The code adds a comment into old DOS created zip-archive.

zipcomm.asm

ASSUME    CS:CGR,DS:CGR
CGR	GROUP	COD,DAT
COD	SEGMENT BYTE
ORG	100H
ZIPCOMM proc
	LEA	SI,C_
	CALL	WW
	MOV	SI,80H
	MOV	AH,'/'
	CALL	READ_FILE_STRING
	JC	RFSE
	LODSB
	CMP	CX,2
	JNE	FQE
	PUSH	SI
	XCHG	SI,DX
	MOV	AX,3D01H
	INT	21H
	JC	FE
	MOV	BX,AX
	MOV	AX,4202H
	XOR	CX,CX
	DEC	CX
	MOV	DX,CX
	DEC	DX
	INT	21H
	JC	FE
	POP	SI
	PUSH	BX
	CALL	NEXT_FILE
	LEA	DX,BUF_
	PUSH	DX;?
	XOR	AX,AX
	DEC	AX
	CALL	LOAD_FILE
	JC	FE
	MOV	DS:[LEN_COMM_],CX
	POP	DX;?
	POP	BX
	ADD	CX,2
	SUB	DX,2
	CALL	WRITE_FILE
	JC	FE
	MOV	AH,3EH
	INT	21H
	JC	FE
	LEA	SI,OK
E1:
	CALL	WW
E:
	MOV	AX,4C00H
	INT	21H
RFSE:
	LEA	SI,H
	JMP	SHORT	E1
FQE:
	CMP	CX,2
	JB	FQE1
	LEA	SI,FQEMAX
	JMP	SHORT	E1
FQE1:
	LEA	SI,FQEMIN
	CALL	WW
	LEA	SI,H
	JMP	SHORT	E1
FE:
	CALL	PRINT_IO_ERRORS
	JMP	SHORT	E
NEXT_FILE	PROC
	LODSB
	OR	AL,AL
	JNZ	NEXT_FILE
	RET
ENDP
INCLUDE ..\..\LIBRARY\FILE\READFSTR.LIB
INCLUDE ..\..\LIBRARY\FILE\IO.LIB
INCLUDE ..\..\LIBRARY\TEXT\WW.LIB
INCLUDE ..\..\LIBRARY\FILE\IOERRORS.LIB
endp
ENDS
DAT	SEGMENT BYTE
C_	DB	'Zip comment creater 1.0 betta by Pavel Skrylev',0DH,0AH,0
FQEMAX	DB	'Very many files',0DH,0AH,0
FQEMIN	DB	'Need two files',0DH,0AH,0
H	DB	'   USAGE: zipcomm.com <zipfile> <commentfile>',0DH,0AH,0
OK	DB	'Archiv updated',0DH,0AH,0
LEN_COMM_	DW	0
BUF_:
ENDS
END  ZIPCOMM