diff --git a/_03.串/_a.串.c b/_03.串/_a.串.c
index fd284e3..eef26af 100644
--- a/_03.串/_a.串.c
+++ b/_03.串/_a.串.c
@@ -13,6 +13,7 @@ typedef int Status;
 typedef int ElemType;
 
 typedef char String[MAXSIZE + 1];
+// 0λÖÃÓÃÀ´´æ×Ö·û´®³¤¶È
 
 Status StrAssign(String T, char *chars)
 {
@@ -33,16 +34,99 @@ Status StrAssign(String T, char *chars)
     }
 }
 
-int main(){
-    //char chars[]="ABCD";
-    String T = "1233";
-    //StrAssign(T,chars);
-    printf("%s \n",T);
-    printf("%c",T[3]);
+Status StrCopy(String T, String S)
+{
+    // ×¢Òâ´Ë´¦²¢Ã»ÓÐά»¤T[0]£¬´æÒÉ
+    int i;
+    for (i = 0; i <= S[0]; i++)
+    {
+        T[i] = S[i];
+    }
+    return OK;
+}
+
+Status StrEmpty(String S)
+{
+    if (S[0] == 0)
+    {
+        return TRUE;
+    }
+    else
+    {
+        return FALSE;
+    }
+}
+
+int StrCompare(String S, String T)
+{
+    // ÈôS>T,·µ»ØÖµ>0;S=T,·µ»ØÖµ=0£»·ñÔò<0
+    int i;
+    for (i = 1; i <= S[0] && i <= T[0]; i++)
+    {
+        if (S[i] != T[i])
+        {
+            return S[i] - T[i];
+        }
+    }
+    return S[0] - T[0];
+}
+
+int StrLength(String S)
+{
+    return S[0];
+}
+
+Status ClearString(String S)
+{
+    // ¿ÉÒÔ×¢Òâµ½StringΪÒýÓÃÐÍ
+    S[0] = 0;
+    return OK;
+}
+
+Status Concat(String T, String S1, String S2)
+{
+    // ÓÃT·µ»ØS1+S2Æ´½Ó´®¡£Èôδ½Ø¶Ï·µ»ØTRUE£¬·ñÔòFALSE
+    int i;
+    if (S1[0] + S2[0] <= MAXSIZE)
+    {
+        // δ½Ø¶Ï
+        for (i = 1; i <= S1[0]; i++)
+        {
+            T[i] = S1[i];
+        }
+        for (i = 1; i <= MAXSIZE - S1[0]; i++)
+        // iÉϽç´æÒÉ
+        {
+            T[S1[0] + i] = S2[i];
+        }
+        T[0] = S1[0] + S2[0];
+        return TRUE;
+    }
+    else
+    {
+        //½Ø¶ÏS2
+        for (i = 1; i < S1[0]; i++)
+        {
+            T[i] = S1[i];
+        }
+        for (i = 1; i <= MAXSIZE - S1[0]; i++)
+        {
+            T[S1[0] + i] = S2[i];
+        }
+        T[0] = MAXSIZE;
+        return FALSE;
+    }
+}
 
 
 
-    
+int main()
+{
+    char chars[] = "ABCD";
+    String T = " ";
+    StrAssign(T, chars);
+    printf("%s \n", T);
+    printf("%c", T[3]);
 
     getchar();
     return OK;
diff --git a/a.out b/a.out
index 2931e16..84d5a09 100644
Binary files a/a.out and b/a.out differ