asked on

Testing Credit Card Number

I want to make a procedure for testing a Credit Card number (VISA card), but I don't knew how to do this. Can
you help me, please?

ecw

I used to do this sort of stuff many years ago when I was an EPOS programmer. It's a very simple checkdigit algorithm which I have forgotten - there isn't much call for it day to day. However a quick search on Alta Vista found this:

URL: http://www.plato-net.or.jp/usr/vladimir/ugtxt/txt/creditalgorith.html

This algorithm is used for credit and charge cards. Store loyalty cards often depend on obscene account number length eg. 24+ digits.

Here is a simple bit of code to check a card number based on the content of the above page. It returns non-zero if the card no. is ok, and puts the calculated check digit in *check_digit.

Ed.

--CUT HERE--
#include <string.h>

int check_card(char *card, int *check_digit)
{
char *c;
char *last = card + strlen(card + 1);
int dval;
int cval;
int cpos;

for (c = card, cpos = 1, cval = 0; c < last; ++c, ++cpos) {
if ((dval = (*c - '0') * (1 + (cpos & 1))) > 9) {
dval = dval - 9;
}
cval += dval;
}
return (*check_digit = 10 - (cval % 10)) == (*last - '0');
}

int main(argc, argv)
int argc;
char *argv[];
{
int cd;
while (--argc) {
++argv;
if (check_card(*argv, &cd)) {
printf("Check succeeded (%s)\n", *argv);
} else {
printf("Check failed (%s) - should be %-d\n", *argv,cd);
}
}
return 0;
}

ecw

Bugger, this is the pascal group, and I've just chucked in some 'C'. Believe it or not, most of the EPOS work (I alluded to above) was in Pascal, so here goes...
Description is basically same as 'C' version, but it needs extra parameter clen - the length of the card number.
Ed.

function check_card(card : packed array [1..32] of char; clen : integer; var cd : integer) : boolean
var
c : integer;
cpos : integer;
dval : integer;
cval : integer;
begin
cpos := 1; dval := 0; cval := 0;
while (cpos < clen)
begin
dval := ord(card[cpos]) * (1 + (cpos mod 2));
if (dval > 9) dval := dval - 9;
cval := cval + dval;
end;
cd := 10 - (cval mod 10);
check_card := cd = ord(card[clen])
end;

ecw

Again, my pascal is very rusty. So here's something that compiles at least.

function check_card(card : array of char; clen : integer; var cd : integer) : boolean;
var
c : integer;
cpos : integer;
dval : integer;
cval : integer;
begin
cpos := 1; dval := 0; cval := 0;
while (cpos < clen) do
begin
dval := ord(card[cpos]) * (1 + (cpos mod 2));
if (dval > 9) then dval := dval - 9;
cval := cval + dval;
end;
cd := 10 - (cval mod 10);
check_card := cd = ord(card[clen])
end;

omsec

hm, i didnt test it, but i think you can't give an ARRAY as Argument to a Function. Try to create first a TYPE and then give a such VAR to the Function. Maybe this helps...

TYPE
CardData : Array [0..32] of Char (would be String[32] anyway)

VAR
Card : CardData;

perhaps you used null-terminated strings from C, what in Pascal would be pChar.

ASKER CERTIFIED SOLUTION

mmilan

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ozo

For MasterCard, the first digit should be 5
For Visa, it should be 4,
For Discover card, 6
For American Express, the first two digits, should be 3 7

keksperte

And this is from me and from the book VBScript4dummies.
It's html but it works and the code is easy enough to convert to pascal, or isn't it?

//--------------- Code starts -------------------------------------------------------------------
Sub CheckCard_OnClick()
Select case CardType(CardNum.Value)
Case "BLANK"
Msg = "Diese Zahl ist keine Kreditkartennummer"
Icon=16
Case "NONNUMBER"
Msg = "Diese Zahl enthält mindestens ein nicht-numerisches Zeichen"
Icon=16
Case "AMEX"
Msg ="Dies ist eine gültige American Express-Kartennummer"
Icon=64
Case "VISA"
Msg ="Dies ist eine gültige Visa-Kartennummer"
Icon=64
Case "MASTER"
Msg ="Dies ist eine gültige MasterCard-Kartennummer"
Icon=64
Case "DISCOVER"
Msg = "Dies ist eine gültige Discover-Kartennummer"
Icon=64
Case "INVALID"
Msg = "Diese Kreditkartennummer ist UNGÜLTIG"
Icon=16
End Select
Msg = CardNum.Value & chr(13) & chr(13) & Msg
Msgbox Msg, Icon, "Überprüfung der Kreditkartennummer"
End Sub

''''''''''''''''''
Sub ClearFields_OnClick()
CardNum.Value=""
End Sub

''''''''''''''''
Function CardType(N)
Dim i, CheckSum, Prod
MASK = "2121212121212121"
Num=N

if Num="" then
CardType="LEER"
exit function
end if

' Remove spaces
NumDigits=Len(Num)
TempNum=""
for i=1 to NumDigits
Digit=mid(Num,i,1)
if Digit <> " " Then TempNum=TempNum & Digit
next

' Remove dashes
TempNum2=""
for i=1 to Len(TempNum)
Digit=mid(TempNum,i,1)
if Digit <> "-" Then TempNum2=TempNum2 & Digit
next

' Check for non-numbers
for i=1 to len(TempNum2)
if not isnumeric(mid(TempNum2,i,1)) then
CardType="BLANK"
exit function
end if
next
Num=TempNum2

' Determine card type
If Left(Num, 2) = "37" Then CardType = "AMEX"
If Left(Num, 1) = "4" Then CardType = "VISA"
If Left(Num, 1) = "5" Then CardType = "MASTER"
If Left(Num, 1) = "6" Then CardType = "DISCOVER"

' Make card length = 16
Select Case Len(Num)
Case 13: Num = "000" & Num
Case 14: Num = "00" & Num
Case 15: Num = "0" & Num
Case 16: Num = Num
Case Else
CardType="UNGÜLTIG"
Exit Function
End Select

' Calculate check sum
CheckSum = 0
For i = 1 To 16
Prod = Mid(Num, i, 1) * Mid(MASK, i, 1)
If Prod > 9 Then Prod = Prod - 9
CheckSum = CheckSum + Prod
Next
CheckSum = CheckSum Mod 10

' Invalid card
If CheckSum <> 0 Then
CardType="UNGÜLTIG"
Exit Function
End If
End Function

//------------------- Code ends -----------------------------------------------------------

;-)

ozo

That might be ok if you don't accept Diner's Club, which would start with 3, and have a second digit other than 7...

waleed072098

jjkhkjhjhj

milance

ASKER

How can I test expiriens date?

alexo

You cannot