By having followed our programming proposal in the first three articles until now, you have all basic knowledge to approach the whole code you'll find in next page.
If you prefer to get the entire project, with form complete of Button and Memo, then download from here.
Unzip to get the project folder: inside you'll find some files.
You can run Lazarus and open from menu Project -> Open Project ... (Ctrl+F11), or double click on one of red bounded files shown in picture.
[unitmain form file will add the related text file to source editor too]
After that, all is ready for compilation: do it!
Here what you'll get:
And here the video: