By using pen and paper. I use to write all programs on paper, debug it by hand on paper. Then whenever I was confident that the programs I wrote will run withou

By using pen and paper. I use to write all programs on paper, debug it by hand on paper. Then whenever I was confident that the programs I wrote will run without errors, I use to go to a person's house who had a computer, pay him for 1hr access and run my programs. My parents could not afford to pay everyday, so every 1 or 2 week, I use to collect all my written programs and go type them as quickly as possible and try to compile and run them.