diff --git a/README.md b/README.md
index cc835117..68985603 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,7 @@ from scratch.
    - MIDAS, the assembler.
    - DDT, debugger and HACTRN user login shell.
    - The ITS monitor (kernel).
+   - Exec DDT, standalone debugger.
    - TECO, editor.
    - DUMP, tape backup and restore.
    - PDSET, set time and date.
diff --git a/build/build.tcl b/build/build.tcl
index 88979d6c..28d68711 100644
--- a/build/build.tcl
+++ b/build/build.tcl
@@ -128,6 +128,11 @@ respond "*" ":midas system;_its\r"
 respond "MACHINE NAME =" "AI\r"
 expect ":KILL"
 
+respond "*" ":midas .;@ ddt_system;ddt\r"
+respond "cpusw" "3\r"
+respond "New One Proceed" "1\r"
+expect ":KILL"
+
 respond "*" ":midas sysbin;_.teco.;teco\r"
 expect ":KILL"
 respond "*" ":job teco\r"