diff --git a/_03.串/01串_String.c b/_03.串/01串_String.c
new file mode 100644
index 0000000..db9b232
--- /dev/null
+++ b/_03.串/01串_String.c
@@ -0,0 +1,318 @@
+#include "string.h"
+#include "stdio.h"    
+#include "stdlib.h"   
+#include "io.h"  
+#include "math.h"  
+#include "time.h"
+
+#define OK 1
+#define ERROR 0
+#define TRUE 1
+#define FALSE 0
+
+#define MAXSIZE 40 /* ´æ´¢¿Õ¼ä³õʼ·ÖÅäÁ¿ */
+
+typedef int Status;		/* StatusÊǺ¯ÊýµÄÀàÐÍ,ÆäÖµÊǺ¯Êý½á¹û״̬´úÂ룬ÈçOKµÈ */
+typedef int ElemType;	/* ElemTypeÀàÐ͸ù¾Ýʵ¼ÊÇé¿ö¶ø¶¨£¬ÕâÀï¼ÙÉèΪint */
+
+typedef char String[MAXSIZE+1]; /*  0ºÅµ¥Ôª´æ·Å´®µÄ³¤¶È */
+
+/* Éú³ÉÒ»¸öÆäÖµµÈÓÚcharsµÄ´®T */
+Status StrAssign(String T,char *chars)
+{ 
+	int i;
+	if(strlen(chars)>MAXSIZE)
+		return ERROR;
+	else
+	{
+		T[0]=strlen(chars);
+		for(i=1;i<=T[0];i++)
+			T[i]=*(chars+i-1);
+		return OK;
+	}
+}
+
+/* ÓÉ´®S¸´ÖƵô®T */
+Status StrCopy(String T,String S)
+{ 
+	int i;
+	for(i=0;i<=S[0];i++)
+		T[i]=S[i];
+	return OK;
+}
+
+/* ÈôSΪ¿Õ´®,Ôò·µ»ØTRUE,·ñÔò·µ»ØFALSE */
+Status StrEmpty(String S)
+{ 
+	if(S[0]==0)
+		return TRUE;
+	else
+		return FALSE;
+}
+
+/*  ³õʼÌõ¼þ: ´®SºÍT´æÔÚ */
+/*  ²Ù×÷½á¹û: ÈôS>T,Ôò·µ»ØÖµ>0;ÈôS=T,Ôò·µ»ØÖµ=0;ÈôS<T,Ôò·µ»ØÖµ<0 */
+int StrCompare(String S,String T)
+{ 
+	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];
+}
+
+/* ·µ»Ø´®µÄÔªËظöÊý */
+int StrLength(String S)
+{ 
+	return S[0];
+}
+
+/* ³õʼÌõ¼þ:´®S´æÔÚ¡£²Ù×÷½á¹û:½«SÇåΪ¿Õ´® */
+Status ClearString(String S)
+{ 
+	S[0]=0;/*  Áî´®³¤ÎªÁã */
+	return OK;
+}
+
+/* ÓÃT·µ»ØS1ºÍS2Áª½Ó¶ø³ÉµÄд®¡£Èôδ½Ø¶Ï£¬Ôò·µ»ØTRUE£¬·ñÔòFALSE */
+Status Concat(String T,String S1,String S2)
+{
+	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<=S2[0];i++)
+			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;
+	}
+}
+
+/* ÓÃSub·µ»Ø´®SµÄµÚpos¸ö×Ö·ûÆ𳤶ÈΪlenµÄ×Ó´®¡£ */
+Status SubString(String Sub,String S,int pos,int len)
+{
+	int i;
+	if(pos<1||pos>S[0]||len<0||len>S[0]-pos+1)
+		return ERROR;
+	for(i=1;i<=len;i++)
+		Sub[i]=S[pos+i-1];
+	Sub[0]=len;
+	return OK;
+}
+
+/* ·µ»Ø×Ó´®TÔÚÖ÷´®SÖеÚpos¸ö×Ö·ûÖ®ºóµÄλÖá£Èô²»´æÔÚ,Ôòº¯Êý·µ»ØֵΪ0¡£ */
+/* ÆäÖÐ,T·Ç¿Õ,1¡Üpos¡ÜStrLength(S)¡£ */
+int Index(String S, String T, int pos) 
+{
+	int i = pos;	/* iÓÃÓÚÖ÷´®SÖе±Ç°Î»ÖÃϱêÖµ£¬Èôpos²»Îª1£¬Ôò´ÓposλÖÿªÊ¼Æ¥Åä */
+	int j = 1;				/* jÓÃÓÚ×Ó´®TÖе±Ç°Î»ÖÃϱêÖµ */
+	while (i <= S[0] && j <= T[0]) /* ÈôiСÓÚSµÄ³¤¶È²¢ÇÒjСÓÚTµÄ³¤¶Èʱ£¬Ñ­»·¼ÌÐø */
+	{
+		if (S[i] == T[j]) 	/* Á½×ÖĸÏàµÈÔò¼ÌÐø */
+      	{
+			++i;
+         	++j; 
+      	} 
+      	else 				/* Ö¸ÕëºóÍËÖØпªÊ¼Æ¥Åä */
+      	{  
+         	i = i-j+2;		/* iÍ˻ص½ÉÏ´ÎÆ¥ÅäÊ×λµÄÏÂһλ */
+         	j = 1; 			/* jÍ˻ص½×Ó´®TµÄÊ×λ */
+      	}      
+	}
+	if (j > T[0]) 
+		return i-T[0];
+	else 
+		return 0;
+}
+
+
+/*  TΪ·Ç¿Õ´®¡£ÈôÖ÷´®SÖеÚpos¸ö×Ö·ûÖ®ºó´æÔÚÓëTÏàµÈµÄ×Ó´®£¬ */
+/*  Ôò·µ»ØµÚÒ»¸öÕâÑùµÄ×Ó´®ÔÚSÖеÄλÖ㬷ñÔò·µ»Ø0 */
+int Index2(String S, String T, int pos) 
+{
+	int n,m,i;
+	String sub;
+	if (pos > 0) 
+	{
+		n = StrLength(S);	/* µÃµ½Ö÷´®SµÄ³¤¶È */
+		m = StrLength(T);	/* µÃµ½×Ó´®TµÄ³¤¶È */
+		i = pos;
+		while (i <= n-m+1) 
+		{
+			SubString (sub, S, i, m);	/* È¡Ö÷´®ÖеÚi¸öλÖó¤¶ÈÓëTÏàµÈµÄ×Ó´®¸øsub */
+			if (StrCompare(sub,T) != 0)    /* Èç¹ûÁ½´®²»ÏàµÈ */
+				++i;
+			else 				/* Èç¹ûÁ½´®ÏàµÈ */
+				return i;		/* Ôò·µ»ØiÖµ */
+		}
+	}
+	return 0;	/* ÈôÎÞ×Ó´®ÓëTÏàµÈ£¬·µ»Ø0 */
+}
+
+
+/*  ³õʼÌõ¼þ: ´®SºÍT´æÔÚ,1¡Üpos¡ÜStrLength(S)+1 */
+/*  ²Ù×÷½á¹û: ÔÚ´®SµÄµÚpos¸ö×Ö·û֮ǰ²åÈë´®T¡£ÍêÈ«²åÈë·µ»ØTRUE,²¿·Ö²åÈë·µ»ØFALSE */
+Status StrInsert(String S,int pos,String T)
+{ 
+	int i;
+	if(pos<1||pos>S[0]+1)
+		return ERROR;
+	if(S[0]+T[0]<=MAXSIZE)
+	{ /*  ÍêÈ«²åÈë */
+		for(i=S[0];i>=pos;i--)
+			S[i+T[0]]=S[i];
+		for(i=pos;i<pos+T[0];i++)
+			S[i]=T[i-pos+1];
+		S[0]=S[0]+T[0];
+		return TRUE;
+	}
+	else
+	{ /*  ²¿·Ö²åÈë */
+		for(i=MAXSIZE;i<=pos;i--)
+			S[i]=S[i-T[0]];
+		for(i=pos;i<pos+T[0];i++)
+			S[i]=T[i-pos+1];
+		S[0]=MAXSIZE;
+		return FALSE;
+	}
+}
+
+/*  ³õʼÌõ¼þ: ´®S´æÔÚ,1¡Üpos¡ÜStrLength(S)-len+1 */
+/*  ²Ù×÷½á¹û: ´Ó´®SÖÐɾ³ýµÚpos¸ö×Ö·ûÆ𳤶ÈΪlenµÄ×Ó´® */
+Status StrDelete(String S,int pos,int len)
+{ 
+	int i;
+	if(pos<1||pos>S[0]-len+1||len<0)
+		return ERROR;
+	for(i=pos+len;i<=S[0];i++)
+		S[i-len]=S[i];
+	S[0]-=len;
+	return OK;
+}
+
+/*  ³õʼÌõ¼þ: ´®S,TºÍV´æÔÚ,TÊÇ·Ç¿Õ´®£¨´Ëº¯ÊýÓë´®µÄ´æ´¢½á¹¹Î޹أ© */
+/*  ²Ù×÷½á¹û: ÓÃVÌæ»»Ö÷´®SÖгöÏÖµÄËùÓÐÓëTÏàµÈµÄ²»ÖصþµÄ×Ó´® */
+Status Replace(String S,String T,String V)
+{ 
+	int i=1; /*  ´Ó´®SµÄµÚÒ»¸ö×Ö·ûÆð²éÕÒ´®T */
+	if(StrEmpty(T)) /*  TÊÇ¿Õ´® */
+		return ERROR;
+	do
+	{
+		i=Index(S,T,i); /*  ½á¹ûiΪ´ÓÉÏÒ»¸öiÖ®ºóÕÒµ½µÄ×Ó´®TµÄλÖà */
+		if(i) /*  ´®SÖдæÔÚ´®T */
+		{
+			StrDelete(S,i,StrLength(T)); /*  ɾ³ý¸Ã´®T */
+			StrInsert(S,i,V); /*  ÔÚÔ­´®TµÄλÖòåÈë´®V */
+			i+=StrLength(V); /*  ÔÚ²åÈëµÄ´®VºóÃæ¼ÌÐø²éÕÒ´®T */
+		}
+	}while(i);
+	return OK;
+}
+
+/*  Êä³ö×Ö·û´®T */
+void StrPrint(String T)
+{ 
+	int i;
+	for(i=1;i<=T[0];i++)
+		printf("%c",T[i]);
+	printf("\n");
+}
+
+
+int main()
+{
+	
+	int i,j;
+	Status k;
+	char s;
+	String t,s1,s2;
+	printf("ÇëÊäÈë´®s1: ");
+	
+	k=StrAssign(s1,"abcd");
+	if(!k)
+	{
+		printf("´®³¤³¬¹ýMAXSIZE(=%d)\n",MAXSIZE);
+		exit(0);
+	}
+	printf("´®³¤Îª%d ´®¿Õ·ñ£¿%d(1:ÊÇ 0:·ñ)\n",StrLength(s1),StrEmpty(s1));
+	StrCopy(s2,s1);
+	printf("¿½±´s1Éú³ÉµÄ´®Îª: ");
+	StrPrint(s2);
+	printf("ÇëÊäÈë´®s2: ");
+	
+	k=StrAssign(s2,"efghijk");
+	if(!k)
+	{
+		printf("´®³¤³¬¹ýMAXSIZE(%d)\n",MAXSIZE);
+		exit(0);
+	}
+	i=StrCompare(s1,s2);
+	if(i<0)
+		s='<';
+	else if(i==0)
+		s='=';
+	else
+		s='>';
+	printf("´®s1%c´®s2\n",s);
+	k=Concat(t,s1,s2);
+	printf("´®s1Áª½Ó´®s2µÃµ½µÄ´®tΪ: ");
+	StrPrint(t);
+	if(k==FALSE)
+		printf("´®tÓнضÏ\n");
+	ClearString(s1);
+	printf("ÇåΪ¿Õ´®ºó,´®s1Ϊ: ");
+	StrPrint(s1);
+	printf("´®³¤Îª%d ´®¿Õ·ñ£¿%d(1:ÊÇ 0:·ñ)\n",StrLength(s1),StrEmpty(s1));
+	printf("Çó´®tµÄ×Ó´®,ÇëÊäÈë×Ó´®µÄÆðʼλÖÃ,×Ó´®³¤¶È: ");
+
+	i=2;
+	j=3;
+	printf("%d,%d \n",i,j);
+
+	k=SubString(s2,t,i,j);
+	if(k)
+	{
+		printf("×Ó´®s2Ϊ: ");
+		StrPrint(s2);
+	}
+	printf("´Ó´®tµÄµÚpos¸ö×Ö·ûÆð,ɾ³ýlen¸ö×Ö·û£¬ÇëÊäÈëpos,len: ");
+	
+	i=4;
+	j=2;
+	printf("%d,%d \n",i,j);
+
+
+	StrDelete(t,i,j);
+	printf("ɾ³ýºóµÄ´®tΪ: ");
+	StrPrint(t);
+	i=StrLength(s2)/2;
+	StrInsert(s2,i,t);
+	printf("ÔÚ´®s2µÄµÚ%d¸ö×Ö·û֮ǰ²åÈë´®tºó,´®s2Ϊ:\n",i);
+	StrPrint(s2);
+	i=Index(s2,t,1);
+	printf("s2µÄµÚ%d¸ö×ÖĸÆðºÍtµÚÒ»´ÎÆ¥Åä\n",i);
+	SubString(t,s2,1,1);
+	printf("´®tΪ£º");
+	StrPrint(t);
+	Concat(s1,t,t);
+	printf("´®s1Ϊ£º");
+	StrPrint(s1);
+	Replace(s2,t,s1);
+	printf("Óô®s1È¡´ú´®s2Öкʹ®tÏàͬµÄ²»ÖصþµÄ´®ºó,´®s2Ϊ: ");
+	StrPrint(s2);
+
+
+	return 0;
+}
+
diff --git a/_03.串/_a.串.c b/_03.串/_a.串.c
new file mode 100644
index 0000000..fd284e3
--- /dev/null
+++ b/_03.串/_a.串.c
@@ -0,0 +1,49 @@
+#include "string.h"
+#include "stdio.h"
+#include "stdlib.h"
+#include "io.h"
+
+#define MAXSIZE 40
+#define OK 1
+#define ERROR 0
+#define TRUE 1
+#define FALSE 0
+
+typedef int Status;
+typedef int ElemType;
+
+typedef char String[MAXSIZE + 1];
+
+Status StrAssign(String T, char *chars)
+{
+    // Éú³ÉÒ»¸öÆäÖµµÈÓÚcharsµÄ´®T
+    int i;
+    if (strlen(chars) > MAXSIZE)
+    {
+        return ERROR;
+    }
+    else
+    {
+        T[0] = strlen(chars);
+        for (i = 1; i <= T[0]; i++)
+        {
+            T[i] = *(chars + i - 1);
+        }
+        return OK;
+    }
+}
+
+int main(){
+    //char chars[]="ABCD";
+    String T = "1233";
+    //StrAssign(T,chars);
+    printf("%s \n",T);
+    printf("%c",T[3]);
+
+
+
+    
+
+    getchar();
+    return OK;
+}
\ No newline at end of file
diff --git a/a.out b/a.out
index 9589c50..2931e16 100644
Binary files a/a.out and b/a.out differ