diff --git a/C Crash Course/13 String/Prelesson/code/mystrcmp/VSstrcmp.c b/C Crash Course/13 String/Prelesson/code/mystrcmp/VSstrcmp.c
new file mode 100644
index 0000000..67a52e3
--- /dev/null
+++ b/C Crash Course/13 String/Prelesson/code/mystrcmp/VSstrcmp.c	
@@ -0,0 +1,29 @@
+//这是我能理解的格式
+int mystrcmp(char* str1, char* str2) {
+
+	int ret = 0;
+
+	while ((ret = ((unsigned char)*str1 - (unsigned char)*str2)) == 0 && *str1) {
+		++str1, ++str2;
+	}
+
+	return ret;
+}
+
+
+//原版在这里
+int __cdecl strcmp(
+	const char* src,
+	const char* dst
+)
+{
+	int ret = 0;
+
+	while ((ret = *(unsigned char*)src - *(unsigned char*)dst) == 0 && *dst)
+	{
+		++src, ++dst;
+	}
+	
+	//这里不太理解，那个大神理解了可以给我讲一下，谢谢
+	return ((-ret) < 0) - (ret < 0); // (if positive) - (if negative) generates branchless code
+}
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diff --git a/C Crash Course/13 String/Prelesson/code/mystrcmp/main.c b/C Crash Course/13 String/Prelesson/code/mystrcmp/main.c
new file mode 100644
index 0000000..06d8e64
--- /dev/null
+++ b/C Crash Course/13 String/Prelesson/code/mystrcmp/main.c	
@@ -0,0 +1,11 @@
+
+
+int main() {
+
+	char* str1 = "Hello ";
+	char* str2 = "Hello";
+
+	printf("%d\n", mystrcmp(str1, str2));
+
+	return 0;
+}
\ No newline at end of file
diff --git a/C Crash Course/13 String/Prelesson/code/mystrcmp/mystrcmp.c b/C Crash Course/13 String/Prelesson/code/mystrcmp/mystrcmp.c
new file mode 100644
index 0000000..22596c1
--- /dev/null
+++ b/C Crash Course/13 String/Prelesson/code/mystrcmp/mystrcmp.c	
@@ -0,0 +1,7 @@
+int mystrcmp(char* str1, char* str2) {
+
+	while (*str1 == *str2 && *str1)
+		++str1, ++str2;
+
+	return (*str1 - *str2);
+}
\ No newline at end of file