The Universal System Model

All things that perform a function can be described with the Universal Systems Model. There are four basic elements that define this model:

1. Input
2. Process,
3. Output
4. Feedback

For example, a car: The goal of a car is to move or go forward (or backward). To use the Universal System Model to describe this function would be as follows:

1. Input - step on the gas, the car takes in gas
2. Process - the cylinders burn the fuel which makes the wheels turn (intake/compression/combustion/exhaust)
3. Output - the car moves forward (or backward)
4. Feedback - the speedometer shows the speed at which the car is moving

Another example, a blender: The goal of a blender is to produce a mixture - usually a drink or smoothie. To use the Universal System Model to describe this function would be as follows:

1. Input - put in the bananas, milk, chocolate, berries, etc.
2. Process - blend
3. Output - the smoothie
4. Feedback - taste

A computer USM would be as follows:

1. Input - A user presses the letter A on the keyboard or clicks a mouse
2. Process - the Central Processing Unit (CPU) processes the instructions
3. Output - the monitor or printer displays the A
4. Feedback - the data - the letter A

In a computer, the process of getting the information from the keyboard to the Central Processing Unit (CPU) to be processed and then to the monitor to be displayed involves a critical component called the BUS and a signal called an IRQ.

When a user hits the letter A on the keyboard, an electronic signal is generated in the form of ASCII Code - a predetermined set of 1's and 0's (called binary bits). Although computers "talk" in binary, human's writing the code, or programming the applications that run on a computer, use hexadecimal. This signal or message has to travel from the keyboard to the CPU by way of the BUS - a physical electronic path. Before the keyboard sends the signal, it generates an interrupt request (IRQ) to alert the system it has a message. All components have a specific IRQ and they are not arbitrary - they are predetermined and agreed upon by all manufactures so conflicts should not arise. After the IRQ is generated, the message is delivered to the CPU for processing via the bus. The CPU processes the message and determines it is to be displayed on the monitor. The CPU must then generate an IRQ to alert the system it has a message. Once generated, the message is delivered to the monitor via the bus.

There are many more elements involved as well: Memory (RAM & ROM), Storage, Operating System (OS), and Application Software, just to name a few. What is described above is just the basic overall picture of the computer logic.

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