Directory Listing Program

Let's write a short program that clears, displays the current disk directory, and asks
The user to enter a filename. (You might want to extend the "so it opens and displays the
Selected file.)
C + + Stub module the C + + module contains only a call to Asm_main, so we can call it a
Stub module:

// main.cpp // stub module:launches assembly language Program extern " C " void // asm startup proc void Main () {Asm_main ();}

ASM Module The assembly language module contains the function prototypes, several strings,
and a fileName variable. It calls the system function twice, passing it "CLS" and "dir" commands.

Then printf was called, displaying a prompt for a filename, and scanf are called so the user can input
The name. It does no calls to the IRVINE32 library, so we can set the. MODEL directive to
The C Language convention:

;ASM Program launched from C + + (ASMMAIN.ASM).586. MODEL Flat,c;Standard C library functions:System PROTO,Pcommand:PTR byteprintf PROTO,pstring:PTR BYTE,args:varargscanf PROTO,Pformat:PTR BYTE,pbuffer:PTR BYTE,args:Varargfopen PROTO,mode:PTR BYTE,FileName:PTR bytefclose PROTO,PFile:dwordbuffer_size = the. DATASTR1 BYTE"CLS",0str2 BYTE"dir/w",0STR3 BYTE"Enter The name of a file:",0STR4 BYTE"%s",0STR5 BYTE"cannot open file", 0dh,0ah,0STR6 BYTE"The file has been opened", 0dh,0ah,0modestr BYTE"R",0fileName BYTE -DUP (0) PBuf DWORD? pFile DWORD?. Codeasm_main PROC;Clear the screen, display disk directoryINVOKE system,addr str1invoke system,addr str2;ask for a filenameINVOKE printf,addr str3invoke scanf, ADDR str4, ADDR filename;try to open the fileINVOKE fopen, ADDR fileName, ADDR modestrmovPfile,eax. IF EAX = =0 ;cannot open file?INVOKE printf,addr STR5jmpquit. Elseinvoke printf,addr STR6. ENDIF;Close the fileINVOKE fclose, PFilequit:ret ;return to C + + mainAsm_main endpend

The scanf function requires the arguments:the first is a pointer to a format string ("%s"), and
The second is a pointer to the input string variable (fileName). We won't take the time to
Explain standard C functions because there are ample documentation on the WEB. An excellent
Reference is Brian W. Kernighan and Dennis M. Ritchie, the C programming Language, 2nd
Ed., Prentice Hall, 1988.

Directory Listing Program