输入一个字符，输出该字符的前导后字符

程序运行：

 

代码：

datas segmenta                                 db ?inputPrompt                       db 'input a lowercase character:$'outputPrompt                      db 0dh,0ah,'output leading and successor character:$'outputLeadingCharacterPrompt      db 0dh,0ah,'leading   character:$'outputSuccessorCharacterPrompt    db 0dh,0ah,'successor character:$'outputErrorPrompt                 db 0dh,0ah,'input is invalid!$'
datas endsstacks segmentdb 100h dup(?)stacks endscodes segmentassume cs:codes,ds:datas,ss:stacks
main   proc  far
start:push dsmov ax,0hpush axmov ax,datas           ;初始化dsmov ds,axlea dx,inputPrompt     ;输出输入提示mov ah,9int 21hmov ah,1int 21hcmp al,'a'                    jae s1                        ;如果al>='a',则跳转s1，判断是否al<='z'jmp s3                        ;否则跳s3s1: cmp al,'z'jbe lowercaseCharacter                      ;如果al<='z',则al转大写字母jmp s3                      ;否则跳s3lowercaseCharacter:mov a,allea  dx,outputPrompt     ;输出前导字母和后继字母提示mov ah,9int 21h;lea  dx,outputLeadingCharacterPrompt     ;输出前导字母提示;mov ah,9;int 21hmov al,a                                 ;输出前导字母mov ah,0add ax,26-'a'-1mov bl,26div blmov dl,ahadd dl,'a'mov ah,2int 21hmov dl,a                                  ;输出输入字母mov ah,2int 21h;lea  dx,outputSuccessorCharacterPrompt      ;输出后继字母串提示;mov ah,9;int 21hmov al,a                                    ;输出后继字母mov ah,0add ax,26-'a'+1mov bl,26div blmov dl,ahadd dl,'a'mov ah,2int 21hjmp exit    s3:lea dx,outputErrorPrompt                        ;输出输入无效mov ah,9int 21hexit:retmain endp
codes endsend main