How can you explain the difference between an interface and an abstract class to a non-programmer? [duplicate]

Answer 1

For everything computer related, I use a cooking dinner example. I start by saying that hard drives are cabinets/storage closets. Memory is like your counter. Processor is the cooking apparatus (stove). You are like the system bus (moving things around, etc...). So when you boot a computer, you take your basic ingredients out of storage and put them on the counter (loading the OS). This is a loose example, but it works well.

Now to move into OOP: an ingredient is an object, so is a tool (bowl, knife, spoon, etc...). Each one of these has properties (knife= handle_color: black, blade_type: serrated, etc...). And each one has methods/actions that you can perform with them (knife = cut(pepper)).

Now you can take this as far as you want to. For instance, there are green, yellow and red peppers. Each one is a pepper, so you can say "inherit the pepper class" (layman: take everything you know about a pepper and apply it to this specific pepper, pepper has a color attribute, a red pepper is color=red).

You can even separate class from instance (this particular pepper is an instance, whereas on the recipe card it's a class).

So you could make some pseudocode:

class pepper {
    var color
    var spiciness
    var size
}

class redPepper extends pepper {
    construct(){
        $this->color=red
    }
}

class cuttingKnife extends knife{
    construct(){
        $this->blade_type=serated
    }
}

class cookingPot extends pot{
    construct(){
        //We all know what a cooking pot is
    }
}

class stove extends apparatus{
    construct(){
        //We all know what a stove is
    }
}

$knife = new cuttingKnife();
$myPepper = new redPepper();
$pot = new cookingPot();
$stove = new stove();

$knife->cut($myPepper);
$pot->putOn($stove);
$stove->cookOn("high");
$pot->putIn("water");
$pot->putIn($myPepper);

//This will boil a cut pepper

Of course, people won't necessarily understand the pseudocode, but they would understand how to boil something. They would understand the difference between a "pepper" and a "red pepper". I think you can pretty much use this analogy for any computer related thing with some minor tweeks.

• multithreading: add more burners to the stove and another cook in a single kitchen
• multicore arch.: add a second kitchen
• downloading/installing software: go to store, find food, bring home, deposit in storage
• partitioning a HDD: different cabinets/fridge could be Linux proc system (because it's special).

Etc...