1. Coding Concepts (Sub- Programs)
Topic 2: Programming
Coding Concepts (Sub- Programs)

2. Creating Sub-Programs
We mentioned when designing solutions that we can break our solution into smaller pieces
Known as sub-programs
We can do the same thing in a program
We can take pieces of logically separate code
And put them into separate places
These sub-programs are referred to as procedures and functions
Programming: Sub-Programs

3. Creating Sub-Programs
There is a difference between these two terms
Procedures: sub-programs that do something
Functions: sub-programs that return information
We create procedures any time we want to run a series of instructions multiple times
Like outputting data to the console
We create functions any time we want to calculate something multiple times
Like calculating the distance between two points
Programming: Sub-Programs

4. Programming: Sub-Programs
Creating Procedures
Let’s start by creating a procedure
Java
Python
In Python, we start procedures with def (define). We then give the procedure a name and some brackets. The code indented after belongs to the procedure and is run when the procedure is run.
C# and Java use the same syntax for making a procedure, but use curly braces instead of indentation for its code. C#
Programming: Sub-Programs

5. Programming: Sub-Programs
Create a program that contains two procedures
Procedure 1
Asks for the user’s name, and says hello to them
Procedure 2
Asks for the user’s height, and outputs whether they are too short or tall enough to ride a rollercoaster
The rollercoaster has a height requirement of 1.4 metres
Programming: Sub-Programs

6. Programming: Sub-Programs
Creating Functions
The difference between a procedure and a function is that a function needs to return some information
Typically, functions will return a value of some kind (relevant to the function)
For example, we’re making a function that calculates whether a number is prime
Since this is a “yes or no” question, the function should return a boolean
Programming: Sub-Programs

7. Programming: Sub-Programs
Creating Functions
Here’s an example of creating a function that randomly generates either true or false
Java C#
Python
The important bit here is the use of the keyword return. This takes the value to its right and moves it to where this function was called.
Programming: Sub-Programs

8. Programming: Sub-Programs
Create two functions in your program
Function 1
Generates a random number and returns whether it is even or odd
Function 2
Generates a random width and height for a rectangle, and then returns the area of that rectangle
Programming: Sub-Programs

9. Programming: Sub-Programs
Using Parameters
Not all functions can, or need, to generate random numbers
Sometimes maybe we want to specify the value a function uses
We may want to do the same thing with a procedure
This is where we can make use of things called parameters
These are values that can be passed in to the procedure/function for it to use
Programming: Sub-Programs

10. Programming: Sub-Programs
Using Parameters
For example, whenever we generate a random number, we can put an upper/lower bound on it
This number that we type in gets passed to a parameter in that function
On a side note, we call values that get passed in to parameters arguments
The number 101 here is an argument. It gets passed into a parameter of this function Next()
Programming: Sub-Programs

11. Programming: Sub-Programs
Using Parameters
We can include parameters in procedures/functions simply by adding variables to the brackets
After the procedure’s/function’s name
This follows the same variable standards/syntax as the rest of the programming language
Python: only need to include a name
C# and Java: need to include a data-type and a name
Programming: Sub-Programs

12. Programming: Sub-Programs
Using Parameters
Here is an example of the rectangle area function, but this time using parameters
These are all simple functions
Some procedures/functions we make may be more complex
For example, we could make a function for any of the sorting/searching algorithms
Python C#
Java
Programming: Sub-Programs

13. Programming: Sub-Programs
Add one more function and one more procedure to your program
Function
Takes a base and a height (integers), and uses them to return the area of a triangle
Procedure
Takes an array of integers and outputs them, on the same line, to the console (with square brackets [ ] around the numbers)
E.g. [1, 5, 3, 7]
Programming: Sub-Programs

14. Programming: Sub-Programs
Global Variables
In any program, there may be a value we want to keep track of over the whole program
Not just in a single procedure/function
Any variable we create inside a procedure/function is known as a local variable
As it can only be used inside that procedure/function
Two variables, with the same name in different procedures/functions, are considered entirely different
If we make a variable outside of any procedure/function, it is global
Any procedure/function can use it
Programming: Sub-Programs

15. Programming: Sub-Programs
Global Variables
Python
Java C#
Note that Python needs to include global before the global variable’s name in a procedure/function. This is only needed if that variable’s value will change (but it’s safe putting it in even when its not).
Java and C# make/use the variable as normal, except for the added public static in front of it (like a procedure/function).
Programming: Sub-Programs

16. Programming: Sub-Programs
Operators
We should also take the time to recap the different operators we can use in Python, C#, and Java
They each have access to the same operators, and are handled largely the same way
These operators are split into three categories
Arithmetic Operators: +, -, *, /, %, // (Python only)
Relational Operators: ==, <, >, !=, <=, >=
Logical Operators: and/&&, or/||, not/!
Programming: Sub-Programs

17. Programming: Sub-Programs
Operators
Arithmetic Operators
+: Addition (adding the left and right sides)
-: Subtraction (subtracts the right side from the left)
*: Multiplication (multiplies the left and right sides)
/: Division (divides the left side by the right)
%: Modulo (calculates the remainder from dividing the left by the right)
// (Python only): Integer division (returns the division result as an integer)
Logical Operators
&& (and): Boolean AND (true if both left and right sides are true)
|| (or): Boolean OR (true if either left or right sides are true)
! (not): Boolean NOT (true if right side is false)
Programming: Sub-Programs

18. Programming: Sub-Programs
Operators
Relational Operators
==: Equals (returns true if left and right sides are the same)
<: Less-than (returns true if the left side is smaller than the right side)
>: Greater-than (returns true if the left side is greater than the right side)
!=: Not-equal (returns true if the left and right sides are not the same)
<=: Less-than or equal-to (returns true if the left side is smaller, or the same, as the right side)
>=: Greater-than or equal-to (returns true if the left side is greater, or the same, as the right side)
Programming: Sub-Programs

19. Programming: Sub-Programs
Create a program that generates an array of random integers, outputs them, sorts them, and outputs them again
However, put the array generation, array output, and array sorting in different functions/procedures
Programming: Sub-Programs