Comparing Similar Code on Different Processors
             ==============================================

Z80               6502              ARM               pdp11
===               ====              ===               =====

Print string, not preserving registers or memory
------------------------------------------------
HL=>string        XY=>string        R0=>string        R0=>string
                  255 bytes max

.PrText           .PrText           .PrText           .PrText
                  STX zp+0
                  STY zp+1
                  LDY #0
.Loop             .Loop             .Loop             .Loop
LD   A,(HL)       LDA (zp),Y        LDRBS r0,[r1,#1]  MOVB (r1)+,r0
INC  HL
AND  A
RET  Z            BEQ PrTextEnd                       BEQ  PrTextEnd
CALL OSWRCH       JSR OSWRCH        SWINE "OS_WRCH"   EMT  "OSWRCH"
                  INY
JR   Loop         BNE Loop          BNE   Loop        BRA  Loop
                  .PrTextEnd                          .PtTextEnd
                  RTS               MOV   pc,link     RTS  pc
--                --                --                --
 9                17                16                10

Print string, preserving registers and memory, returning address after of end of string
---------------------------------------------------------------------------------------
HL=>string        XY=>string        R0=>string        R0=>string
                  255 bytes max

.PrText           .PrText           .PrText           .PrText
PUSH AF           PHA               STMFD !sp,{r0}    MOVB r0,-(sp)
                  LDA zp+0
                  PHA
                  LDA zp+1
                  PHA
                  STX zp+0
                  STY zp+1
                  LDY #0  
.Loop             .Loop             .Loop             .Loop
LD   A,(HL)       LDA (zp),Y        LDRBS r0,[r1,#1]  MOVB (r1)+,r0
INC  HL
AND  A
JR   Z,PrTextEnd  BEQ PrTextEnd                       BEQ  PrTextEnd
CALL OSWRCH       JSR OSWRCH        SWINE "OS_WRCH"   EMT  "OSWRCH"
                  INY
JR   Loop         BNE Loop          BNE   Loop        BRA  Loop
.PrTextEnd        .PrTextEnd                          .PrTextEnd
                  TYA
                  SEC
                  ADC zp+0
                  TAX
                  LDA #0
                  ADC zp+1
                  TAY
                  PLA
                  STA zp+1
                  PLA
                  STA zp+0
POP  AF           PLA               LDMFD sp!,{r0}    MOV  (sp)+,r0
RET               RTS               MOV   pc,link     RTS  pc
--                --                --                --
13                41                24                14