How do binary and hexadecimal numbers work?

This post is from a series I'm writing in which we'll learn how computers work, by writing a computer simulator in Javascript. However, I figured an explanation of binary and hexadecimal numbers is useful enough by itself, so here it is!

Before explaining how computers load data into their working space and process it, it's valuable to understand binary and hexadecimal numbers. This is because computer hardware only understands binary values due to the physical characteristics of the electronic circuitry used to implement them. I won't go further into explaining the reasons why computer hardware works with values in binary form, but you can read more about it here.

So what is binary? Binary is a 'base-2 number system'. But what does that mean?

Running a Hypercard stack on a modern Mac

Hypercard in SheepShaver emulator

Updated: now works on Yosemite

A bunch of people have emailed me about getting Hypercard stacks running under emulation. Here is a pretty easy guide to running a Hypercard stack on a recent Mac (eg. running Mavericks, Mountain Lion, etc):

Place the Hypercard stack you want to access somewhere within your user folder: eg. Documents, or Desktop.

Download this zip file [95mb] containing the SheepShaver classic Mac emulator bundled with Mac OS 9 and Hypercard.

Extract and open hypercard.sheepvm. This should boot Mac OS 9.

On the Mac OS 9 desktop there should be a disk called "Unix". This is a virtual disk which actually lets you access files on your computer (eg. outside the emulator). Opening it is equivalent to opening your OS X /Users/ directory.

Why port emulators to the browser?

MacPaint Woodblock sample image

In a discussion on Hacker News about emulators being ported to the browser, I drew attention to my own project, PCE.js, which emulates a Macintosh Plus and an IBM PC/XT. Some of the questions brought up included why someone would undertake such a project, and also the legal considerations of including the software ROM required to boot the machine.

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