8086 ALP: vowels and consonants separately

Method: read the string with function 0Ah. The procedure SHOWCLS scans the string and displays only the characters whose class (returned by CLASSIFY) equals the class in BH: 1 for vowels, 2 for consonants. It is called twice, so vowels appear on the first line and consonants on the second. Spaces, digits and symbols are ignored.

.MODEL SMALL
.STACK 100H

DISPSTR MACRO MSG            ; display a '$'-terminated string
        LEA  DX,MSG
        MOV  AH,09H
        INT  21H
        ENDM

CLRSCR  MACRO                ; clear screen and home the cursor
        MOV  AX,0600H        ; scroll whole window (AL=0 -> blank it)
        MOV  BH,07H          ; normal attribute
        MOV  CX,0000H        ; upper-left corner (row 0, col 0)
        MOV  DX,184FH        ; lower-right corner (row 24, col 79)
        INT  10H
        MOV  AH,02H          ; set cursor position
        MOV  BH,00H          ; page 0
        MOV  DX,0000H        ; row 0, col 0
        INT  10H
        ENDM

.DATA
    MSG1  DB 'Enter a string: $'
    MSGV  DB 13,10,'Vowels     : $'
    MSGC  DB 13,10,'Consonants : $'
    BUF   DB 80, ?, 80 DUP(0)   ; DOS buffered-input area (max, actual, chars)
    CRLF  DB 13,10,'$'

.CODE
MAIN PROC
    MOV  AX,@DATA
    MOV  DS,AX

    DISPSTR MSG1           ; prompt
    LEA  DX,BUF            ; read the string with DOS function 0Ah
    MOV  AH,0AH
    INT  21H

    DISPSTR MSGV
    MOV  BH,1              ; class 1 = vowels
    CALL SHOWCLS
    DISPSTR MSGC
    MOV  BH,2              ; class 2 = consonants
    CALL SHOWCLS
    MOV  AH,4CH            ; return to DOS
    INT  21H
MAIN ENDP

; ---- display characters of the string whose class = BH
SHOWCLS PROC
    LEA  SI,BUF+2
    MOV  CL,BUF+1
    MOV  CH,0
    JCXZ SCEND
SC1:MOV  DL,[SI]
    CALL CLASSIFY          ; AL = class of DL
    CMP  AL,BH
    JNE  SC2
    MOV  AH,02H            ; display DL
    INT  21H
SC2:INC  SI
    LOOP SC1
SCEND:RET
SHOWCLS ENDP

; ---- classify the character in DL
;      returns AL = 1 vowel, 2 consonant, 0 not a letter (DL unchanged)
CLASSIFY PROC
    MOV  AL,DL
    OR   AL,20H            ; fold to lower case (valid for letters)
    CMP  AL,'a'
    JB   NOTLET
    CMP  AL,'z'
    JA   NOTLET
    CMP  AL,'a'
    JE   VOW
    CMP  AL,'e'
    JE   VOW
    CMP  AL,'i'
    JE   VOW
    CMP  AL,'o'
    JE   VOW
    CMP  AL,'u'
    JE   VOW
    MOV  AL,2              ; consonant
    RET
VOW:MOV  AL,1              ; vowel
    RET
NOTLET:MOV AL,0            ; not a letter
    RET
CLASSIFY ENDP

END MAIN

Example: input Hello World → Vowels: eoo, Consonants: HllWrld.