User-Friendly Expression of Information

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In this episode, you will learn about user-friendly expression of information. What does that mean? Information is data. This episode talks about how data is represented in software, including variables, memory, and more.

Your key takeaways are:

Variables:
- represent data
- are user-defined – meaning you name them what you want (within reason)
Quality Tip: purposefully name your variables to describe the data it represents
Variables are stored in a memory location and then hold the location to where the data is stored

Study Notes

Imagine language where you spoke in data instead of generic names. What do these numbers mean?

	2014	2015
October	90,512	79,436
November	128,039	98,180

What does this number mean?

“Compared to last year, my store has declined 40,935.”

Imagine Coding in Data

if ( 98180 - 79436 > 218551 ) { printReport(); }

What do the numbers mean?
These numbers are now fixed (hardcoded)
These numbers cannot vary
The threshold cannot be adjusted without editing the code

Variables

Thought experiment: What is common about the data above?

In software, we say data is variable.

Not constant
Varies
On its own, it lacks context

Variables Represent Data

User defined names
Language requirements:
- begin with a letter
- no symbols
- unique (to the scope)
- not a reserved word (keyword)
Quality code tip:
- Name the variable for the data it represents
- Give it a meaningful and purposeful name

By adding the label Units Sold, is this table more meaningful than the one above?

Units Sold	2014	2015
October	90,512	79,436
November	128,039	98,180

Variables in Action

	// $unitsSold has the data from the database
	$totalUnitsSoldInQ4 => array(
	2014 => $unitsSold[2014][10] + $unitsSold[2014][11],
	2015 => $unitsSold[2015][10] + $unitsSold[2015][11],
	);

	if ( $totalUnitsSoldInQ4[2015] < $totalUnitsSoldInQ4[2014] ) {
	printReport();
	}