3.1. What is "Embedded" and "Real-Time"?

"Embedded" and "real-time" can mean different things to different people, so let's define them as FreeRTOS uses them.

An embedded system is a computer system that is designed to do only a few things, like the system in a TV remote control, in-car GPS, digital watch, or pacemaker. Embedded systems are typically smaller and slower than general purpose computer systems, and are also usually less expensive. A typical low-end embedded system may have an 8-bit CPU running at 25MHz, a few KB of RAM, and maybe 32KB of flash memory. A higher-end embedded system may have a 32-bit CPU running at 750MHz, a GB of RAM, and multiple GB of flash memory.

Real-time systems are designed to do something within a certain amount of time; they guarantee that stuff happens when it's supposed to.

A pacemaker is an excellent example of a real-time embedded system. A pacemaker must contract the heart muscle at the right time to keep you alive; it can't be too busy to respond in time. Pacemakers and other real-time embedded systems are carefully designed to run their tasks on time, every time.