2. We’re moving on to more recap from other programming languages
Variables in C++
We’re moving on to more recap from other programming languages
Starting with variables
Most are the same
Two have big differences

3. Variables in C++ (1) We have the usual suspects int: a whole number
double: a decimal number
float: a smaller decimal number
char: a character
bool: true/false, 0/1

4. Variables in C++ (1) Ex Open Visual Studio 2015/2017
Create a New solution for C++
Make it an Empty Project
Add the main() function
Make it return 0
Create each of the following variables (and give them values)
int, double, float, char, bool

5. Variables in C++ (2) The only one missing is string
Unlike some other programming languages, string is NOT a primitive type here
It has no ‘keyword’ like int or double
In fact, for a while, there was only one way to make them
Arrays of characters

6. Variables in C++ (2) Still starts as a char
[] not added until after variable’s name
Can still use “” to denote a string though

7. Variables in C++ (2)
However, creating arrays for strings is cumbersome
So, a quicker way of making them was created
Added to C++ as an update
Using the string library

8. Variables in C++ (2) We can include the string library at the top
This lets us use the string data-type
Like other programming languages
Still use “” to denote strings
Note that string is a different colour to other keywords – there’s a reason for that, which we’ll find out this term

9. Include the string library at the top of the C++ file
Variables in C++ (2) Ex
Include the string library at the top of the C++ file
Create a string variable for your name
And give it a value

10. The arrows (<< and >>) show data flow
Variables in C++ (3)
We can output these variables to the console
However, printf doesn’t play well with string
So we can use cout
Uses slightly different syntax
More like concatenation than formatting from before
The arrows (<< and >>) show data flow

11. The arrows (<< and >>) show data flow
Variables in C++ (3)
One thing to note about cout
It doesn’t support formatting like printf
If needed, we can output string in printf
Using name.c_str()
The arrows (<< and >>) show data flow

12. Variables in C++ (3) Ex Output each of your variables to the console
Use cout to do this
Part of the iostream library
Use << to concatenate text/values
Don’t forget the \n at the end

13. Variables in C++ (4) The final thing is getting a string from the user
Can’t use scanf_s
Same reason why printf doesn’t work
So, we use cin instead
Same as cout
But data flows in opposite direction

14. Variables in C++ (4) Be careful about the direction of the arrows!
This will be the preferred way of outputting/inputting for now.

15. Use cin to get a value for each of your variables
Variables in C++ (4) Ex
Use cin to get a value for each of your variables
Make sure the arrows are pointing the right way
Output these to the console after to check they are all correct

16. Now we have two main aspects to recap
Branching (1)
Now we have two main aspects to recap
Branching
Iteration
Both are core constructs in many other programming languages

17. Branching (1) Branching involves running different instructions
Depending on a condition
Like other languages, we have techniques for these
If, else-if, else
Switch

18. Branching (1) Note that the usual rules of if/else-if/else apply
Need to start with if
(OPTIONAL) Can have as many else if as needed
(OPTIONAL) The else goes at the end

19. Branching (1) Ex Comment out the inside of the main() so far
Can use block comments at the start and end
Use /* and */
Ask for the user’s age
Check their age for the following (and output the respective message)
< 20: Still growing
< 40: You’re an adult now
< 60: Getting on to middle-aged
Otherwise: Enjoy retirement when/while you can

20. Branching (2) The other technique was the switch
It takes a single numerical/enum value
And compares it against many cases
Note that they only check for equality
No less than/greater than here

21. Branching (2)
Note that each case requires a break at the end
Can also add an else by using the default label

22. Branching (2) Ex Comment out your main() so far
Ask the user what symbol is used for logical OR
Use a switch to check for
|: That is correct!
+: In some cases, yes!
Otherwise: Not quite! The answer is “|”

23. Iteration (1) Next up is iteration The two techniques we have for this
while-loops
for-loops
They both behave like they have done in other languages

24. Iteration (1) Let’s start with the while
It repeats its scope until its condition returns false
The scope contains all the code within the curly braces
While-loops are best used for “indefinite” instructions
That could go on forever

25. Iteration (1)
This program turns a number into that letter of the alphabet
The while stops the number from being invalid

26. Iteration (1) Ex Comment out your main() so far
Ask the user to accept/decline an agreement
Get their input in char form
Show them options for (y/n)
Use a while to make sure they enter one of those options
If they didn’t, ask them again
After the while, either thank them for agreeing or say “Maybe next time” if they declined

27. The other technique is the for
Iteration (2)
The other technique is the for
This gives us a bit more control than a while
Still repeats based off a condition
But we can also create a counter and change it at the end of every loop

28. Iteration (2) This program outputs a right-angled triangle
Gets a size from the user
Outputs a triangle of that size

29. Iteration (2) Ex Comment out your main() so far
Ask the user for a size of a square
Use for-loops to output a hollow square
Outside formed of “0”s
Inside formed of spaces

30. Random Numbers
The final useful thing to cover before we look at some programs
Making random numbers
Other languages have us make a random number generator
We don’t need to do that here
Simply run a single function
However, still have some setup

31. This requires three things
Random Numbers
This requires three things
Including the time.h library
Using srand() to use a specific seed
Using rand() to make a random number (and limiting it via a modulo)

32. Random Numbers The modulo is the best way of limiting rand()
Only adds a maximum
Need to ‘shift up’ if we want to make a minimum
The srand() function sets the seed
And time() gets a time
Using NULL makes time() uses the system time
In total makes sure seed is always changing

33. Random Numbers Ex Comment out your main() so far
Include the time.h library, and use srand()/time() to make a seed
Generate a random integer
Output a message if the number is even/odd

34. Higher or Lower Ex Create a new C++ solution
This solution should be the Higher or Lower program
First the program generates a random number (0 – 100)
Then the program repeatedly
Asks the user for a guess
If the guess is too low/high, one message is output
If the guess it spot on, the game ends

35. END OF UNIT!