Added cbegin of vector

vector/cbegin.md

@@ -0,0 +1,35 @@
+# cbgin
+
+**Description** : The function returns an iterator which is used to iterate container.
+
+Notes:
+
+1. The iterator points to the beginning of the vector.
+2. Iterator cannot modify the contents of the vector.
+
+**Example**:
+```cpp
+// Demonstrates cbegin() 
+#include <iostream>
+#include <vector>
+
+int main(){
+    //declares an empty vector
+    std::vector<int> vec;
+
+    //inserting elements in vector
+    vec.push_back(101);
+    vec.push_back(12);
+    vec.push_back(999);
+
+    //Displaying elements of  vector
+    std::cout << "Content of the vector \n";
+    for (auto it = vec.cbegin(); it != vec.end(); ++it){ 
+        std::cout << *it << '\n'; 
+    }
+    return 0;
+}
+
+```
+**[Run Code](https://rextester.com/XRFTW94461)**
+