Validating Credit Cards Credit card numbers are not randomly chosen. There are rules that
determine which credit card numbers are valid. This is a limited attempt to prevent fraud. If you
just make up some number, it is unlikely to be valid. You are going to write a program to
determine if a number is a valid credit card number. A credit card number must have between 13
and 16 digits. The first digit or two deter mines what type of card it is: Begins with Card Type
Visa MasterCard 37 American Express Discover For our purposes, a number that doesn\'t begin
with one of these sequences is not a valid credit card number. The algorithm for validating credit
cards is credited to Hans Luhn of IBM. To illustrate the algorithm, we will use the sample
number 4388576018402626. First, we see that this must be a Visa card, since it starts with 4. To
validate it 1. Double every second digit from right to left. If doubling of a digit results in a two-
digit number, add up the two digits to get a single-digit number. 2 2 4 2 2 4 2 38 1 2 12 2 3) 5 2 8
2 16 (1 6-7) 4 2 2. Now, add all the single digit numbers from the previous step. 4 4 8 2 3 1 7 8
37 3. Add all the digits in the odd places from right to left in the number. 6 6 0 8 0 7 8 3 38 4.
Add these two values together. 37 38 75
Solution
#include #include #include int main(void) { double cardnumber; printf(\"Give me a
number: \ \"); scanf(\"%lf\", &cardnumber); if(cardnumber < 1000000000000 ||
cardnumber > 10000000000000000) { printf(\"INVALID\ \"); return 0; }
if(cardnumber < 100000000000000 && cardnumber > 9999999999999) {
printf(\"INVALID\ \"); return 0; } char creditcard[17]; sprintf(creditcard, \"%f\",
cardnumber); char* ptr_cc; ptr_cc = strtok(creditcard,\".\"); int card_size = strlen(ptr_cc);
int sum = 0; for(int i = 1; i < card_size; i+=2) { int x = creditcard[card_size-1-i] -
\'0\'; int prod = 2 * x; if(prod>=10) { prod = prod%10 + prod/prod%10;
} sum += prod; } for(int i = 0; i < card_size; i+=2) { int x =
creditcard[card_size-1-i] - \'0\'; sum += x; } if(sum%10 != 0) {
printf(\"INVALID\ \"); return 0; } else if(creditcard[0] == \'4\') {
printf(\"VISA\ \"); return 0; } else if(creditcard[0] == \'3\' && (creditcard[1] == \'7\' ||
creditcard[1] ==\'4\')) { printf(\"AMEX\ \"); return 0; } else if(creditcard[0] ==
\'5\' && (creditcard[1] >=\'1\' && creditcard[1] <=\'5\')) { printf(\"MASTERCARD\ \");
return 0; } else { printf(\"INVALID\ \"); return 0; } }.
What questions are descriptive studies designed to answerSoluti.pdf
1. What questions are descriptive studies designed to answer?
Solution
Descriptive studies are designed to understand the characteristics of a phenomenon or a
population. In a descriptive study, information is collected with out changing the environment.
For example, What are the characteristics of population of US? To understand the characteristics
of the population, one can collect population date age group wise, occupation wise, gender
wise,etc.
