Print itself: Difference between revisions
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$ wren self_print.wren
</pre>
{{header|Z80 Assembly}}
This program prints its bytecode as text to the Amstrad CPC terminal. The program is run by typing <code>call &1000</code> to the screen.
<lang z80>org &1001
ld hl,&1001 ;&1000 won't work since that contains &00.
ld e,&ff ;&00 is the terminator so we can't use zero as an immediate directly
inc e ;Must abuse 8-bit underflow to get it.
loop:
ld a,(hl)
cp e
jp z,ProgramEnd
call UnpackNibbles
ld a,b
cp &0A
jr c,noCorrectHex_B
add &07
noCorrectHex_B:
add &30
call &bb5a
ld a,c
cp &0A
jr c,noCorrectHex_C
add &07
noCorrectHex_C:
add &30
call &bb5a
inc hl
jp loop
ProgramEnd:
ld a,&30
call &bb5a
ld a,&30
call &bb5a
ret ;return to basic
UnpackNibbles:
;splits a into its component nibbles, storing high nibble in B and low in C.
push af
and &0f
ld c,a
pop af
and &f0
rrca
rrca
rrca
rrca
ld b,a
ret
db 0 ;null terminator. No instructions or operands above compile to &00. </lang>
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