# 041 what's happening: calling a method

When the computer runs your program, it reads one line of code at a time. It moves words and
numbers around in its memory. It is like moving sticky notes around on your desk.

Here is what one of the wheel lines you wrote in [L040](l040.md) does.

```java
hardware.frontLeft.setPower(leftSpeed);
```

:::{figure} ../_static/figures/fig-l040-sticky.png
:name: fig-l040-sticky
:::

- The computer finds the variable `hardware`, and the big blue note its arrow points to.
- On that note is the field `frontLeft`. Its arrow points to a motor's note.
- A motor has a method, `setPower`, and the line hands it `leftSpeed`. That is the `double` on
  `leftSpeed`'s note, 0.7 in the picture.
- `setPower` is part of the FTC platform. It runs that motor full power forward at +1.0, not at
  all at 0.0, and full power backward at -1.0.
- The same happens for each of the four: `frontLeft`, `backLeft`, `frontRight` and `backRight`.