Q. Program for encoding ASCII Alpha numeric?

; A program for encoding ASCII Alpha numeric.

; ALGORITHM:

            ; create the code table

            ; read an input string character by character

            ; translate it using code table 

            ; output the strings 

 DATA   SEGMENT

CODETABLE DB 48 DUP (0); no translation of first 

                                                ; 48 ASCII

                                    DB '4590821367'; ASCII codes 48 - 

                                                ; 57 ≡ (30h - 39h)

                                        DB 7 DUP (0); no translation of          these 7 characters

                                        DB    'GVHZUSOBMIKPJCADLFTYEQNWXR'

                                        DB 6 DUP (0); no translation

                                        DB  'gvhzusobmikpjcadlftyeqnwxr'

                                        DB 133 DUP (0); no translation of remaining 

                                                 ; Character

DATA ENDS

CODE SEGMENT

            MOV AX, DATA

            MOV DS, AX   ; initialize DS

            MOV BX, OFFSET CODETABLE; point to lookup table

GETCHAR:     

            MOV AH, 06; console input no wait

            MOV DL, 0FFh   ; specify input request

            INT 21h; call DOS

            JZ QUIT   ; quit if no input is waiting

            MOV DL, AL   ; save character in DL

            XLAT CODETABLE; translate the character

            CMP AL, 0; translatable?

            JE PUTCHAR   ; no: write it as is.

            MOV DL, AL; yes: move new character

                                    ; To DL

PUTCHAR:     

   MOV AH, 02   ; write DL to output 

   INT 21h  

   JMP   GETCHAR; get another character

QUIT:             MOV AX, 4C00h  

   INT 21h  

CODE ENDS    

END

Discussion: 

The program above will code the data. For illustration a line from an input file will be encoded:

A SECRET Message                          (Read from an input file)

G TUHFUY Juttgou                           (Encoded output)

The program above can be run by using following command line. If program file name is coding.asm

Coding infile > outfile 

The infile is input data file and outfile is output data file.

You can write more such applications by using 8086 assembly tables.