I have mice looking and walking in my game, but they are very slow and hard to use. I think it's because I'm using fixed speed. I heard that in big projects developers use delta time. How do I calculate delta time in glut? How do I calculate speed using delta time?
The "delta time" used to be the time elapsed between two frame updates (but it can also be used in other contexts; this is usually the result of a time subtraction).
You can get the delta time in glut using the glutGet method and the GLUT_ELAPSED_TIME parameter, plus some operations.
So if you register the current timeSinceStart at each rendering loop, you can know the deltaTime by subtracting the old one to the new one.
Basically, you can use deltaTime to update your movements in ratio to this elapsed time instead of using a fixed time value. This way, the movement speed of your character should be almost the same if your program runs at 60 fps or if it runs at 10 fps.
This way, whether your program updated 2 times or 100 times, 1 second later the position should be almost the same, and the game-play is less impacted by the low fps of a small computer than if it use fixed values.
Finally, you should read Fixed time step vs Variable time step on gamedev.stackexchange.