UP student number checksum - Revision history

137.215.117.75: /* Student assistants */

2013-01-29T11:20:48Z

‎Student assistants

Alchemyst: Student assistent codes described.

2012-04-25T10:04:36Z

Student assistent codes described.

137.215.117.105: /* Code */

2010-09-21T11:18:21Z

‎Code

Alchemyst: /* Basic */

2010-03-11T08:29:29Z

‎Basic

Alchemyst: Created page with '== UP student number checksum == The last digit of UP student numbers is a check digit, calculated according to the similar rules as an [http://en.wikipedia.org/wiki/Check_digit#...'

2010-03-11T08:27:02Z

Created page with '== UP student number checksum == The last digit of UP student numbers is a check digit, calculated according to the similar rules as an [http://en.wikipedia.org/wiki/Check_digit#...'

New page

== UP student number checksum ==
The last digit of UP student numbers is a check digit, calculated according to the similar rules as an [http://en.wikipedia.org/wiki/Check_digit#ISBN_10 ISBN 10]. ISBN 10 check digit is calculated "so that multiplying each digit by its position in the number (counting from the right) and taking the sum of these products modulo 11 is 0" (from Wikipedia). It appears as though the UP check digit does not have a similarly easy check for validity, although the calculation of the check digit is similar up to a point.

=== The sum ===
To calculate the check digit for a 7 digit student number, follow this procedure. Take the first digit and multiply by 8, the second by 7, the third by 6 and so on:

{|
|Digit || 9 || 7 || 0 || 0 || 8 || 0 || 4
|-
|i || 8 || 7 || 6 || 5 || 4 || 3 || 2
|-
|Product || 72 || 49 || 0 || 0 || 32 || 0 || 8
|}

Add the products together and call this <math>s</math>. In the example above, <math>s=161</math> The check digit is now <math>(12 - s \mod 11) \mod 10</math>. For the example, we would get <math>(12 - 161 \mod 11) \mod 10 = (12 - 7) \mod 10 = 5</math>.

=== Code ===

==== Awk ====
This awk program recognises short student numbers at the beginnig of lines and replaces the first field with the long student number
<pre>
/^s[0-9][0-9][0-9][0-9][0-9][0-9][0-9]/ {
split($1, digits, "");
s = 0
for (i=2; i<9; i++)
s += digits[i] * (10-i);
$1 = $1 (12 - (s % 11)) % 10
}
{print}
</pre>

==== Python ====
This python function calculates the check digit of a short student number passed as a string:

<pre>
def checkdigit(short):
# Calculate check digit
s = sum(int(char)*(8-i) for i,char in enumerate(short))
return (12 - (s % 11)) % 10
</pre>

==== Basic ====
This Basic program (suitable for calls from MS Excel or OpenOffice Calc, calculates the check digit:

<pre>
function checkdigit(numstr as variant) as integer
' calculates the check digit (8th number) of a 7 digit student number
dim i, s as integer

s = 0
for i = 1 to 7
s = s + CInt(mid(numstr, i, 1))*(9-i)
next i

checkdigit = (12 - (s mod 11)) mod 10
end function
</pre>

@@ Line 16: / Line 16: @@
 === Student assistants ===
-It appears that "student numbers" for student assistents which start with "04" rather than a number representing the year have a minor alteration to the checksum code - the code calculated above is 1 too large.  It is not certain at this point if the same calculation is carried out and 1 subtracted or if the code is calculated with a different modulus.
+It appears that "student numbers" for student assistants which start with "04" rather than a number representing the year have a minor alteration to the checksum code - the code calculated above is 1 too large.  It is not certain at this point if the same calculation is carried out and 1 subtracted or if the code is calculated with a different modulus.
 === Code ===

← Older revision		Revision as of 10:04, 25 April 2012
Line 14:		Line 14:

	Add the products together and call this <math>s</math>. In the example above, <math>s=161</math> The check digit is now <math>(12 - s \mod 11) \mod 10</math>. For the example, we would get <math>(12 - 161 \mod 11) \mod 10 = (12 - 7) \mod 10 = 5</math>.		Add the products together and call this <math>s</math>. In the example above, <math>s=161</math> The check digit is now <math>(12 - s \mod 11) \mod 10</math>. For the example, we would get <math>(12 - 161 \mod 11) \mod 10 = (12 - 7) \mod 10 = 5</math>.
		+
		+	=== Student assistants ===
		+	It appears that "student numbers" for student assistents which start with "04" rather than a number representing the year have a minor alteration to the checksum code - the code calculated above is 1 too large. It is not certain at this point if the same calculation is carried out and 1 subtracted or if the code is calculated with a different modulus.

	=== Code ===		=== Code ===

@@ Line 56: / Line 56: @@
     checkdigit = (12 - (s mod 11)) mod 10
 end function
 </pre>

@@ Line 42: / Line 42: @@
 ==== Basic ====
-This Basic program (suitable for calls from MS Excel or OpenOffice Calc, calculates the check digit:
+This Basic function (suitable for calls from MS Excel or OpenOffice Calc), calculates the check digit:
 <pre>