There are some fundamental concepts related to embedded application development.

• Real-Time: some embedded applications must receive continuous inputs, processing them, and generate outputs of data, where such processing must be performed in a very short period of time. As an example, some applications demand object detection in live stream videos, where processing involves inference and bounding boxes with labels displayed on each frame. This process must be performed as fast as possible.

• Fault-Tolerance: this is the capability of an embedded system to survive in the presence of faults. Faults can be caused by power cuts, hardware damaged parts, overwarming, and more. The embedded software must be capable of detecting faults and make decisions according to how critical a fault is. As an example, an embedded system working inside an airplane must be capable of identifying any possible fault and make decisions in order to keep the aircrew safe. Decisions can be as simple as sending an alert or as complex as performing changes in the command control.

• Portability: this is the measure of how easy it is to use the same embedded software in multiple environments. It requires generalized abstractions between the application program logic and the low-level system interfaces. As an example, embedded devices used in domotic applications must be adjustable no matter the place where they have to be installed.

• Reliability: this is the survival probability of the system when the function is critical during the run time. As an example, embedded systems used in self-driven cars must be able to make decisions in runtime, where many tasks are critical to keep passengers and pedestrians safe. In this case, reliability must be as high as possible.

• Flexibility: an embedded system must be built with built-in debugging opportunities, allowing remote maintenance. For example, embedded systems in a satellite which must collect various types of data and send it back to a central station. If at some point the satellite loses control, people from the station should be able to make a diagnosis trying to reestablish the system. That is why flexibility is vital while designing an embedded system.

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Embedded systems take action depending on the environment they interact, by using sensors that take in data from the environment and produce an output that can be processed or can be the same as they were able to capture.

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Embedded application development can have multiple applications as targets. Embedded systems can be classified as follows:

• Embedded systems based on performance and functional requirements

  • Real-time embedded systems.
    These embedded systems provide an output in a particular/defined time interval. This type of embedded systems produce quick responses under critical situations by giving high priority to time based task performance and the generation of output.

    • Soft real-time embedded systems.
      In these embedded systems the deadlines for tasks are not followed strictly. There is an acceptable threshold.​

    • Hard real-time embedded systems.
      In these embedded systems the deadlines for tasks are followed strictly.

    • Examples:

      • Medical appliances​

      • Traffic control systems

      • Security systems

  • Stand alone embedded systems:
    These embedded systems are independent systems that can work by themselves without host system dependency.​​

    • Examples:​

      • Calculators​

      • Microwave ovens

      • MP3 players

  • Networked embedded systems:
    Those are embedded systems connected to a wired/wireless network to provide outputs to the attached devices. These embedded systems are able to communicate with embedded web servers through the network.​​

    • Examples:​

      • Card swipe machines​

      • Domotic systems

  • Mobile embedded systems:
    These are small embedded systems which generally require less resources. They are considered the best in terms of portability.​​

    • Examples​

      • Digital cameras​

      • Cellphones

      • Smartwatches

• Embedded systems based on performance and micro-controller:​​​

  • Small scale embedded systems:
    These are embedded systems designed by using an 8-bit or 16-bit microcontroller which can be powered with a battery. They use limited resources of memory and processing. Generally, these systems act as a component of a bigger computing system.​

    • Examples:​

      • Washing machine​

      • Small digital cameras

  • Medium scale embedded systems:​​
    Those are embedded systems designed by using a 16-bit or 32-bit micro-controller, being faster than the small scale embedded systems. The integration process of hardware and software is complex in these systems. Different types of software tools like compilers, debuggers, and simulators are part of the embedded software development.

    • Examples:​

      • Routers for networking​

      • ATM machines

  • Complex embedded systems:
    These embedded systems are designed by using multiple 32-bit or 64-bit micro-controllers. Compex embedded systems are developed to perform large scale sophisticated functions having high hardware and software complexities. The systems also use Real-Time Operating Systems (RTOS) and complicated time bound applications. Hardware and software components are used in the final design of systems or hardware products.

    • Examples:​

      • Smartphones, tablets, and laptops​

      • Multimedia systems