diff --git a/README.md b/README.md
index eb36cfb..0e8f6ca 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # PlanckForth: Bootstrapping Forth from Handwritten ELF Binary
 
-This project aims to bootstrap a Forth interpreter from hand-written tiny ELF binary, for fun.
-No practical use.
+This project aims to bootstrap a Forth interpreter from hand-written tiny ELF binary.
+This is just for fun. No practical use.
 
 ## How to build
 
@@ -50,45 +50,45 @@ $ ./planck < bootstrap.fs runtests.fs
 
 # Builtin Words
 
-| code | name      | stack effect    | semantics                    |
-|:----:|:----------|:----------------|:-----------------------------|
-| Q    | quit      | ( n -- )        | Exit the process             |
-| C    | cell      | ( -- n )        | The size of Cells            |
-| h    | &here     | ( -- a-addr )   | The address of 'here' cell   |
-| l    | &latest   | ( -- a-addr )   | The address of 'latest' cell |
-| k    | key       | ( -- c )        | Read character               |
-| t    | type      | ( c -- )        | Print character              |
-| j    | jump      | ( -- )          | Unconditional branch         |
-| J    | 0jump     | ( n -- )        | Jump if a == 0               |
-| f    | find      | ( c -- xt )     | Get execution token of c     |
-| x    | execute   | ( xt -- ... )   | Run the execution token      |
-| @    | fetch     | ( a-addr -- w ) | Load value from addr         |
-| !    | store     | ( w a-addr -- ) | Store value to addr          |
-| ?    | cfetch    | ( c-addr -- c ) | Load byte from addr          |
-| $    | cstore    | ( c c-addr -- ) | Store byte to addr           |
-| d    | dfetch    | ( -- a-addr )   | Get data stack pointer       |
-| D    | dstore    | ( a-addr -- )   | Set data stack pointer       |
-| r    | rfetch    | ( -- a-addr )   | Get return stack pointer     |
-| R    | rstore    | ( a-addr -- )   | Set return stack pointer     |
-| i    | docol     | ( -- a-addr )   | Get the interpreter function |
-| e    | exit      | ( -- )          | Exit current function        |
-| L    | lit       | ( -- n )        | Load immediate               |
-| S    | litstring | ( -- c-addr )   | Load string literal          |
-| +    | add       | ( a b -- c )    | c = (a + b)                  |
-| -    | sub       | ( a b -- c )    | c = (a - b)                  |
-| *    | mul       | ( a b -- c )    | c = (a * b)                  |
-| /    | divmod    | ( a b -- c d )  | c = (a mod b), d = (a / b)   |
-| &    | and       | ( a b -- c )    | c = (a & b)                  |
-| \|   | or        | ( a b -- c )    | c = (a \| b)                 |
-| ^    | xor       | ( a b -- c )    | c = (a ^ b)                  |
-| <    | less      | ( a b -- c )    | c = (a < b)                  |
-| u    | uless     | ( a b -- c )    | c = (a unsigned< b)          |
-| =    | equal     | ( a b -- c )    | c = (a == b)                 |
-| {    | shl       | ( a b -- c )    | c = a << b (logical)         |
-| }    | shr       | ( a b -- c )    | c = a >> b (logical)         |
-| )    | sar       | ( a b -- c )    | c = a >> b (arithmetic)      |
-| v    | argv      | ( -- a-addr u ) | argv and argc                |
-| V    | version   | ( -- c-addr )   | Runtime infomation string    |
+| code | name      | stack effect    | semantics                               |
+|:----:|:----------|:----------------|:----------------------------------------|
+| Q    | quit      | ( n -- )        | Exit the process                        |
+| C    | cell      | ( -- n )        | The size of Cells                       |
+| h    | &here     | ( -- a-addr )   | The address of 'here' cell              |
+| l    | &latest   | ( -- a-addr )   | The address of 'latest' cell            |
+| k    | key       | ( -- c )        | Read character                          |
+| t    | type      | ( c -- )        | Print character                         |
+| j    | jump      | ( -- )          | Unconditional branch                    |
+| J    | 0jump     | ( n -- )        | Jump if a == 0                          |
+| f    | find      | ( c -- xt )     | Get execution token of c                |
+| x    | execute   | ( xt -- ... )   | Run the execution token                 |
+| @    | fetch     | ( a-addr -- w ) | Load value from addr                    |
+| !    | store     | ( w a-addr -- ) | Store value to addr                     |
+| ?    | cfetch    | ( c-addr -- c ) | Load byte from addr with sign extension |
+| $    | cstore    | ( c c-addr -- ) | Store byte to addr                      |
+| d    | dfetch    | ( -- a-addr )   | Get data stack pointer                  |
+| D    | dstore    | ( a-addr -- )   | Set data stack pointer                  |
+| r    | rfetch    | ( -- a-addr )   | Get return stack pointer                |
+| R    | rstore    | ( a-addr -- )   | Set return stack pointer                |
+| i    | docol     | ( -- a-addr )   | Get the code pointer of interpreter     |
+| e    | exit      | ( -- )          | Exit current function                   |
+| L    | lit       | ( -- n )        | Load immediate                          |
+| S    | litstring | ( -- c-addr )   | Load string literal                     |
+| +    | add       | ( a b -- c )    | c = (a + b)                             |
+| -    | sub       | ( a b -- c )    | c = (a - b)                             |
+| *    | mul       | ( a b -- c )    | c = (a * b)                             |
+| /    | divmod    | ( a b -- c d )  | c = (a mod b), d = (a / b)              |
+| &    | and       | ( a b -- c )    | c = (a & b)                             |
+| \|   | or        | ( a b -- c )    | c = (a \| b)                            |
+| ^    | xor       | ( a b -- c )    | c = (a ^ b)                             |
+| <    | less      | ( a b -- c )    | c = (a < b)                             |
+| u    | uless     | ( a b -- c )    | c = (a unsigned< b)                     |
+| =    | equal     | ( a b -- c )    | c = (a == b)                            |
+| {    | shl       | ( a b -- c )    | c = a << b (logical)                    |
+| }    | shr       | ( a b -- c )    | c = a >> b (logical)                    |
+| )    | sar       | ( a b -- c )    | c = a >> b (arithmetic)                 |
+| v    | argv      | ( -- a-addr u ) | argv and argc                           |
+| V    | version   | ( -- c-addr )   | Runtime infomation string               |
 
 # Implementations