Assembly Language Tutorial

 
 
 

Instructions

Input - Output Instructions

Display a character Read a character and display it on new line Display string Read digit, compute and display sum w/o variable Read digit, display difference w/o variable Read digit, compute, display sum using variable Read digit, display difference using variable Convert lower case letter in to upper case Read character, display in new line - user prompt Read 1st, middle, last initial - down left margin Read one hex digit, display next line in decimal Display 10*10 solid box asterisk - INT 21H and 9H Read 3 char show in middle of 11*11 box, beep comp

Flow Control Instructions

Print ASCII characters Print counting from 0 to 9 Print upper case letters from A to Z Print lower case letters from a to z in reverse Read letter print if it is \'?\' - simulation of if Read char print smallest - simulation of if-else Positive, negative num- simulation of switch-case Print upper case char - simulation of if-else then Simulation of if-else then structure Print ASCII characters - for loop simulation Print upper case A to Z - while loop simulation Print upper case A to Z - Do while loop simulation Read letters display in next line in alpha order Display digit in next line if fail prompt message Read hex digit display on next line in decimal Display capital letter in string alphabetically Show longest sequence consecutive alphabetically

Logic - Shift - Rotate Instructions

Convert upper to lower case - OR logic instruction Convert lower to upper - AND logic instruction Display even or odd number - TEST instruction Multiply content of AL by 8 - SHL instruction Divide content of AL by 4 - SHR instruction Store binary- BX,count bit value 1 w/o changing BX Read binary num, reverse its bit pattern Read binary number store in BX and display Read char- show ASCII in binary- 1 bit in ASC code Read char print ASCII in HEX till- carriage return Read HEX number and print in binary next line Read binary number and print in HEX next line Read 2 binary number and print its sum in binary Read 2 unsigned HEX num and print their sum Read string of decimal digit print sum in HEX Read str of char ter by CR show reverse order Read character using procedure goto next line Binary form & reverse bit of num - procedures Product by ADD, SHIFT instruction - procedure Display text with letters in each word reversed Validate expression READ store bin num in AX, RANDOM, WRITE

Multiplication - Division Instructions

Print factorial in binary form - MUL instruction Print num decimal form - DIV, OUTDEC proc Print factorial in decimal form - MUL, DIV instru Print num next line - proc for DECIMAL i/o Proc INDEC and OUTDEC, handle BackSpace key Proc INDEC and OUTDEC - files - INCLUDE instru Print factorial in dec form - MUL, DIV instruction Proc INDEC, OUTDEC - Handle OverFlow Read time in seconds display time HH:MM:SS Express - quarter, dime, nickel, pennie Read fraction form M/N print N decimal place GCD of two integers M and N

Arrays - Addressing Modes

Sum of array - sum in AX - Register Indirect Mode Initialize array with 0 using DUP instruction Enter an array of size 10 and display it Declare, initialize, print 2D array of size 5x5 Enter 2D array of 5x5 in row major order, print Print 3rd R x 4th C using Register Indirect Mode Display reversing array contents using STACK Reverse content of array - Register Indirect Mode Sort array using Bubble Sort method Sort an array using Select Sort method Print 2D array of size 4x5 in row major order Print 2D array of size 4x5 in column major order 2D arr clear 3rd row 4th column - Based Index Mode Compute class average on each exam Print name each student, average of 4 exams Insert single characters into array - it is sorted

String Instructions

Copy string into another using MOVSB, REP Read string, stores in variable using STOSB Display string using instruction LODSB Store display str - proc READ_STR, DISP_STR Count no of vowels constants - SCASB, REPNE

General Programs

Get and display the current system time
 
 
 .MODEL SMALL
 .STACK 100H

 .DATA
   PROMPT_1  DB  \'Enter the time in seconds up to 65535 = $\'
   PROMPT_2  DB  0DH,0AH,\'The time in hh:mm:ss format is = $\'
   SEPARATOR DB  \' : $\'

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

     LEA DX, PROMPT_1             ; load and display the string PROMPT_1
     MOV AH, 9
     INT 21H

     CALL INDEC                   ; call the procedure INDEC

     PUSH AX                      ; puah AX onto the STACK

     LEA DX, PROMPT_2             ; load and display the string PROMPT_2
     MOV AH, 9
     INT 21H

     POP AX                       ; pop a value from STACK into AX

     XOR DX, DX                   ; clear DX
     MOV CX, 3600                 ; set CX=3600
     DIV CX                       ; set AX=DX:AX\\CX , DX=DX:AX%CX

     CMP AX, 10                   ; compare AX with 10
     JGE @HOURS                   ; jump to label @HOURS if AX>=10

     PUSH AX                      ; push AX onto the STACK

     MOV AX, 0                    ; set AX=0
     CALL OUTDEC                  ; call the procedure OUTDEC

     POP AX                       ; pop a value from STACK into AX

     @HOURS:                      ; jump label
     CALL OUTDEC                  ; call the procedure OUTDEC

     MOV AX, DX                   ; set AX=DX

     PUSH AX                      ; push AX onto the STACK

     LEA DX, SEPARATOR            ; load and display the string SEPARATOR
     MOV AH, 9
     INT 21H

     POP AX                       ; pop a value from STACK into AX
     XOR DX, DX                   ; clear DX

     MOV CX, 60                   ; set CX=60
     DIV CX                       ; set AX=DX:AX\\CX , DX=DX:AX%CX

     CMP AX, 10                   ; compare AX with 10
     JGE @MINUTES                 ; jump to label @MINUTES if AX>=10

     PUSH AX                      ; push AX onto the STACK

     MOV AX, 0                    ; set AX=0
     CALL OUTDEC                  ; call the procedure OUTDEC

     POP AX                       ; pop a value from STACK into AX

     @MINUTES:                    ; jump label
     CALL OUTDEC                  ; call the procedure OUTDEC

     MOV BX, DX                   ; set BX=DX

     LEA DX, SEPARATOR            ; load and display the string SEPARATOR
     MOV AH, 9
     INT 21H

     MOV AX, BX                   ; set AX=BX

     CMP AX, 10                   ; compare AX with 10 
     JGE @SECONDS                 ; jump to label @SECONDS if AX>=10

     PUSH AX                      ; push AX onto the STACK 

     MOV AX, 0                    ; set AX=0
     CALL OUTDEC                  ; call the procedure OUTDEC

     POP AX                       ; pop a value from STACK into AX

     @SECONDS:                    ; jump label
     CALL OUTDEC                  ; call the procedure OUTDEC

     MOV AH, 4CH                  ; return control to DOS
     INT 21H
   MAIN ENDP



 ;-------------------------  Procedure Definitions  ------------------------;




 ;-------------------------------  INDEC  ----------------------------------;


 INDEC PROC
   ; this procedure will read a number in decimal form    
   ; input : none
   ; output : store binary number in AX
   ; uses : MAIN

   PUSH BX                        ; push BX onto the STACK
   PUSH CX                        ; push CX onto the STACK
   PUSH DX                        ; push DX onto the STACK

   JMP @READ                      ; jump to label @READ

   @SKIP_BACKSPACE:               ; jump label
   MOV AH, 2                      ; set output function
   MOV DL, 20H                    ; set DL=\' \'
   INT 21H                        ; print a character

   @READ:                         ; jump label
   XOR BX, BX                     ; clear BX
   XOR CX, CX                     ; clear CX
   XOR DX, DX                     ; clear DX

   MOV AH, 1                      ; set input function
   INT 21H                        ; read a character

   CMP AL, \"-\"                    ; compare AL with \"-\"
   JE @MINUS                      ; jump to label @MINUS if AL=\"-\"

   CMP AL, \"+\"                    ; compare AL with \"+\"
   JE @PLUS                       ; jump to label @PLUS if AL=\"+\"

   JMP @SKIP_INPUT                ; jump to label @SKIP_INPUT

   @MINUS:                        ; jump label
   MOV CH, 1                      ; set CH=1
   INC CL                         ; set CL=CL+1
   JMP @INPUT                     ; jump to label @INPUT

   @PLUS:                         ; jump label
   MOV CH, 2                      ; set CH=2
   INC CL                         ; set CL=CL+1

   @INPUT:                        ; jump label
     MOV AH, 1                    ; set input function
     INT 21H                      ; read a character

     @SKIP_INPUT:                 ; jump label

     CMP AL, 0DH                  ; compare AL with CR
     JE @JUMP_TO_END_INPUT        ; jump to label @JUMP_TO_END_INPUT

     CMP AL, 8H                   ; compare AL with 8H
     JNE @NOT_BACKSPACE           ; jump to label @NOT_BACKSPACE if AL!=8

     CMP CH, 0                    ; compare CH with 0
     JNE @CHECK_REMOVE_MINUS      ; jump to label @CHECK_REMOVE_MINUS if CH!=0

     CMP CL, 0                    ; compare CL with 0
     JE @SKIP_BACKSPACE           ; jump to label @SKIP_BACKSPACE if CL=0
     JMP @MOVE_BACK               ; jump to label @MOVE_BACK

     @JUMP_TO_END_INPUT:          ; jump label

     JMP @END_INPUT               ; jump to label @END_INPUT

     @CHECK_REMOVE_MINUS:         ; jump label

     CMP CH, 1                    ; compare CH with 1
     JNE @CHECK_REMOVE_PLUS       ; jump to label @CHECK_REMOVE_PLUS if CH!=1

     CMP CL, 1                    ; compare CL with 1
     JE @REMOVE_PLUS_MINUS        ; jump to label @REMOVE_PLUS_MINUS if CL=1

     @CHECK_REMOVE_PLUS:          ; jump label

     CMP CL, 1                    ; compare CL with 1
     JE @REMOVE_PLUS_MINUS        ; jump to label @REMOVE_PLUS_MINUS if CL=1
     JMP @MOVE_BACK               ; jump to label @MOVE_BACK

     @REMOVE_PLUS_MINUS:          ; jump label
       MOV AH, 2                  ; set output function
       MOV DL, 20H                ; set DL=\' \'
       INT 21H                    ; print a character

       MOV DL, 8H                 ; set DL=8H
       INT 21H                    ; print a character

       JMP @READ                  ; jump to label @READ

     @MOVE_BACK:                  ; jump label

     MOV AX, BX                   ; set AX=BX
     MOV BX, 10                   ; set BX=10
     DIV BX                       ; set AX=AX/BX

     MOV BX, AX                   ; set BX=AX

     MOV AH, 2                    ; set output function
     MOV DL, 20H                  ; set DL=\' \'
     INT 21H                      ; print a character

     MOV DL, 8H                   ; set DL=8H
     INT 21H                      ; print a character

     XOR DX, DX                   ; clear DX
     DEC CL                       ; set CL=CL-1

     JMP @INPUT                   ; jump to label @INPUT

     @NOT_BACKSPACE:              ; jump label

     INC CL                       ; set CL=CL+1

     CMP AL, 30H                  ; compare AL with 0
     JL @ERROR                    ; jump to label @ERROR if AL<0

     CMP AL, 39H                  ; compare AL with 9
     JG @ERROR                    ; jump to label @ERROR if AL>9

     AND AX, 000FH                ; convert ascii to decimal code

     PUSH AX                      ; push AX onto the STACK

     MOV AX, 10                   ; set AX=10
     MUL BX                       ; set AX=AX*BX
     MOV BX, AX                   ; set BX=AX

     POP AX                       ; pop a value from STACK into AX

     ADD BX, AX                   ; set BX=AX+BX
     JC @ERROR

     CMP CL, 5
     JG @ERROR  
   JMP @INPUT                     ; jump to label @INPUT

   @ERROR:                        ; jump label

   MOV AH, 2                      ; set output function
   MOV DL, 7H                     ; set DL=7H
   INT 21H                        ; print a character

   XOR CH, CH                     ; clear CH

   @CLEAR:                        ; jump label
     MOV DL, 8H                   ; set DL=8H
     INT 21H                      ; print a character

     MOV DL, 20H                  ; set DL=\' \'
     INT 21H                      ; print a character

     MOV DL, 8H                   ; set DL=8H
     INT 21H                      ; print a character
   LOOP @CLEAR                    ; jump to label @CLEAR if CX!=0

   JMP @READ                      ; jump to label @READ

   @END_INPUT:                    ; jump label

   CMP CH, 1                      ; compare CH with 1   
   JNE @EXIT                      ; jump to label @EXIT if CH!=1
   NEG BX                         ; negate BX

   @EXIT:                         ; jump label

   MOV AX, BX                     ; set AX=BX

   POP DX                         ; pop a value from STACK into DX
   POP CX                         ; pop a value from STACK into CX
   POP BX                         ; pop a value from STACK into BX

   RET                            ; return control to the calling procedure
 INDEC ENDP


 ;--------------------------------  OUTDEC  --------------------------------;


 OUTDEC PROC
   ; this procedure will display a decimal number
   ; input : AX
   ; output : none
   ; uses : MAIN

   PUSH BX                        ; push BX onto the STACK
   PUSH CX                        ; push CX onto the STACK
   PUSH DX                        ; push DX onto the STACK

   CMP AX, 0                      ; compare AX with 0
   JGE @START                     ; jump to label @START if AX>=0

   PUSH AX                        ; push AX onto the STACK

   MOV AH, 2                      ; set output function
   MOV DL, \"-\"                    ; set DL=\'-\'
   INT 21H                        ; print the character

   POP AX                         ; pop a value from STACK into AX

   NEG AX                         ; take 2\'s complement of AX

   @START:                        ; jump label

   XOR CX, CX                     ; clear CX
   MOV BX, 10                     ; set BX=10

   @OUTPUT:                       ; loop label
     XOR DX, DX                   ; clear DX
     DIV BX                       ; divide AX by BX
     PUSH DX                      ; push DX onto the STACK
     INC CX                       ; increment CX
     OR AX, AX                    ; take OR of Ax with AX
   JNE @OUTPUT                    ; jump to label @OUTPUT if ZF=0

   MOV AH, 2                      ; set output function

   @DISPLAY:                      ; loop label
     POP DX                       ; pop a value from STACK to DX
     OR DL, 30H                   ; convert decimal to ascii code
     INT 21H                      ; print a character
   LOOP @DISPLAY                  ; jump to label @DISPLAY if CX!=0

   POP DX                         ; pop a value from STACK into DX
   POP CX                         ; pop a value from STACK into CX
   POP BX                         ; pop a value from STACK into BX

   RET                            ; return control to the calling procedure
 OUTDEC ENDP





 END MAIN

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