"
+    }
+  },
+  "extensions": {
+    "recommendations": [
+      "cl.eide",
+      "keroc.hex-fmt",
+      "xiaoyongdong.srecord",
+      "hars.cppsnippets",
+      "zixuanwang.linkerscript",
+      "redhat.vscode-yaml",
+      "IBM.output-colorizer",
+      "cschlosser.doxdocgen",
+      "ms-vscode.vscode-serial-monitor",
+      "alefragnani.project-manager",
+      "cl.stm8-debug"
+    ]
+  }
+}
diff --git a/homework5/src/homework5.h b/homework5/src/homework5.h
index 3d9cd41..0051786 100644
--- a/homework5/src/homework5.h
+++ b/homework5/src/homework5.h
@@ -1,10 +1,15 @@
 // homework5.h
 /*
  * this header defines:
+ * variables:
  * 1. pin numbers to control the LED and the Seg.
- * 2. the function to control the LED and the Seg.
- * 3. the function to display the number on the Seg.
- * 4. the function to set the 38 transistors.
+ * 2. sdf for timer
+ * functions:
+ * 1. control the LED and the Seg.
+ * 2. to display the number on the Seg.
+ * 3. to set the 38 transistors.
+ * 4. to display the number on the Seg.
+ * 5. timer.
  */
 
 #include <REG52.H>
@@ -37,4 +42,26 @@ void set38Transistors(unsigned char number) // set the 38 transistors.
     ADDR2 = (number & 0x04) >> 2;
     ADDR1 = (number & 0x02) >> 1;
     ADDR0 = (number & 0x01);
+}
+// timer
+int timer(unsigned int ms)
+{
+    TMOD &= 0xF0; // set the timer mode to 16-bit timer mode.
+    TMOD |= 0x01; // set the timer mode to 16-bit timer mode.
+
+    // 1ms timer definition:
+    TH0 = 0XFC;
+    TL0 = 0X18;
+
+    // start the timer:
+    TR0 = 1;
+
+    while (ms--) {
+        while (!TF0) {} // wait for the timer to overflow.
+        TF0 = 0;        // clear the timer flag.
+        TH0 = 0XFC;     // reload the timer value.
+        TL0 = 0X18;     // reload the timer value.
+    }
+    TR0 = 0; // stop the timer.
+    return 0;
 }
\ No newline at end of file
diff --git a/homework5/src/test1.c b/homework5/src/test1.c
new file mode 100644
index 0000000..c5c0a07
--- /dev/null
+++ b/homework5/src/test1.c
@@ -0,0 +1,63 @@
+// test1.c
+// 数码管动态显示自己学号后6位
+// display the last 6 digits of your student ID on the Seg.
+
+#include "homework5.h"
+
+unsigned char code LedChar[] = {
+    0xC0,
+    0xF9,
+    0XA4,
+    0XB0,
+    0X99,
+    0X92,
+    0X82,
+    0XF8,
+    0X80,
+    0X90,
+    0X88,
+    0X83,
+    0XC6,
+    0XA1,
+    0X86,
+    0X8E,
+};
+unsigned char LedBuff[6] = {
+    0xFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF};
+unsigned char i = 0;
+
+void test1()
+{
+    // display the number on the Seg.
+    LedBuff[5] = LedChar[1];
+    LedBuff[4] = LedChar[3];
+    LedBuff[3] = LedChar[0];
+    LedBuff[2] = LedChar[0];
+    LedBuff[1] = LedChar[7];
+    LedBuff[0] = LedChar[1];
+    while (1) {
+        /*
+         * seg id on 38 transistors:
+         * Y0: LEDS0 the latest digit.
+         * Y1: LEDS1 the second digit.
+         * Y2: LEDS2 the third digit.
+         * Y3: LEDS3 the forth digit.
+         * Y4: LEDS4 the fifth digit.
+         * Y5: LEDS5 the highest digit.
+         * Y6: 2LED to the LED lights.
+         */
+        set38Transistors(i);
+        P2 = LedBuff[i];
+        i++;
+        timer(1);
+        // reset the i to 0 when it reaches 6.
+        if (i >= 6) {
+            i = 0;
+        }
+    }
+}
+
+void main()
+{
+    test1();
+}
\ No newline at end of file