1. MSDOS 16-bit programming
chpt 13

2. helloworld TITLE Hello World Program (Hello.asm)
; This program displays "Hello, world!"
.model small
.stack 100h
.386
.data
message BYTE "Hello, world!",0dh,0ah
.code
main PROC
mov
mov ds,ax
mov ah,40h ; write to file/device
mov bx,1 ; output handle
mov cx,SIZEOF message ; number of bytes
mov dx,OFFSET message ; addr of buffer
int 21h
.exit
main ENDP
END main

3. hello.asm C:\MASM615\EXAMPLES\CH13>hello Hello, world!

4. Encrypt.asm: file encryption using XOR (char,value) and file redirect
This is the same idea we encountered in an earlier chapter, but it combines xor encryption with file redirection. To run you might type:
C:\MASM615\EXAMPLES\CH13>encrypt<secret.txt>message.txt

5. Encrypt.asm TITLE Encryption Program (Encrypt.asm)
;; read and encrypt a file. Run it from the
; command prompt, using redirection:
; Encrypt < infile.txt > outfile.txt
; Function 6 is also used for output, to avoid
; filtering ASCII control characters.
INCLUDE Irvine16.inc
XORVAL = 239 ; any value between 0-255
.code
main PROC
mov
mov ds,ax
L1: mov ah,6 ; direct console input
mov dl,0FFh ; don't wait for character
int 21h ; AL = character
jz L2 ; quit if ZF = 1 (EOF)
xor al,XORVAL
mov ah,6 ; write to output
mov dl,al
int 21h
jmp L1 ; repeat the loop
L2: exit
main ENDP
END main

6. uses dos redirection (< and >)
C:\MASM615\EXAMPLES\CH13>encrypt<secret.txt>message.txt
C:\MASM615\EXAMPLES\CH13>
secret.txt
secret message
contained here
message.txt:
œŠŒŠ›Ï‚ŠœœŽˆŠÏâ匀›Ž†Š‹Ï‡ŠŠ

7. Made some changes to this program
TITLE Buffered Keyboard Input (Keybd.asm)
; Test function 3Fh, read from file or device
; with the keyboard. Flush the buffer.
INCLUDE Irvine16.inc
.data
firstName BYTE 15 DUP(?)
terminal1 byte 0
lastName BYTE 30 DUP(?)
terminal2 byte 0
.code
main PROC
mov
mov ds,ax

8. Keybd continued ; Input the first name: mov ah,3Fh mov bx,0 ; keyboard
mov cx,LENGTHOF firstName
mov dx,OFFSET firstName
int 21h
; Disable the following line to see what happens
; when the buffer is not flushed:
call FlushBuffer
; Input the last name:
mov cx,LENGTHOF lastName
mov dx,OFFSET lastName
quit: call Crlf
mov dx,offset firstname
call writeString
call Crlf
mov dx,offset lastname

9. Flush type-ahead buffer to eoln;
FlushBuffer PROC ;
; Flush the standard input buffer.
; Receives: nothing. Returns: nothing ;
.data
oneByte BYTE ?
.code
pusha
L1:
mov ah,3Fh ; read file/device
mov bx,0 ; keyboard handle
mov cx,1 ; one byte
mov dx,OFFSET oneByte ; save it here
int 21h ; call MS-DOS
cmp oneByte,0Ah ; end of line yet?
jne L1 ; no: read another
popa
ret
FlushBuffer ENDP
END main

10. Run keybd C:\MASM615>keybd first has a max of 15 chars
last has a max of 30xxxxxxxxxxxxxxxxxxxxxxxx
first has a max
last has a max of 30xxxxxxxxxx

11. read from file or device
C:\MASM615\EXAMPLES\CH13>keybd
C:\MASM615\EXAMPLES\CH13>

12. DateTime.asm Include Irvine16.inc Write PROTO char:BYTE .data
str1 BYTE "Date: ",0
str2 BYTE ", Time: ",0
.code
main PROC
mov
mov ds,ax
; Display the date:
mov dx,OFFSET str1
call WriteString
mov ah,2Ah ; get system date
int 21h
movzx eax,dh ; month
call WriteDec
INVOKE Write,'-'
movzx eax,dl ; day
movzx eax,cx ; year
; Display the time:
mov dx,OFFSET str2
mov ah,2Ch ; get system time
movzx eax,ch ; hours
call WritePaddedDec
INVOKE Write,':'
movzx eax,cl ; minutes
movzx eax,dh ; seconds
call Crlf
exit
main ENDP

13. DateTime.asm ;---------------------------------------------
Write PROC char:BYTE
; Display a single character.
push eax
push edx
mov ah,2
mov dl,char
int 21h
pop edx
pop eax
ret
Write ENDP
WritePaddedDec PROC
; Display unsigned integer in EAX, padding
; to two digit positions with a leading zero.
.IF eax < 10
mov dl,'0'
.ENDIF
call WriteDec
WritePaddedDec ENDP
END main

14. DateTime.asm C:\MASM615\EXAMPLES\CH13>datetime

15. What is a binary file?
If you write chars (or – in java- strings) to a file, it contains numerical values 16 (or 32) bits per char depending if it is ASCII or Unicode.
If you write numbers to a file – say dword values- it contains 4 bytes per value.
This latter could be said to be a binary file.

16. binfile.asm TITLE Binary File Program (Binfile.asm)
; Create a binary file containing an array
; of doublewords.
; Last update: 11/12/01
INCLUDE Irvine16.inc
.data
myArray DWORD 50 DUP(?)
fileName BYTE "binary array file.bin",0
fileName2 BYTE "file2.bin",0
fileHandle WORD ?
commaStr BYTE ", ",0
; Set CreateFile to zero if you just want to
; read and display the existing binary file.
CreateFile = 1
.code
main PROC
mov
mov ds,ax
.IF CreateFile EQ 1
call FillTheArray
call DisplayTheArray
call CreateTheFile
call WaitMsg
call Crlf
.ENDIF
call ReadTheFile
quit:
exit
main ENDP

17. binfile.asm ;------------------------------------------------------
ReadTheFile PROC ;
; Open and read the binary file.
; Receives: nothing. Returns: nothing
mov ax,716Ch ; extended file open
mov bx,0 ; mode: read-only
mov cx, ; attribute: normal
mov dx,1 ; open existing file
mov si,OFFSET fileName ; filename
int 21h ; call MS-DOS
jc quit ; quit if error
mov fileHandle,ax ; save handle
; Read the input file, then close the file.
mov ah,3Fh ; read file
mov bx,fileHandle ; file handle
mov cx,SIZEOF myArray ; max bytes to read
mov dx,OFFSET myArray ; buffer pointer
int 21h
mov ah,3Eh ; function: close file
mov bx,fileHandle ; output file handle
int 21h ; call MS-DOS
quit:
ret
ReadTheFile ENDP

18. binfile.asm ;------------------------------------------------------
DisplayTheArray PROC ;
; Display the array
; Receives: nothing. Returns: nothing
mov CX,LENGTHOF myArray
mov si,0
L1:
mov eax,myArray[si] ; get a number
call WriteHex ; display the number
mov edx,OFFSET commaStr ; display a comma
call WriteString
add si,TYPE myArray ; next array position
loop L1
ret
DisplayTheArray ENDP
FillTheArray PROC
; Fill the array with random integers.
mov eax,1000h ; generate random integers
call RandomRange ; between in EAX
mov myArray[si],eax ; store in the array
FillTheArray ENDP

19. binfile.asm ;------------------------------------------------------
CreateTheFile PROC ;
; Create a file containing binary data
; Receives: nothing. Returns: nothing
mov ax,716Ch ; create file
mov bx,1 ; mode: write only
mov cx, ; normal file
mov dx,12h ; action: create/truncate
mov si,OFFSET fileName2 ; filename
int 21h ; call MS-DOS
jc quit ; quit if error
mov fileHandle,ax ; save handle
; Write integer array to the file.
mov ah,40h ; write file or device
mov bx,fileHandle ; output file handle
mov cx,SIZEOF myArray ; number of bytes
mov dx,OFFSET myArray ; buffer pointer
int 21h
; Close the file.
mov ah,3Eh ; function: close file
mov bx,fileHandle ; output file handle
int 21h ; call MS-DOS
quit:
ret
CreateTheFile ENDP
END main

20. binfile.asm C:\MASM615\EXAMPLES\CH13>binfile
000009E2, F6, 00000E87, , DF, 00000C10, A, 00000E78,
, , B4, , B4, 00000BB0, C9, 00000B59,
, E, 00000BCE, 00000CDB, DF, 00000C51, 00000E86, ,
000004F6, 00000E1C, 00000DF5, 00000C86, E, , F, 00000ED7,
000003DB, B, 00000D49, AA, B2, 00000B16, 00000B76, B4,
00000FE6, A, 00000AEA, 00000DE7, B, A, E9, 00000F79,
00000D36, BB, Press any key to continue...
00000D36, BB,
C:\MASM615\EXAMPLES\CH13>

21. fileio.asm TITLE Extended Open/Create (Fileio.asm)
; Demonstration of 16-bit FileIO under Windows 95/98/ME.
; The complete program does not appear in the text, but
; excerpts do appear.
; Last update: 11/12/01
INCLUDE Irvine16.inc
.data
Date WORD ?
handle WORD ?
actionTaken WORD ?
FileName BYTE "long_filename.txt",0
NewFile BYTE "newfile.txt",0
.code

22. fileio.asm main PROC mov ax,@data mov ds,ax
;Create new file, fail if it already exists:
mov ax,716Ch ; Extended Open/Create
mov bx,2 ; read-write
mov cx, ; normal attribute
mov dx,10h ; action: create
mov si,OFFSET NewFile
int 21h
jc failed
mov handle,ax ; file handle
mov actionTaken,cx ; action taken to open file
mov ax,cx
call writeint
call crlf
;Open existing file
mov bx,0 ; read-only
mov dx,1 ; open existing file
mov si,OFFSET Filename

23. fileio.asm ;Create new file or truncate existing file:
mov ax,716Ch ; Extended Open/Create
mov bx,2 ; read-write
mov cx, ; normal attribute
mov dx,10h + 02h ; action: create + truncate
mov si,OFFSET NewFile
int 21h
jc failed
mov handle,ax ; file handle
mov actionTaken,cx ; action taken to open file
mov ax,cx
call writeint
call crlf
failed:
exit
main ENDP
END main

24. fileio.asm
C:\MASM615\EXAMPLES\CH13>fileio +2 +1 +3

25. readfile TITLE Read a text file (Readfile.asm)
; Read, display, and copy a text file.
; Last update: 9/11/01
INCLUDE Irvine16.inc
.data
BufSize = 5000
infile BYTE "my_text_file.txt",0
outfile BYTE "my_output_file.txt",0
inHandle WORD ?
outHandle WORD ?
buffer BYTE BufSize DUP(?)
bytesRead WORD ?
.code
main PROC
mov
mov ds,ax

26. readfile ; Open the input file mov ax,716Ch ; extended create or open
mov bx, ; mode = read-only
mov cx,0 ; normal attribute
mov dx,1 ; action: open
mov si,OFFSET infile
int 21h ; call MS-DOS
jc quit ; quit if error
mov inHandle,ax
; Read the input file
mov ah,3Fh ; read file or device
mov bx,inHandle ; file handle
mov cx,BufSize ; max bytes to read
mov dx,OFFSET buffer ; buffer pointer
int 21h
mov bytesRead,ax
; Display the buffer
mov ah,40h ; write file or device
mov bx,1 ; console output handle
mov cx,bytesRead ; number of bytes
; Close the file
mov ah,3Eh ; function: close file
mov bx,inHandle ; input file handle
int 21h ; call MS-DOS

27. readfile ; Create the output file
mov ax,716Ch ; extended create or open
mov bx, ; mode = write-only
mov cx,0 ; normal attribute
mov dx,12h ; action: create/truncate
mov si,OFFSET outfile
int 21h ; call MS-DOS
jc quit ; quit if error
mov outHandle,ax ; save handle
; Write buffer to new file
mov ah,40h ; write file or device
mov bx,outHandle ; output file handle
mov cx,bytesRead ; number of bytes
mov dx,OFFSET buffer ; buffer pointer
int 21h
; Close the file
mov ah,3Eh ; function: close file
mov bx,outHandle ; output file handle
int 21h ; call MS-DOS
quit:
call Crlf
exit
main ENDP
END main

28. Run of readfile C:\MASM615>readfile here is a sample data file
with several
lines in it
1222
4445

29. Findfirst…findnext: dir

30. Findfirst…findnext: dir
.data
filename byte '*.asm',0
DTA label byte
search byte 21 dup(?)
other byte 9 dup(?)
fname byte 'namehereXXXX',0
.code
main PROC
mov
mov ds,ax ; must point ds to main
mov es,ax
mov dx, offset DTA
mov ah, 1Ah
int 21h ;;;set DTA to my buffer area
mov cx, 1 ;;; file attribute read-only
mov dx,offset filename
mov ah, 4Eh
int 21h
xor cx,cx
top: mov dx,offset fname
inc cx
test cx,3h
jnz writeit
call crlf
writeit: call writestring
blanks 5
mov ah,4fh
jnc top
quit: exit

31. Tabbing for the dir command: two macros
blanks macro count
local top
push cx
push ax
push dx
mov cx, count
mov dl,' '
mov ah, 2
top: int 21h
loop top
pop dx
pop ax
pop cx
endm
mygotoxy macro row, col
push bx
mov dh,row
mov dl,col
mov bh,0
mov ah,2
int 10h
pop bx

32. Tabbing for the dir command

33. Tabbing data area: I made up some strings
INCLUDE Irvine16.inc
.data
row byte 0
col byte 0
s1 byte 'some string',0
s2 byte 'and another',0
s3 byte 'shorty',0
s4 byte 'xyz',0
s5 byte 'bleh blah',0
addresses label word
word s1
entry=($-addresses)
word s2
word s3
word s4
word s5
numentries=($-addresses)/entry

34. tabbing call clrscr mov row,0 mov col,0 mov bx, 0
nextword: mygotoxy row,col ;start in upper lh corner
mov dx,addresses[bx]
mov di,dx
call writestring
add col, 20
add bx,2
cmp bx,numentries*2
jb checkrow
xor bx,bx
checkrow: cmp col,65
jb nextword
inc row
cmp row,24
quit: exit
main ENDP