Program Coding and Implementation

After the design phase, the next phase in developing software solutions is to write a program or code.
- A program is a set of instructions in a computer language intended to solve a problem. (Implement an algorithm)
- The task of translating an algorithm to a program is called programming or coding.
Programming uses a number of tools.
- You need a way to put the computer code into a file.
- C++ is known as a high level language, you need a way to translate that high level language into a language that the computer can process.
- We will be working in a client server environment, so you will need tools to move the code from your computer to the server.
- You will also need a way to tell the server what to do.
I will attempt to demonstrate the process by solving coding the algorithm we just developed.
But there are several problems.
- I will discuss one set of tools
  - Some of these are optional, you could use others.
  - Some of these are required, you must use the one I select.
- I will try to point out where you have a choice.
Step 1, Editing
- A text editor is a program that allows you to put text into a file.
  - Word is not a text editor, it is a document preparation system.
  - Notepad is an insufficient text editor.
- For text editors we do not care about bold, italics, ... only text.
- You have many choices for text editors. (I doubt that this list is complete)
  - I will demonstrate a program called Notepad++
  - But I understand that Visual Studio Code is an outstanding choice.
- Generally you would like something that
  - Deals with code well.
  - Works for you
- I use an editor called vim, but that is somewhat difficult.
  - I would not necessarily recommend this.
Let's enter some code in notepad++.
- These two lines include some libraries.
  - ```
  #include <iostream>
  #include <string>
         
```
- You will learn more about this in 230, but for now, we will need them in all programs that we write.
- The next line is also required
  - ```
  ...
  #include <iostream>
  
  using namespace std;
              
```
- This is a real c++ command.
- We call it a statement.
- All statements end with a semicolon ;
- Notice I left a blank line between the includes and the using statement.
- This is to improve readability.
  - This is a matter of programming style.
  - Generally blank lines, spaces and tabs don't matter to the computer
  - These characters are called whitespace
  - But we use whitespace to improve readability for humans.
  - Watch how I use whitespace and copy it.
- Next we declare some constants.
  - What constants you declare depends on the program you are writing.
    - Some might have many
    - Some might not have any.
  - Constants are values that will be the same for the entire program.
  - BUT we might want to change in some future version.
  - For our case, we will declare the two computer items to be constants.
  - ```
  ...
  using namespace std;
  
  const string COMPUTER_ITEM_1 = "blanket";
  const string COMPUTER_ITEM_2 = "jar of jam";
              
```
- The word const is called a reserved word.
  - This word has special meaning in c++
  - In this case, it means a value that will not change.
- string is a data type.
  - A string is a collection of 0 or more characters
  - A character is a fancy word for letter, but more...
  - We will discuss both of these in detail later.
- = is the assignment operator
  - It means copy what is on the right hand side of the = to the left hand side.
  - Draw this.
- Finally "blanket" and "jar of jam" are string literals
  - The values are literally stored in the code.
- Each of these lines are a statement, so they end with a semicolon ;.
- Finally we implement a main function.
  - ```
  ...
  const string COMPUTER_ITEM_2 = "jar of jam";
  
  int main() {
      cout << "The first computer item is " << COMPUTER_ITEM_1 << endl;
      cout << "The second computer item is " << COMPUTER_ITEM_2 << endl;
  
      return 0;
  }
```
- every program must have a main routine.
  - int is another data type.
  - It represents integers (1,2,3, ... 0, -1, -2, -3, ...)
  - We will discuss these more later.
- For now, just copy this line.
- There are three executable statements in the main function.
  - For now, cout represents the terminal, where we will write the output.
  - << is the stream insertion operator.
    - This sends whatever is next to the output.
  - "The first computer item is " is another string literal.
  - The program will get the value stored in COMPUTER_ITEM_1 and print it to the output.
  - endl prints a new line (enter key sort of)
  - We will discuss this in much more detail later.
  - return is a reserved word which means end the function that is currently executing.
Next we will transfer the code to a server and compile and execute it.