+forth HELLO, 'HELLO'
+ dq LIT, 'H', EMIT
+ dq LIT, 'e', EMIT
+ dq LIT, 'l', EMIT
+ dq LIT, 'l', EMIT
+ dq LIT, 'o', EMIT
+ dq LIT, '!', EMIT
+ dq NEWLINE
+ dq EXIT
+
+;; Duplicate a pair of elements.
+forth_asm PAIRDUP, '2DUP'
+ pop rbx
+ pop rax
+ push rax
+ push rbx
+ push rax
+ push rbx
+ next
+
+;; Swap the top two elements on the stack.
+forth_asm SWAP, 'SWAP'
+ pop rax
+ pop rbx
+ push rax
+ push rbx
+ next
+
+;; Remove the top element from the stack.
+forth_asm DROP, 'DROP'
+ add rsp, 8
+ next
+
+;; The INTERPRET word reads and interprets user input. It's behavior depends on
+;; the current STATE. It provides special handling for integers. (TODO)
+forth INTERPRET, 'INTERPRET'
+ ;; Read word
+ dq READ_WORD
+ dq PAIRDUP
+ ;; Stack is (word length word length).
+ dq FIND ; Try to find word
+ dq DUP_
+ dq ZBRANCH, 8 * 8 ; Check if word is found
+
+ ;; Word is found, execute it
+ dq TCFA
+ ;; Stack is (word length addr)
+ dq SWAP, DROP
+ dq SWAP, DROP
+ ;; Stack is (addr)
+ dq EXEC
+ dq EXIT
+
+ ;; No word is found, assume it is an integer literal
+ ;; Stack is (word length addr)
+ dq DROP
+ dq PARSE_NUMBER
+ dq EXIT
+
+;; .U prints the value on the stack as an unsigned integer in hexadecimal.
+forth_asm DOTU, '.U'
+ mov [.length], 0
+ mov [.printed_length], 1
+ pop rax ; RAX = value to print
+ push rsi ; Save value of RSI
+
+ ;; We start by constructing the buffer to print in reverse
+
+.loop:
+ mov rdx, 0
+ mov rbx, $10
+ div rbx ; Put remainer in RDX and quotient in RAX
+
+ ;; Place the appropriate character in the buffer
+ mov rsi, .chars
+ add rsi, rdx
+ mov bl, [rsi]
+ mov rdi, .rbuffer
+ add rdi, [.length]
+ mov [rdi], bl
+ inc [.length]
+
+ ;; .printed_length is the number of characters that we ulitmately want to
+ ;; print. If we have printed a non-zero character, then we should update
+ ;; .printed_length.
+ cmp bl, '0'
+ je .skip_updating_real_length
+ mov rbx, [.length]
+ mov [.printed_length], rbx
+.skip_updating_real_length:
+
+ cmp [.length], 16
+ jle .loop
+
+ ;; Flip buffer around, since it is currently reversed
+ mov rcx, [.printed_length]
+.flip:
+ mov rsi, .rbuffer
+ add rsi, rcx
+ dec rsi
+ mov al, [rsi]
+
+ mov rdi, .buffer
+ add rdi, [.printed_length]
+ sub rdi, rcx
+ mov [rdi], al
+
+ loop .flip
+
+ ;; Print the buffer
+ mov rax, 1
+ mov rdi, 1
+ mov rsi, .buffer
+ mov rdx, [.printed_length]
+ syscall
+
+ ;; Restore RSI and continue execution
+ pop rsi
+ next
+
+;; Takes a value and an address, and stores the value at the given address.
+forth_asm PUT, '!'
+ pop rbx ; Address
+ pop rax ; Value
+ mov [rbx], rax
+ next
+
+;; Takes an address and returns the value at the given address.
+forth_asm GET, '@'
+ pop rax
+ mov rax, [rax]
+ push rax
+ next
+
+;; Get the location of the STATE variable. It can be set with '!' and read with
+;; '@'.
+forth STATE, 'STATE'
+ dq LIT, var_STATE
+ dq EXIT
+
+;; Get the location of the LATEST variable. It can be set with '!' and read with
+;; '@'.
+forth LATEST, 'LATEST'
+ dq LIT, latest_entry
+ dq EXIT
+
+;; Get the location at which compiled words are expected to be added. This
+;; pointer is usually modified automatically when calling ',', but we can also
+;; read it manually with 'HERE'.
+forth HERE, 'HERE'
+ dq LIT, here
+ dq EXIT
+
+forth MAIN, 'MAIN'