How to resolve the algorithm Compare length of two strings step by step in the Z80 Assembly programming language

Published on 12 May 2024 09:40 PM
#Z80 assembly

How to resolve the algorithm Compare length of two strings step by step in the Z80 Assembly programming language

Table of Contents

Problem Statement

Given two strings of different length, determine which string is longer or shorter. Print both strings and their length, one on each line. Print the longer one first. Measure the length of your string in terms of bytes or characters, as appropriate for your language. If your language doesn't have an operator for measuring the length of a string, note it. Given more than two strings: list = ["abcd","123456789","abcdef","1234567"] Show the strings in descending length order.

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Step by Step solution about How to resolve the algorithm Compare length of two strings step by step in the Z80 Assembly programming language

Source code in the z80 programming language

Terminator equ 0      ;null terminator
PrintChar equ &BB5A   ;Amstrad CPC BIOS call, prints accumulator to screen as an ASCII character.

        org &8000

	ld hl,String1
	ld de,String2
	call CompareStringLengths
	
	jp nc, Print_HL_First
		ex de,hl
Print_HL_First:
	push bc
		push hl
			call PrintString
		pop hl
		push hl
			ld a,' '
			call PrintChar
			call getStringLength
			ld a,b
			call ShowHex_NoLeadingZeroes
			call NewLine
		pop hl
	pop bc
	
	ex de,hl
	push bc
		push hl
			call PrintString
		pop hl
		push hl
			ld a,' '
			call PrintChar
			call getStringLength
			ld a,b
			call ShowHex_NoLeadingZeroes
			call NewLine
		pop hl
	pop bc	
ReturnToBasic:
	RET

String1:
	byte "Hello",Terminator
String2:
	byte "Goodbye",Terminator

;;;;;; RELEVANT SUBROUTINES - PRINTSTRING AND NEWLINE CREATED BY KEITH S. OF CHIBIAKUMAS
CompareStringLengths:
	;HL = string 1
	;DE = string 2
	;CLOBBERS A,B,C
	push hl
	push de
	ex de,hl
	call GetStringLength
	ld b,c
	
	ex de,hl
	call GetStringLength
	ld a,b
	cp c
	pop de
	pop hl
	ret
	;returns carry set if HL < DE, zero set if equal, zero & carry clear if HL >= DE
	;returns len(DE) in C, and len(HL) in B.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
GetStringLength:
		ld b,0
loop_getStringLength:
		ld a,(hl)
		cp Terminator
		ret z
		inc hl
		inc b
		jr loop_getStringLength
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
NewLine:
	push af
	ld a,13		;Carriage return
	call PrintChar
	ld a,10		;Line Feed 
	call PrintChar
	pop af
	ret
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
PrintString:
	ld a,(hl)	
	cp Terminator
	ret z
	inc hl
	call PrintChar
	jr PrintString
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
ShowHex_NoLeadingZeroes:
;useful for printing values where leading zeroes don't make sense,
; 	such as money etc.
	push af
		and %11110000
		ifdef gbz80      ;game boy 
			swap a
		else             ;zilog z80
			rrca
			rrca
			rrca
			rrca
		endif
		or a
		call nz,PrintHexChar
		;if top nibble of A is zero, don't print it.
	pop af
	and %00001111
	or a
	ret z	;if bottom nibble of A is zero, don't print it!
	jp PrintHexChar
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
PrintHexChar:
	or a	  ;Clear Carry Flag
	daa
	add a,&F0
	adc a,&40 ;This sequence converts a 4-bit hex digit to its ASCII equivalent.
	jp PrintChar

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