$ unzip.exe libcs50-11.0.2.zip >/dev/null 2>&1
$ cd libcs50-11.0.2
$ make
make: Nothing to be done for 'all'.
$ /usr/bin/cp -i "Makefile" "Makefile.Original"
$# I modified Makefile related to CYGWIN
$ diff Makefile Makefile.Original
17c17
< OS := $(shell /usr/bin/uname | /usr/bin/sed "s/-[0-9]*\.[0-9]-[0-9]*//;")
---
> OS := $(shell uname)
19,24d18
< # CYGWIN_NT
< ifeq ($(OS),CYGWIN_NT)
<       LIB_BASE := $(BASENAME).so
<       LIB_MAJOR := $(BASENAME).so.$(MAJOR_VERSION)
<       LIB_VERSION := $(BASENAME).so.$(VERSION)
<       LINKER_FLAGS := -Wl,-soname,$(LIB_MAJOR)
26c20
< else ifeq ($(OS),Linux)
---
> ifeq ($(OS),Linux)
$ make
#...
install -m 644 src/cs50.h build/include
mv libcs50.so.11.0.2 libcs50.so libcs50.a build/lib
$ /usr/bin/find ./ -type f -name cs50.h
$ mv ./build/include/cs50.h /usr/include/
$ find ./ -type f -name "*.a" -exec grep -l get_long {} \;
./build/lib/libcs50.a
$ find ./ -type f -name "*.so*" -exec grep -l get_long {} \;
./build/lib/libcs50.so.11.0.2
$ mv ./build/lib/libcs50.so.11.0.2 ./build/lib/libcs50.a /usr/lib
$ /usr/bin/gcc.exe -I. -g -Wall 4175719828.c -o ./a.out -lcs50

#include <cs50.h>
#include <math.h>
#include <stdio.h>
int main(void)
{
        // Always initialize the variable
        long DebitCreditCardNum = 0;
        int sumOfProductDigits = 0;
        int sumOfNonProductDigits = 0; // sum of digits that are not products
        int checkSum = 0;
        long NumModulusTen = 0;
        long SecondModulusTen = 0;
        // Prompt user for credit card input.
        do
        {
                DebitCreditCardNum = get_long( "Number: " );
                // printf( "%li\n", DebitCreditCardNum);
        }
        while( 0 > DebitCreditCardNum );
        sumOfProductDigits = 0;
        sumOfNonProductDigits = 0;
        long ccNumbers1 = DebitCreditCardNum; // Used for checkSum
        long ccNumbers2 = DebitCreditCardNum; // Used for card validation
        while( 0 < ccNumbers1 )
        {
                NumModulusTen = ccNumbers1 % 10; // out: 4
                sumOfNonProductDigits += NumModulusTen; // add 4
                // printf( "Adding %li\n to sumOfNonProductDigits\n", NumModulusTen);
                ccNumbers1 = ccNumbers1 - NumModulusTen; // minus the last digit
                ccNumbers1 = ccNumbers1 / 10; // reduce by one last digit by dividing by 10
                // printf( "Updated ccNumbers1 after is: %li\n", ccNumbers1);
                // printf( "###########################\n" );
                // Second Number to iterate thru
                SecondModulusTen = ccNumbers1 % 10; // out: 1
                // printf( "Here's SecondModulusTen: %li\n \n", SecondModulusTen);
                // printf( "Sum Of Product Digits: %i\n \n", sumOfProductDigits);
                // printf( "Sum Of Non-Product Digits: %i\n \n", sumOfNonProductDigits);
                ccNumbers1 = ccNumbers1 - SecondModulusTen;
                ccNumbers1 /= 10;
                if( 9 < SecondModulusTen * 2 ) // if there's two digits you'll have to add each digit
                {
                        // Product result is double digits. Repeat the same thing to split numbers
                        // and reduce the ccNumbers1
                        SecondModulusTen = SecondModulusTen * 2;
                        int numSlice = SecondModulusTen % 10; // split by getting the last digit
                        sumOfProductDigits += numSlice;
                        sumOfProductDigits += ((SecondModulusTen - numSlice) / 10); // add to products sum
                }
                else
                {
                        // multiply the digit by 2 and add to sumOfProductDigits
                        SecondModulusTen = SecondModulusTen * 2;
                        sumOfProductDigits += SecondModulusTen;
                }
        }
        checkSum = sumOfProductDigits + sumOfNonProductDigits;
        // printf( "CHECK SUM: %i\n", checkSum);
        // Algorithm to check if card is valid:
        if( 0 == checkSum % 10 )
        {
                bool amex = false;
                bool mastercard = false;
                bool visa = false;
                amex =
                        (ccNumbers2 >= 340000000000000 && ccNumbers2 < 350000000000000) ||
                        (ccNumbers2 >= 370000000000000 && ccNumbers2 < 380000000000000);
                mastercard =
                        (ccNumbers2 >= 5100000000000000 && ccNumbers2 < 5600000000000000);
                visa =
                        (ccNumbers2 >= 4000000000000 && ccNumbers2 < 5000000000000) ||
                        (ccNumbers2 >= 4000000000000000 && ccNumbers2 < 5000000000000000);
                if(amex)
                {
                        printf( "AMEX\n" );
                }
                else if(mastercard)
                {
                        printf( "MASTERCARD\n" );
                }
                else if(visa)
                {
                        printf( "VISA\n" );
                }
                else
                {
                        printf( "%lu INVALID_NUMBER\n", DebitCreditCardNum );
                }
        }
        else
        {
                printf( "%lu INVALID NUMBER\n", DebitCreditCardNum );
        }
        return 0;
}
/*
01. Always initialize variables
02. Alwayse beter to write return/return0 based on the functions.
03. Replace:
        while (DebitCreditCardNum < 0);
        ...
        if
        ...
        else if
        ...
        for
With:
        while( 0 > DebitCreditCardNum );
        ...
        if
        ...
        else if
        ...
        for
Reason: new programmers may assign using:
        while( DebitCreditCardNum = 0 );
I have taken following ATM card numbers from internet images:
$ ./a.out
Number: 5333619503715702
MASTERCARD
$ a.out
Number: 5555555555554444
MASTERCARD
$ a.out
Number: 5454545454545454
MASTERCARD
$ a.out
Number: 4444333322221111
VISA
*/