At some point, you have to jump out of the plane under the assumption that you can get the parachute sewn together in time to deploy it.
We usually write programs that operate one step at a time, in a sequence. In the following picture, the value of a bank balance is fetched, it is increased by the value of the deposit, and then it is copied back into the account record:
Real bank tellers and computer programs go through similar sequences. In a computer, a sequence of steps executed one at a time is called a thread. This single-threaded programming model is the one most programmers use.
In a real bank, more than ...