diff --git a/documentation.frt b/documentation.frt
index c8ea719..9f05e85 100644
--- a/documentation.frt
+++ b/documentation.frt
@@ -1,14 +1,162 @@
-' dup g" 
-( a - a a )
-Duplicate the cell on top of the stack.
+' include g" 
+Include the file content in the content of current file.
+" doc-word
+
+' file-print g"
+( fd str -- ) 
+Print file.
+" doc-word
+                                                                        
+' file-close g" 
+Close file.
+" doc-word
+
+' file-open-read g" 
+( str -- )
+Open file with name str as read-only.
+" doc-word
+                                                                            
+' file-open-append g" 
+( str -- )
+Open file with name str for reading and writing. If file does not exist create it as a regular file.
+" doc-word
+
+' file-create g" 
+( str -- )
+Create a regular file with name specified by the string on top of the stack and the following flags: O_RDWR, O_CREAT, O_TRUNC.
+" doc-word
+                                                                      
+' sys-close g" 
+System call to close a file. The exit code is on the top of the stack.
+" doc-word
+
+' sys-close-no g" 
+Place the number of sys_close system call on the top of the stack.
+" doc-word
+
+' sys-open g" 
+System call to open a file. The exit code is on the top of the stack.
+" doc-word
+
+' sys-open-no g" 
+Place the number of sys_open system call on the top of the stack.
+" doc-word
+                                                                 
+' O_RDONLY g" 
+File access mode flag for opening file as read-only.
+" doc-word
+
+' O_WRONLY g" 
+File access mode flag for opening file as write-only.
+" doc-word
+
+' O_RDWR g" 
+File access mode flag for opening file as read/write.
+" doc-word
+
+' O_TRUNC g" 
+File creation flag.
+If the file already exists and is a regular file and the access mode allows writing (i.e., is O_RDWR or O_WRONLY) it will be truncated to length 0.
+" doc-word
+
+' O_CREAT g" 
+File creation flag.
+If file does not exist create it as a regular file.
+" doc-word
+
+' O_APPEND g" 
+File creation flag.
+The file is opened in append mode. Before each write operation, the file offset is positioned at the end of the file.
+" doc-word
+
+' 0x g" 
+( -- hex )
+Place a hexadecimal literal's decimal representation on top of the stack. If it is not a hexadecimal literal place 0.
+" doc-word 
+
+' O8x g" 
+( -- oct )
+Place an octal literal on top of the stack. If it is not an octal literal place 0.
+" doc-word 
+
+' read-oct-digit g" 
+( -- oct )
+Read an octal digit add place it on top of the stack; otherwise place -1.
+" doc-word 
+
+' read-hex-digit g" 
+( -- hex )
+Read a hexadecimal digit add place its decimal representation on top of the stack; otherwise place -1.
+" doc-word 
+
+' read-digit g"
+( -- dec ) 
+Read a decimal digit and place it on top of the stack; otherwise place -1.
+" doc-word 
+  
+' ." g" 
+Print the words up to the delimiting double-quote.
+" doc-word 
+                                                                                             
+' g" g" 
+Create a documentation of the dictionary word whose XT is on top of the stack.
+Description of the word goes up to the delimiting double-quote followed by the word 'doc-word'.
+" doc-word 
+
+' TAB g" 
+( -- char ) 
+Place TAB ASCII code on top of the stack.
+" doc-word 
+
+' QUOTE g" 
+( -- char ) 
+Place double quotes ASCII code on top of the stack.
+" doc-word 
+
+' cr g" 
+Start a new line.
 " doc-word 
 
-' drop g"
-( a -- )
-Drop the topmost element of the stack
+' readce g" 
+( -- char ) 
+Read character and place its ASCII code on top of the stack.
+Place 0 for control characters except new line character \n.
+" doc-word 
+
+' .' g"
+( -- char ) 
+Place character ASCII code on top of the stack.
+" doc-word 
+
+' compnumber g" 
+Compute number in compilation mode.
+" doc-word 
+
+' compiling g"
+( -- state ) 
+Place on top of the stack the current Forth state:
+0 - interpretation mode
+1 - compilation mode
+" doc-word 
+
+' in-range g" 
+( num from to -- 1/0 )
+Check if number is in given range. Place on top of the stack 1 if it is; otherwise place 0. 
+" doc-word 
+                                                                
+' case g" 
+Execute the block of code associated with the case clause. Case clause mathes the value of the topmost element of the stack.
+" doc-word
+
+' of g" 
+Match the beginning of the block of code for a case clause.
 " doc-word
 
-' swap g" 
-( a b -- b a )
-Swap two topmost elements of the stack
+' endof g" 
+Match the end of the block of code for a case clause.
 " doc-word
+
+' endcase g" 
+Match the end of case statement.
+" doc-word 
+