## What a teacher can make [Video]

This is a very emotional and touching video about how much difference a teacher can make to a student’s life:

Yet another impressive movie is that one based on “Three Letters from Teddy” story .. Watch it here: *http://www.makeadifferencemovie.com/*.

## XOR – The Interesting Gate

*Note: The interesting features in XOR and XNOR are somehow the same but with small difference, I’ll speak in details here about XOR and will provide another article for XNOR later.*

Among other logic gates, XOR and XNOR are interesting gates having some unique features.

### Multi-input XOR

All 2-input logic gates have the same meaning when they have more than 2 inputs. For example an AND gate is a gate that outputs 1 when all its inputs are 1, an OR gate outputs 1 when any of the inputs is 1, a NAND gate outputs 0 when all its inputs are 1, a NOR gate outputs 1 when all its inputs are 0.

A 2-input XOR gate outputs 1 when there’s exactly a single 1 at the inputs which means it’s exclusively there and that’s from where the name XOR (Exclusive OR) comes. We can alternatively say that it outputs 1 when the 2 inputs are different.

A multi-input XOR gate however doesn’t necessarily have the same meaning as the 2-input XOR above. There’re two different interpretations for a multi-input XOR and let’s check that on a 3-input XOR as an example:

## How many things between X and Y?

I’ve noticed that there are 3 possible answers for the question “How many things between X and Y?”.

I’ll give 3 examples to explain what I mean:

1. How many hours do you take between 2 PM and 7 PM?

The answer is **5** hours which is **7-2**.

2. How many numbers are there between 2 and 7?

The answer is **4** numbers (The numbers 3, 4, 5, 6) which is **7-2-1**.

3. How many numbers would you speak out if you count from 2 to 7?

The answer is **6** numbers (The numbers 2, 3, 4, 5, 6, 7) which is **7-2+1.**

**So why is the answer different in each case?**

In the first question, you are asked to count the number of hours between 2 and 7. Actually the hour meant in the question is a period. From 2 to 3 is a period of hour, from 3 to 4 is another period and so on. The answer then is Y-X that gives you the number of steps (periods) that you’ll take from X to Y.

In the second question, you are asked to count how many numbers there are between 2 and 7. This time you’re asked to count the numbers themselves that you would visit between 2 and 7 … not the steps you’ll take. If you’re taking 5 steps from point 2 to point 7, then there are 4 points between them (that’s excluding the first and last point). So the answer is Y-X-1.

In the third question, it’s asked to count numbers that you speak out when counting from 2 to 7. This is to say in other words, “How many numbers between 2 and 7, inclusive?”. Let’s conclude the answer in a new style … Do you mind that a one step forward needs 2 points and 2 steps forward need 3 points and so on…? This is true! … Well if you got how I explained the answer of question 1 then the answer to this question is Y-X+1 because the number of steps is Y-X between X and Y!

**Conclusion**:

The answer for the question “How many things between X and Y?” is either Y-X, Y-X-1, or Y-X+1 and the answer depends on what things you are trying to count!

## IEEE Activity: ACM Training Program

One of the activities of the IEEE Student Branch at the Faculty of Engineering at Shoubra is the ACM Training Program. Students meet together once or more every week in the faculty to be trained on Algorithms and Problem Solving techniques.

The training started on January after holding some qualification exams. So far it has shown a great advancement.

As an example, we have got some pictures and videos of one day of our activity below:

And this is the photo album of this day:

## Programming language?

**Programming languages**

What is a programming language and why do we need it? – An important question that we will try to answer below together.

## How many primes are there?

**Prime number **is a natural number greater than 1 and has exactly 2 divisors, 1 and itself.

The first few prime numbers are 2, 3, 5, 7, 11, 13, 17 …

The question is, How many primes are there? or in other words, is there a finite number of primes?

The answer is NO, there are infinite number of primes and we are going to prove this below together.

## √2 is irrational

**Prove that √2 is irrational number i.e. it can not be represented as a fraction a÷b where a and b are integers, b>0.**

*This is a very clever proof as a practice on proof by contradiction.*

If you believe that √2 is a rational number, then I’ll ask you to come with this fraction **a**÷**b** but first reduce it to lowest terms. And I’ll convince you at the end that **a** and **b** must be both even. Does this mean you are a liar? 😉 – No it just means that there is a contradiction and thus √2 can not be rational (and that **a**÷**b** you have suggested is a fake! 😉 ).

## Recent Comments