How many features must a Arduino uno has, before we call it perfect?

A number of people believe that the Arduino board is only a microcontroller, which is certainly inaccurate. In fact, the Arduino board is really a specially designed circuit board for programming and prototyping with Atmel microcontrollers.
The most important thing of the Arduino board is that it is not so much expensive and it is able to plug straight into a computer's USB port straightly, and it is very easy to set up and use. A lot of the key A good Arduino Uno generally contains some characters as bellow:

The first character of an Arduino Uno is designed with open source, only in this way can we use it to find someone to help us modify our projects easily.
Second, it can plug straightly into our USB ports and register with our computer system like a digital serial port. So, even though it is a serial device, we can also interface with it.
It must have a very convenient function of electrical power management and built-in voltage regulation. No matter whether you have an external power or not, it also can be charged anyway.
A cheap but good use microcontroller is necessary. The ATmega328 chip retails for about $2.88 on Yasurs. It has a great many of good hardware characteristics like timers, external and internal interrupts, and a number of sleep modes.
It will be a smart choice if it has a 16mhz clock. This would make it not the speediest microcontroller, but a very fast one.

It also has 13 digital pins and 6 analog pins, which allows you to connect external hardware to your Arduino. If you want to extend the computing capability of the Arduino into the real world, these pins are the first thing you should consider. And then, all you need to is plug your devices and sensors into the sockets that correspond to each of these pins.
The last but not least, it need a button to reset the program.