diff --git a/desk.acc/a2d.inc b/desk.acc/a2d.inc
index 9371e33..bce7d1f 100644
--- a/desk.acc/a2d.inc
+++ b/desk.acc/a2d.inc
@@ -208,8 +208,15 @@ A2D_UNK_2B      := $2B          ; Unknown - possibly "reset drawing state"
         ;; $2C used in DeskTop but not DAs
         ;; (input length 0 bytes)
 
-A2D_UNK_2D      := $2D          ; Unknown - used in calculator
+A2D_SET_INPUT   := $2D          ; Set pending input state (mouse or keyboard)
         ;; (input length 5 bytes)
+        ;; .byte state          (A2D_INPUT_*)
+        ;; if state is A2D_INPUT_KEY:
+        ;;   .byte key          (ASCII code; high bit clear)
+        ;;   .byte modifiers    (0=none, 1=open-apple, 2=closed-apple, 3=both)
+        ;; if state otherwise:
+        ;;   .word xcoord
+        ;;   .word ycoord
 
 A2D_CREATE_WINDOW := $38
         ;; .byte id
diff --git a/desk.acc/calculator.s b/desk.acc/calculator.s
index 19b7083..3bea513 100644
--- a/desk.acc/calculator.s
+++ b/desk.acc/calculator.s
@@ -799,8 +799,8 @@ init:   sta     ALTZPON
         A2D_CALL $2B                          ; reset drawing state?
         lda     #$01
         sta     input_state_params::state
-        A2D_CALL $2D, input_state_params ; ???
-        A2D_CALL A2D_GET_INPUT, input_state_params ; ???
+        A2D_CALL A2D_SET_INPUT, input_state_params
+        A2D_CALL A2D_GET_INPUT, input_state_params
         lda     ROMIN2
         jsr     reset_buffer2
         lda     #window_id