diff --git a/README.md b/README.md
index a879348..9ab91aa 100644
--- a/README.md
+++ b/README.md
@@ -11,21 +11,21 @@ $ cat helloworld.fs | ./plank
 
 # Builtin Words
 
-| code | name     | semantics                                 |
-|:----:|:---------|:------------------------------------------|
-| Q    | quit     | ( -- ) Exit the process                   |
-| C    | cell     | ( -- n ) The size of Cells                |
-| h    | here     | ( -- addr ) The address of 'here' cell    |
-| l    | latest   | ( -- addr ) The address of 'latest' cell  |
-| k    | key      | ( -- n ) Read character                   |
-| t    | type     | ( n -- ) Print character                  |
-| j    | jump     | ( -- ) Unconditional branch.              |
-| J    | 0jump    | ( a -- ) Jump if a == 0.                  |
-| f    | find     | ( c -- xt ) Get execution token of c      |
-| x    | execute  | ( xt -- ... ) Run the execution token     |
-| @    | fetch    | ( addr -- a ) Load value from addr        |
-| !    | store    | ( a addr -- ) Store value to addr         |
-| ?    | cfetch   | ( addr -- c ) Load byte from addr         |
-| $    | cstore   | ( c addr -- ) Store byte to addr          |
-| d    | dfetch   | ( -- addr ) Get data stack pointer        |
-| D    | dstore   | ( addr -- ) Set data stack pointer        |
+| code | name     | stack effect  | semantics                      |
+|:----:|:---------|:--------------|:-------------------------------|
+| Q    | quit     | ( -- )        | Exit the process               |
+| C    | cell     | ( -- n )      | The size of Cells              |
+| h    | here     | ( -- addr )   | The address of 'here' cell     |
+| l    | latest   | ( -- addr )   | The address of 'latest' cell   |
+| k    | key      | ( -- n )      | Read character                 |
+| t    | type     | ( n -- )      | Print character                |
+| j    | jump     | ( -- )        | Unconditional branch.          |
+| J    | 0jump    | ( a -- )      | Jump if a == 0.                |
+| f    | find     | ( c -- xt )   | Get execution token of c       |
+| x    | execute  | ( xt -- ... ) | Run the execution token        |
+| @    | fetch    | ( addr -- a ) | Load value from addr           |
+| !    | store    | ( a addr -- ) | Store value to addr            |
+| ?    | cfetch   | ( addr -- c ) | Load byte from addr            |
+| $    | cstore   | ( c addr -- ) | Store byte to addr             |
+| d    | dfetch   | ( -- addr )   | Get data stack pointer         |
+| D    | dstore   | ( addr -- )   | Set data stack pointer         |