RSA Encryption: A fully featured demo tells you all you want to
know about the mathematical backgrounds of RSA encryption. The demo is
totally interactive and starts with prime generation, key generation and
coding & decoding messages. Download
Bits & Binary Arithmetic: This demo is very simple and shows
you how binary digits represent numbers. Checkboxes can be checked and
unchecked to illustrate bits, and the numbers reflected by those bits.
Download
Day Calandar: The worksheet contains two Calandar ActiveX controls
showing you the ordinal number of any date in the 20th and 21st century.
Select your day of birth and today to know how many days you lived so far.
Download
Hashing: This demo shows you what hashing is, and how it works.
Simply give an input string and a hash character is returned and stored in a
hashtable. Also collision handling is graphically illustrated.
Download
Log File Analysis: The program can import any kind of log file into
Excel, determine the fields and create an analysis of each field on a
seperate worksheet having the name of the field analyzed. Of each field
value the occurence is counted and put into a sorted table.
Download simple or advanced
workbook.
Cephes: Learn how to make the wonderful Cephes library full of
mathematical functions available in your Excel VBA applications. Reference
CEPHESlib as an object, instantiate the CEPHESlib class and use its
encapsulated functions. This example teaches you how to implement the gamma
and error function and many more.
Download
Hanoi Towers: Unleash the full potential of recursive programming
by playing this fully interactive game in a simple Excel spreadsheet and see
how you can simply reduce the problem size by recursively calling a smaller
problem of the same type twice. Play it and see the consequences.
Download
Unprotecting Worksheets: You protected your worksheets with a
password you already forgot? No problem, this workbook provides you with the
VBA code to unprotect the sheet. The basic idea is that all worksheet
passwords are hashed before being stored, while there are "only"
194560 hash values to be tested to exhaust the value space. Download
Large factorials: Calculate very large integer factorials without
overflows! How come? Simply add logarithms instead of multiplying integers
and derive the mantissa and the exponent of the logarithm sum. Results are
given in scientific notation. Download
Random sequence: Generate a random string consisting of digits in a
predefined range and having a predefined length. Also suitable for
generating bits strings. Download
Chaos: In this workbook the quadratic function f(x) = x^2-c^2+c is
iterated for a range of values of c. For some values of c, there is only one
limit value, for other values two, four or more. After eliminating
initial oscillations, the plots yk(x)
= f250+k(x)
are plotted against c, so the pairs (yk,c)
are plotted. The resulting graphs are called bifurcation
diagrams. For c between 1.78 and 1.79 the chaos begins… Download
Integration & Differentiation: In this workbook it is very easy
to calculate integrals and derivatives of any function of variable x. You
only have to enter the function into a textbox instead of altering the
function in the VBA code. Special thanks go to Jay Petrulis for providing
source code at module level. Download
Continued Fractions: Always wanted to know about the Golden Ratio,
being defined as a/b = b/(a+b)? Well setting a to 1 yields
b=0.5*SQRT(5)+0.5=1.61803398874989=1 + (1 / 1 + (1 / 1 + (1 / 1 + (1 / 1+ (1
/ 1 + (1 / 1 + (1 / 1+...))))))). In fact any decimal number x can be
written in the form x=a + (1 / b + (1 / c+ (1 / d + (1 / e + (1 / f + (1 / g
+ (1 / h+...))))))). Some series end, some don't. Curious? This demo gives a
great graphical representation. Download
Finite automata: This code shows you the basic principles about
building a parser, derived from a finite automaton. Once you have designed
the finite automaton, which is essentially a graphical representation, of a
certain type of string, it is easy to transform it into an algorithm which
is called a parser. Download or view
source code. Download workbook.
Prime numbers: Calculating prime numbers can be done very fast
using the Sieve of Eratosthenes. Deleting numbers that are definately not
prime is much faster than testing divisors of a range of numbers. See how it
works in this great demo. Learn both the principles and make a calculation.
Writing 2,3,5,7,11,13,...,999983 to a worksheet is a piece of cake in less
than a minute. Download