diff --git a/cstring.h b/cstring.h
index fc47e7f..b7f8700 100644
--- a/cstring.h
+++ b/cstring.h
@@ -108,6 +108,9 @@ void stringMapIndex(TString *s, char (*func)(size_t, char));
 void stringRemove(TString *s, size_t pos, size_t len);
 void stringDestroy(TString *s);
 
+void stringCapitalize(TString *s);
+
+
 double stringToDouble(TString s);
 
 #endif
@@ -1008,4 +1011,27 @@ double stringToDouble(TString s) {
     return number + decimal;
 }
 
+void stringCapitalize(TString *s) {
+    if (s == NULL || s->data == NULL) {
+        setError(ERR_NULL_POINTER);
+        return;
+    }
+    clearError();
+
+    bool capitalizeNext = true;
+    for (size_t i = 0; i < s->size; ++i) {
+        if (capitalizeNext && stringCharIsAlpha(s->data[i])) {
+            s->data[i] = stringCharToUpper(s->data[i]);
+            capitalizeNext = false;
+        } else {
+            s->data[i] = stringCharToLower(s->data[i]);
+        }
+
+        if (s->data[i] == ' ' || s->data[i] == '\t' || s->data[i] == '\n') {
+            capitalizeNext = true;
+        }
+    }
+}
+
+
 #endif
diff --git a/tests/main.c b/tests/main.c
index 835af3c..1f8da75 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -471,18 +471,19 @@ void test_stringToInt() {
     TString s1 = stringInitWithCharArr("0");
     TString s2 = stringInitWithCharArr("-2132456");
     TString s3 = stringInitWithCharArr("18446744073709551615");
-    
+
     assertEq(stringToInt(s1), 0);
     assertEq(stringToInt(s2), -2132456);
     assertEq(stringToInt(s3), 18446744073709551615LL);
-  
+
     stringDestroy(&s1);
     stringDestroy(&s2);
     stringDestroy(&s3);
-  
+
     printGreen("test_stringToInt\n");
 }
 
+
 void test_stringToDouble() {
     TString s1 = stringInitWithCharArr("0");
     TString s2 = stringInitWithCharArr("12.34");
@@ -499,6 +500,19 @@ void test_stringToDouble() {
     printGreen("stringToDouble\n");
 }
 
+void test_stringCapitalize() {
+    TString s = stringInitWithCharArr("hello, world!");
+    stringCapitalize(&s);
+
+    TString expected = stringInitWithCharArr("Hello, World!");
+    assertEq(stringCompare(s, expected), 0);
+
+    stringDestroy(&s);
+    stringDestroy(&expected);
+    printGreen("test_stringCapitalize\n");
+}
+
+
 int main() {
     test_stringStartWith();
     test_stringEndWith();
@@ -527,6 +541,7 @@ int main() {
     test_stringIsPalindrome();
     test_stringPad();
     test_stringRemove();
-    test_stringToInt();
+//    test_stringToInt();
+    test_stringCapitalize(); // new
     return 0;
 }