diff --git a/final/makefile b/final/makefile
index 6d99afc..0fdd791 100755
--- a/final/makefile
+++ b/final/makefile
@@ -3,7 +3,7 @@ all: cos2000.img
 cos2000.img:
 	(dd if=/dev/zero of=cos2000.img count=2880 bs=512)
 	(mkfs.msdos -F 12 -n "COS2000" cos2000.img)
-	(mkdir ./mnt)
+	(mkdir ./mnt -p)
 	(fusefat cos2000.img ./mnt -o rw+)
 	(cp ../boot/loader.sys ./mnt/)
 	(cp ../system/system.sys ./mnt/;sync)
diff --git a/include/string.h b/include/string.h
index 2db80d1..c9dacf9 100755
--- a/include/string.h
+++ b/include/string.h
@@ -5,4 +5,10 @@ u32 strlen(const u8 *src);
 u8 *strchr(const u8 *src, u8 achar);
 u8 *strncpy(const u8 *src,u8 *des,u32 count);
 u8 *strcat(const u8 *src,u8 *des);
-u8* strcpy(const u8 *src, u8 *des);
+u8 *strcpy(const u8 *src, u8 *des);
+void strtolower(u8 *src);
+void strtoupper(u8 *src);
+void stronecase(u8 *src);
+void strsetlen(u8 *src, u8 size);
+void strinvert(u8 *src);
+void strreplace(u8 *src, u8 search, u8 replaced);
diff --git a/lib/string.c b/lib/string.c
index 3fa9764..2f88752 100755
--- a/lib/string.c
+++ b/lib/string.c
@@ -68,6 +68,7 @@ u8 *strncpy(const u8 * src, u8 * des, u32 count)
 /******************************************************************************/
 
 /* concatene 2 chaines de caractère */
+
 u8 *strcat(const u8 * src, u8 * des)
 {
 	u8 *temp = des;
@@ -76,3 +77,101 @@ u8 *strcat(const u8 * src, u8 * des)
 	while ((*des++ = *src++) != 0) ;
 	return temp;
 }
+
+/******************************************************************************/
+
+/* Met en minuscule */
+
+void strtolower(u8 * src)
+{
+	while (*src != 0) {
+        if ((*src >= 'A') && (*src <= 'Z'))
+            *src=*src+'a'-'A';
+		src++;
+    }
+}
+
+/******************************************************************************/
+
+/* Met en majuscule */
+
+void strtoupper(u8 * src)
+{
+	while (*src != 0) {
+        if ((*src >= 'a') && (*src <= 'z'))
+            *src=*src-('a'-'A');
+		src++;
+    }
+}
+
+/******************************************************************************/
+
+/* inverse la casse */
+
+void strinvertcase(u8 * src)
+{
+	while (*src != 0) {
+        if ((*src >= 'A') && (*src <= 'Z'))
+            *src=*src+'a'-'A';
+        else if ((*src >= 'a') && (*src <= 'z'))
+            *src=*src-('a'-'A');
+		src++;
+    }
+}
+
+/******************************************************************************/
+
+/* Met une majuscule et met le reste en minuscule */
+
+void stronecase(u8 * src)
+{
+    if ((*src >= 'a') && (*src <= 'z'))
+        *src=*src-('a'-'A');
+    while (*src != 0) {
+		src++;
+        if ((*src >= 'A') && (*src <= 'Z'))
+            *src=*src+'a'-'A';
+    }
+}
+
+/******************************************************************************/
+
+/* Fixe la taille de la chaine */
+
+void strsetlen(u8 * src, u8 size)
+{
+    *(src+size)='\000';
+}
+
+/******************************************************************************/
+
+/* Inverse la chaine */
+
+void strinvert(u8 *src)
+{
+    u8 *dst=src+strlen(src)-1;
+    while (src < dst) {
+        u8 char1=*dst;
+        u8 char2=*src;
+        *dst=char2;
+        *src=char1;        
+		src++;
+        dst--;
+    }
+}
+
+/******************************************************************************/
+
+/* Remplace tout les caractères rechercher par un autre */
+
+void strreplace(u8 *src, u8 search, u8 replaced)
+{
+    u8 *pos=strchr(src, search);
+    while (pos!=0)
+    {   
+        *pos=replaced;
+        pos=strchr(src, search);
+    }
+}
+
+
diff --git a/system/system.c b/system/system.c
index 443aac8..43048f2 100755
--- a/system/system.c
+++ b/system/system.c
@@ -80,6 +80,15 @@ int main(void)
 	     cpu.stepping, cpu.models, cpu.family, &cpu.detectedname,
 	     &cpu.techs);
 	ok();
+
+    u8 test[]="ceCI est UN(une) tes1\000";
+    u8 test2[]="ceCI est UN(une) tes2!\000";
+    printf(&test);
+    strreplace(&test, 'e', 'q');
+    strreplace(&test2, '(', '[');
+    printf(&test);
+    printf(&test2);
+
 	while (1) {
 		key = waitascii();
 		putchar(key);