operand type does not match

[access1011]

Im making a progam that ask for a value. The program than calculates values into a formula.
My problem MOV U, AX. It generates a error (OPERAND TYPES DO NOT MATCH)

here is my code

		page	58, 132
		name	RUN
		title	RUN (Executes a program specified on the cmd line).
		



		include	consts.a
		include stdin.a
		include stdout.a
		include misc.a
		include memory.a
		include	strings.a

		.list
                include                 stdlib.a
                includelib              stdlib.lib
                

dseg            segment public

I db 44
testtest db ?
u               db    ?
v               db    ?
w               db    ?
x               db    ?
y               db    ?


dseg            ends
cseg segment public 'code'



cseg ends




CSEG		segment public 'CODE'
		assume	cs:cseg, ds:cseg 


; Variables used by this program.  Okay, so I'm lazy and should have put
; them into their own segment.  However, you will not that I do not assume
; that these variables are in the code segment.
geti            equ <call _geti>
_geti           proc
                push    es
                push    di

                getsm
                atoi
                free

                pop     di
                pop     es
                ret
_geti           endp



Main		proc
		mov ax, dseg
		mov ds, ax
		mov es, ax
		meminit

; If you want to do something before the execution of the command-line
; specified program, here is a good place to do it:





print
                db    "Abitrary expression program",cr,lf
                db    "---------------------------",cr,lf
                db    lf
                db    "Enter a value for u: ",0

               geti
                mov    u, ax

;I HAVE NOT DONE THE FORMULA YET, BUT I WILL
                





              
                
                
               
                
                
		


; Okay, if you have any great deeds to do after the program, this is a
; good place to put such stuff.




; Return control to MS-DOS

Quit:		ExitPgm

Main		endp


cseg		ends



sseg		segment	para stack 'stack'
		dw	1024 dup (0)
endstk		dw	?
sseg		ends

; Seg aside some room for the heap.

zzzzzzseg	segment	para public 'zzzzzzseg'
		public	Heap
Heap		db	200h dup (?)
zzzzzzseg	ends

		end	Main

Im using TASM assembler. Also, Why can i not use WORD in my DSEG, I have to use DB or it will give me UNDEFINED SYMBOL: U.

Also.. the "mov u, ax" can be fixed with "mov WORD PTR U, ax"....but than i get (CANT ADDRESS WITH CURRENTLY ASSUMED SEGMENT REGISTERS.