feat(0-shell): specify how command should be implemented

subjects/0-shell/README.md

@@ -28,7 +28,7 @@ For this project you will only have to create a simple `Unix shell` where you ca
   - mkdir
   - exit
 
-> The commands need to be implemented from scratch. It is not allowed to have a Shell call that execute the required commands.
+> The commands need to be implemented from scratch. It is not allowed to execute external binaries.
 
 - You must manage the program interruption `Ctrl + D`.
 - The project has to be written in a compiled language (like C, Rust, Go or other), **interpreted languages (like Perl and others) are not allowed**.

subjects/0-shell/audit/README.md

@@ -2,7 +2,7 @@
 
 ###### Was the project written in a compiled programming language?
 
-###### Are the commands mentioned in the subject implemented from scratch, without calling any equivalent shell implementation?
+###### Are the commands mentioned in the subject implemented from scratch, without calling any external binaries?
 
 #### Functional