Assembly Language Tutorial



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 Read hex digit display on next line in decimal Display digit in next line if fail prompt message 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
 .STACK 100H

   PROMPT_1  DB  \'Enter a Binary number (max 16-bit) : $\'
   PROMPT_2  DB  0DH,0AH,\'The equivalent Decimal number is : $\'
   ILLEGAL   DB  0DH,0AH,\'Illegal character. Try again : $\'

     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 BINARY_INPUT            ; call the procedure BINARY_INPUT

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

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

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

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

 ;----------------------------  BINARY_INPUT  ------------------------------;

   ; this procedure will read a number in binary form    
   ; input : none
   ; output : store binary number in BX
   ; uses : MAIN

   JMP @AGAIN                     ; jump to label @AGAIN 

   @ERROR:                        ; jump label

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

   @AGAIN:                        ; jump label

   MOV CX, 16                     ; initialize loop counter
   XOR BX, BX                     ; clear BX
   MOV AH, 1                      ; set input function

   @INPUT:                        ; loop label
     INT 21H                      ; read a digit

     CMP AL, 0DH                  ; compare input and CR
     JE @END                      ; jump to label @END if input is CR

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

     CMP AL, 31H                  ; compare AL with 1
     JG @ERROR                    ; jump to label @ERROR if AL>1

     AND AL, 0FH                  ; convert ascii to decimal code
     SHL BX, 1                    ; shift BX by 1 position towards left
     OR  BL, AL                   ; place the input decimal digit in BL
   LOOP @INPUT                    ; jump to label @INPUT if CX!=0

   @END:                          ; jump label

   RET                            ; return control to the calling procedure

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

   ; 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

   @REPEAT:                       ; 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 @REPEAT                    ; jump to label @REPEAT 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


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