Diversifying Ruined

As part of work requirement, my colleague sent me a program called "NRIC Checker". Basically, its a program that returns you the last alphabet of a particular NRIC given the first seven digits. I remembered I came across the computation of the last alphabet few years ago. Out of curiousity, I googled for the formula.

The Singapore NRIC Check Digit

The Singapore NRIC number is made up of 7 digits and a letter behind. This letter is calculated from the first 7 digits using the modulus eleven method.

The steps involved to obtain the check digit is

1. Multiply each digit in the NRIC number by its weight.
2. Add together the above products.
3. Divide the resulting sum by 11.
4. Subtract the remainder from 11 to give the check digit.
5. Check the check digit against the table to obtain the alphabet.

The following table shows the weight for the NRIC number in Singapore :

2

7

6

5

4

3

2

The following table is used to change the check digit into the corresponding alphabet.

Check Digit	1	2	3	4	5	6	7	8	9	10	11
Alphabet	A	B	C	D	E	F	G	H	I	Z	J

This system is used to prevent illegal workers from entering Singapore with a fake passport using a fake NRIC number.

e.g A person has a NRIC number S1234567A.

To find out if the NRIC number is valid, we need to use the method above.

2(weight)*1(NRIC number) + 7(weight)*2(NRIC number) + 6*3 + 5*4 + 4*5 + 3*6 + 2*7 = 106

106/11 = 9 r 7

11-7 = 4

Using the table above, if the check digit is 4, then the alphabet at the end of the NRIC number should be D. So, we can conclude that this NRIC number is invalid.

Source.