diff --git a/first-interpreter/readme.md b/first-interpreter/readme.md
index d267de7..fdfa82c 100644
--- a/first-interpreter/readme.md
+++ b/first-interpreter/readme.md
@@ -4,6 +4,14 @@ Code for a very simple interpreter.
 
 Accompanying blogpost: https://alloca.space/blog/my-first-interpreter.html
 
+## Build and run
+
+Requires: gcc, make
+
+```sh
+make run
+```
+
 ## Example Program
 
 ```go
@@ -18,10 +26,12 @@ while counter {
 print(sum)
 ```
 
-## Build and run
+## Structure
 
-Requires: gcc, make
-
-```sh
-make run
-```
+- `main.c` - entry point. Reads user input and calls the interpreter
+- `run.c` - glue code. invokes the interpreter stages.
+- `ast.h` - AST definitions
+- `lex.h` - Tokens definitions
+- `lex.c` - Stage 1 - Lexing: Text -> Tokens
+- `parsing.c` - Stage 2 - Parsing: Tokens -> Ast
+- `execute.c` - Stage 3 - Execute: Ast -> Output