1. Coding Concepts (Basics)
Topic 2: Programming
Coding Concepts (Basics)

2. Developing Code
We’ve seen how to both analyse problems and evaluate solutions
Both of which can be done before we put code to file
If we want to implement a solution, we’ll eventually have to program something
For this course, knowing how to program isn’t the only thing we need to know
We also need to learn the following:
Fixing possible errors
Using coding constructs
Using correct data types/structures
Writing descriptive comments
Creating sub-programs
Validating user input
Programming: Coding Concepts (Basics)

3. Programming: Coding Concepts (Basics)
Developing Code
The first thing to note is that you have a choice of programming language
Out of: C#, Java, and Python
You are free to pick any of these three
Coding examples will be given for all languages
Choose the one that you are most comfortable with
The following topics are used in all three
Programming: Coding Concepts (Basics)

4. Programming: Coding Concepts (Basics)
Developing Code
The second thing to note is how we define a program in the different languages
Java and C# does this easily
Create project/solution acts as a single program
A file can be added (usually automatically) that acts as the starting point of the program
Inside of which is a main() function
Python is a bit more freeform
The file itself acts as the entry point
No need for a main() function
But one can be added
Programming: Coding Concepts (Basics)

5. Programming: Coding Concepts (Basics)
Developing Code
Python C#
Java
In Python, we don’t need to create a main function. However, if we were to create larger Python programs later on (which may require multiple Python files), having floating code (instructions not in any scope) is actually a bad thing. When importing a Python file for use in another file, floating code is actually run as well (not just ‘included’).
This means we could accidentally run a different program when importing a Python file. Including the if __name__ == ‘__main__’ check means that we only run that function if and only if the script itself is being run, not when it is imported into another file.
Programming: Coding Concepts (Basics)

6. Programming: Coding Concepts (Basics)
Coding Constructs
All procedural programs are built off three important ‘pillars’
Sequencing
Branching
Iteration
These are known as constructs
They each describe a certain action (or series of actions)
They can be implemented in different ways (with different techniques)
Programming: Coding Concepts (Basics)

7. Coding Constructs: Sequencing
This is the act of running instructions one after the other
Running them “in a sequence”
This is the simplest construct to use
All we have to do is do things in the program
Branching and Iteration are used via Sequencing
Programming: Coding Concepts (Basics)

8. Coding Constructs: Sequencing
This simple example includes creating variables and storing values in them
Sequencing is as simple as running one instruction after another
Python
C#/Java
Programming: Coding Concepts (Basics)

9. Coding Constructs: Branching
This is the act of choosing specific instructions to run (sequences)
Based on a condition (a boolean expression)
Branches can be introduced via four different techniques
If statements Else statements Else-If statements Switch statements
If, Else, and Else-If can be used together
Need at least one if-statement
Can have as many else-if statements as we want
Can only have one else-statement at the end
Programming: Coding Concepts (Basics)

10. Coding Constructs: Branching
This example checks to see if the user entered yes or no to a question
Python
Java C#
Programming: Coding Concepts (Basics)

11. Coding Constructs: Branching
Switch-statements are used on their own
Not part of any other technique
They can take in any numerical value
And then check possibilities of that value (known as cases)
Note three important things
Switch-statements only check for equality
Cases in a switch-statement need to be broken out of (to stop trickle down)
Switch-statements are not in Python
Programming: Coding Concepts (Basics)

12. Coding Constructs: Branching
Here’s the same example from earlier (using a switch-statement this time) C#
It’s the same in C# as it is in Java (except for the differences in how output work).
Programming: Coding Concepts (Basics)

13. Coding Constructs: Iteration
This is the act of repeating sequences based off of a condition
Iteration is used when we want to repeat a sequence
A set number of times (within a specific range of values)
Indefinitely (until a condition returns false)
We have two techniques for using iteration
For-loops While-loops
For-loops have more control (we use them when we know how many times to repeat)
While-loops are for more indefinite loops
Programming: Coding Concepts (Basics)

14. Coding Constructs: Iteration
Here’s an example of using a for-loop to search for a value in an array
Python C#
Programming: Coding Concepts (Basics)

15. Coding Constructs: Iteration
Here’s an example of using a while-loop to keep a program running until the user wants to stop
Python C#
Programming: Coding Concepts (Basics)

16. Programming: Coding Concepts (Basics)
Coding Constructs
Those are all the constructs that a program can use to solve different problems
Knowing which technique to use at a certain point is fundamental to creating good programs
For example, should we use a for-loop instead of a while-loop?
We also have other things, like data-structures and sub-programs to look at
Will come later
Programming: Coding Concepts (Basics)

17. Programming: Coding Concepts (Basics)
Create the following programs in your programming language of choice
Given an array of positive integers, find the smallest positive integer that does not appear in the array
Given an array of integers and an integer, output “Yes” or “No” depending on if two integers in the array add up to the given integer
For exercise 1:
Imagine having the array [1, 6, 3, 8, 9, 5]. The program should say 2 (because it’s the first positive number, starting from 1, that is not in the array).
For exercise 2:
Imagine having the array [1, 4, 8, 2, 9, 10], and the number 6. The program should say “Yes”, because the array contains 4 and 2, which add up to 6.
Programming: Coding Concepts (Basics)