--- title: "8086 ALP: words on separate lines, centered" subject: "Microprocessor" chapter: 3 key: "semester_4/microprocessor:alp-8086-words-separate-lines-center" source: https://www.bctengineer.com/q/semester_4/microprocessor/alp-8086-words-separate-lines-center site: BCT Engineering --- # 8086 ALP: words on separate lines, centered Microprocessor · Chapter 3: Programming with 8086 Microprocessor - Asked in: 2072 Magh, 8 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/microprocessor/alp-8086-words-separate-lines-center - Whole chapter: https://www.bctengineer.com/md/semester_4/microprocessor/chapter-3 ## Question Write a program in 8086 to read a string and display each word in a separate line in the center of the screen. ## Short answer Count words to compute vertical start row (25-n)/2, center each word horizontally at column (80-length)/2, print each word on its own line. Example good morning nepal prints three centered lines starting row 11. ## Answer **Assumptions:** 80 × 25 text screen. Each word is centred horizontally (column = (80 − length)/2) and the block of words is centred vertically (first row = (25 − number of words)/2). Words are separated by spaces. **Method:** `COUNT_WORDS` first counts the words to find the starting row. Then each word is located (skip spaces, find its length), the cursor is positioned with INT 10h function 02h, and the word is printed character by character. The row is incremented for the next word. ```asm .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: $' ROW DB 0 BUF DB 80, ?, 80 DUP(0) ; DOS buffered-input area (max, actual, chars) CRLF DB 13,10,'$' .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 CALL COUNT_WORDS ; AL = number of words MOV DH,0 CMP AL,25 JAE ROWSET ; too many words -> start at row 0 MOV DH,25 SUB DH,AL SHR DH,1 ; start row = (25 - n) / 2 ROWSET: MOV ROW,DH CLRSCR LEA SI,BUF+2 WLOOP: SKIP:MOV AL,[SI] CMP AL,' ' JNE CHK INC SI ; skip blanks JMP SKIP CHK:CMP AL,0DH JE FINISH ; end of string MOV DI,SI ; find the length of this word XOR CX,CX LEN:MOV AL,[DI] CMP AL,' ' JE GOT CMP AL,0DH JE GOT INC DI INC CX JMP LEN GOT:MOV DL,80 SUB DL,CL SHR DL,1 ; column = (80 - length) / 2 MOV DH,ROW MOV BH,0 MOV AH,02H ; position cursor INT 10H PR: MOV DL,[SI] ; print the word MOV AH,02H INT 21H INC SI LOOP PR INC ROW ; next word on next row JMP WLOOP FINISH: MOV AH,02H ; park cursor at bottom MOV BH,0 MOV DX,1800H INT 10H MOV AH,4CH ; return to DOS INT 21H MAIN ENDP ; ---- count words of the string in BUF; returns AL = number of words COUNT_WORDS PROC LEA SI,BUF+2 XOR BX,BX ; BL = count, BH = 'inside a word' flag CW1:MOV AL,[SI] CMP AL,0DH ; Enter marks the end of the string JE CWEND CMP AL,' ' JE CWSP CMP BH,0 JNE CWNXT ; already inside a word INC BL ; a new word starts here MOV BH,1 JMP CWNXT CWSP:MOV BH,0 CWNXT:INC SI JMP CW1 CWEND:MOV AL,BL RET COUNT_WORDS ENDP END MAIN ``` **Example:** `good morning nepal` → three lines `good`, `morning`, `nepal`, each centred, starting at row 11. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How is the column for centring a word calculated on an 80-column screen? A. 80 x length B. (80 - length) / 2 C. 80 / length D. (80 + length) / 2 Answer: B. Subtracting the word length from 80 and halving leaves equal margins on both sides. (Key point: Column formula) 2. How is the first row chosen so the block of words is vertically centred? A. Row 0 always B. (25 + words) / 2 C. (25 - number of words) / 2 D. 25 - number of words Answer: C. COUNT_WORDS gives n, and the start row is (25 - n)/2; for 3 words this is row 11. (Key point: Starting row) 3. Which call places the cursor before a word is printed? A. INT 21h function 09h B. INT 10h function 02h C. INT 10h function 06h D. INT 16h function 00h Answer: B. INT 10h function 02h sets the cursor row (DH) and column (DL). (Key point: Cursor positioning) 4. Why must COUNT_WORDS run before printing? A. To clear the screen B. To read the string C. To convert letters to upper case D. The number of words is needed to calculate the vertical starting row Answer: D. The vertical centre depends on how many lines the words will occupy. 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