Archive for category Lessons

Let’s Learn JavaScript • Lesson 3 • Beginning JavaScript

📅 July 19, 2017
Continuing from the exciting Hello, Galaxy! HTML file we wrote in the previous lesson, let’s add some JavaScript to show a popup dialog and write text to the page.

 

 
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Let’s Learn JavaScript • Lesson 2 • Basic HTML 5

📅 July 14, 2017
Client-side JavaScript requires a knowledge of HTML, so this lesson will focus on building a minimal HTML 5 file that we can use for writing JavaScript.

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Let’s Learn JavaScript • Lesson 1 • Introduction

📅 July 13, 2017
Have you ever entered text in a search engine and noticed suggested results appear as you type? That’s JavaScript.

Have you scrolled through a web page of images and observed new images added to the page as you scroll towards the bottom of the page? That’s JavaScript.

 

Have you watched forms display a red border or error message as you finished entering a credit card number? That’s more JavaScript.

Have you ever thrown up your hands in anger as annoying popups littered your desktop with mind-jarring, blinking ads accompanied by new browser windows that expand to fullscreen in order to advertise an online survey? That, too, is JavaScript.

JavaScript is a programming language that produces dynamic web pages. If you have ever wanted to learn how to perform this mysterious magic in JavaScript, then here is the first lesson that introduces the background of this fun language.

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Binary Lesson 17 – Parity

📅 March 4, 2015
lesson17The word parity originates from the Latin word par, meaning equal. Take the sport of golf, for example. A hole on a golf course is usually assigned a par number. If you sink the golf ball into the hole with the same number of strokes as the par, you are said to be on par — equal to the number of expected strokes. If you expend more strokes than the par, then you need practice, and you should probably try again.

An identical strategy applies to computers. Parity is an early form of error detection often used with serial communications, such as modems and serial ports, for example. An extra bit is appended to each data byte to make the total number of 1 bits even or odd. This extra bit, called the parity bit, is separate from the data byte, and it does not contain data information. It is only used to make the total number of 1 bits even or odd.

There are two main types of parity: Even parity and odd parity. Both operate in the same manner aside from the evenness or oddness.

This lesson focuses on 8-bit data even though the concept can apply to any number of data bits, such as 7-bit ASCII.

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Binary Lesson 16 – Binary Logic

lesson16A digital logic gate accepts input and produces a Yes or No output based upon a condition. Examine a light switch with two switches in the pseudo-electronic schematic below.

 

 

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Demonstration of binary logic AND.

In order for the light to turn on, both switches must be on, but if either switch is turned off or if both switches are turned off, then the light is off.

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Binary Lesson 15 – Binary Division

📅 November 18, 2014

lesson15Binary division is an excellent way to practice an understanding of bits and binary values. Is one binary value larger than, smaller than, or equal to another?

This requires a good understanding of the binary place value system, and the better it is memorized, the easier binary division will be.

Also, binary division offers extensive practice with binary subtraction. We saved binary division until after we had introduced at least two methods for binary subtraction because the most involving part of binary division is the subtraction itself.

Sometimes, we must also add a radix point for values not easily divisible by the given number. If this happens, keep in mind that an exact value might not be possible, as in the case of irrational numbers, so it will be necessary to stop at a certain number of digits for a close approximation. The exact point at which this occurs will depend upon experience…or if your fingers get tired, or if you run out of pencil lead, or if you get lost in the seemingly endless series of zeros.

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Binary Lesson 14 – Subtraction Using Two’s Complement

November 3, 2014

lesson14In Lesson 10, we saw how to perform binary subtraction using a set of rules for each column of bits.

Now that we have seen how to use signed numbers in binary, we can subtract in binary by performing algebraic addition using the two’s complement method.

Neither technique is more correct than the other. They are two different ways that produce the same result.

Personally, I find the two’s complement method to be easier to compute than the longhand method. It might sound conflicting to “subtract” by “adding,” but that is what we are doing when we add two signed numbers together with opposite signs. (+5) + (-3) = 2, which is the same as 5 – 3 = 2. Same result, but two different thought processes.

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