• The physical world is characterized by parameters such as
  • weight,
  • temperature,
  • pressure,
  • velocity,
  • flow,
  • and sound intensity and frequency.
  • Most physical parameters are continuous, typically capable of taking on all possible values over a defined range.
• the temperature, which is continuous, is measured by a sensor and converted to an electrical voltage, which is likewise continuous.We refer to such a continuous voltage as an analog signal, which is one possible way to represent temperature to an electrical voltage, which is likewise continuous.
• But, it is also possible to represent temperature by an electrical voltage that takes on discrete values that occupy only a finite number of values over a range, e.g., corresponding to integer degrees centigrade between -40 and +119. We refer to such a voltage as a digital signal.
  • Alternatively, we can represent the discrete values by multiple voltage signals, each taking on a discrete value. At the extreme, each signal can be viewed as having only two discrete values (0 or 1), with multiple signals representing a large number of discrete values.
  • temperature sensor is a AD convertor: a temperature at time that is then converted-to an anolog signal that is then coverted-to multi binay signals that is then coverted-to to multi binary digits
• Groups of bits, properly arranged, can even specify to the computer the program instructions to be executed and the data to be processed.
• Why is binary used?
  • consider a system with 10 values representing the decimal digits. In such a system, the voltages available—say, 0 to 1.0 volts—could be divided into 10 ranges, each of length 0.1 volt.This would require complex and costly electronic circuits, and the output still could be disturbed by small “noise” voltages or small variations in the circuits occurring during their manufacture or use.
    • As a consequence, the use of such multivalued circuits is very limited. Instead, binary circuits are used in which correct circuit operation can be achieved with significant variations in values of the two output voltages and the two input ranges. The resulting transistor circuit with an output that is either HIGH or LOW is simple, easy to design, and extremely reliable.
  • In addition, this use of binary values makes the results calculated repeatable in the sense that the same set of input values to a calculation always gives exactly the same set of outputs. This is not necessarily the case for multivalued or analog circuits, in which noise voltages and small variations due to manufacture or circuit aging can cause results to differ at different times.