Replaced stock photos, deleted old images.

Added examples of wrist watch designs. Some typo corrections.

docs/courses/csintro/binary.md

@@ -1,11 +1,13 @@
 # Binary
 
+![Binary numbers shown on a monitor](/static/courses/csintro/binary/binary-crt.png)
+
 This lesson presents the concept of binary digits and base-2 notation.  Students will learn how data is stored digitally and how it can be read and accessed.
 
 ## Lesson objectives
 
 Students will...
-* Understand what a bit and byte are and how they relate to computers and the way information is processed and stored.
+* Understand what bits and bytes are and how they relate to computers and the way information is processed and stored.
 * Learn to count in Base-2 (binary) and translate numbers from Base-10 (decimal) to binary and decimal.
 * Apply the above knowledge and skills to create a unique program that uses binary counting as an integral part of the program.
 

docs/courses/csintro/binary/project.md

@@ -37,6 +37,13 @@ An implementation of the Binary Cash Register
 * To make the strap of the wristwatch, put 2 pieces of duct tape back-to-back, and use velcro tabs as the fasteners
 
 ![Binary wrist watch project](/static/courses/csintro/binary/binary-wrist-watch.jpg)
+To make the strap of the wristwatch, you can put two pieces of duct tape back-to-back, and use Velcro tabs as the fasteners.
+
+![Holder](/static/courses/csintro/conditionals/holder.jpg)
+This is a holder that allows the micro:bit to be worn on the wrist.
+
+![Wooden structure to hold the micro:bit on the wrist](/static/courses/csintro/conditionals/microbit-holder.jpg)
+This design supports the micro:bit in a rigid cradle and allows more delicate connections to the pins.
 
 ## Reflection
 Have students write a reflection of about 150–300 words, addressing the following points:

docs/courses/csintro/binary/unplugged.md

@@ -23,7 +23,7 @@ If you have time, create on a poster board, on the whiteboard, or on paper as a
 
 You can also just make a very simple vending machine diagram like the one below:
 
-![Vend-o-matic diagram](/static/courses/csintro/binary/vendomatic.jpg)
+![Vend-o-matic diagram](/static/courses/csintro/binary/vendomatic.png)
 ### ~
 ## Introduction
 Ask the students the following questions to spark discussion:
@@ -105,7 +105,7 @@ Hand out the 32 unit coins, one to each student or pair of students.
 * What is the new maximum price you could pay for an item? _63_
 * What combinations of coins can you use to pay for an item priced from 32 units to this new maximum price? 
 
-![Coins representing binary digits](/static/courses/csintro/binary/coins-as-digits.jpg)
+![Coins representing binary digits](/static/courses/csintro/binary/binary-place-values.png)
 From coins to binary notation - the number 45
 
 Once students are comfortable making combinations of numbers, encourage them to use ones and zeroes to represent the numbers instead. This number system uses the number 2 as its base (each place is two times the one before it.) It is called the Base-2 system, or binary system. The number system we are normally familiar with is the Base-10 system, or decimal system (each place is ten times the one before it.)