added ComputerArchitecture in free-courses-en.md (#7320)

courses/free-courses-en.md

@@ -15,6 +15,7 @@
 * [Clojure](#clojure)
 * [Cloud Computing](#cloud-computing)
 * [Compilers](#compilers)
+* [Computer Organization and Architecture](#computer-organization-and-architecture)
 * [Computer Science](#computer-science)
 * [CUDA](#cuda)
 * [Dart](#dart)
@@ -271,6 +272,11 @@
 * [Stanford's Compilers](https://www.edx.org/course/compilers)
 
 
+### Computer Organization and Architecture
+
+* [Computer Organization & Architecture (COA)](https://www.youtube.com/playlist?list=PLBlnK6fEyqRgLLlzdgiTUKULKJPYc0A4q) - Neso Academy (YouTube)
+
+
 ### Computer Science
 
 * [Berkeley's CS  61A: Taught using SICP](https://archive.org/details/ucberkeley-webcast-PL3E89002AA9B9879E?tab=collection)