Dr. Irfan Zafar
Digital means anything which has to do with digits, but in today's world digital means CMOS (complementary metal
oxide semiconductor), TTL gates, flip-flops, processors, computers.
The quantities that are to be measured, monitored, recorded, processed and controlled are analog and digital,
depending on the type of system used. It is important when dealing with various quantities that we be able to
represent their values efficiently and accurately. There are basically two ways of representing the numerical value of
quantities: analog and digital.
Systems which are capable of processing a continuous range of values varying with respect to time are called analog
systems. In analog representation a quantity is represented by a voltage, current, or meter movement that is
proportional to the value of that quantity. Analog quantities such as those cited above have an important
characteristic: they can vary over a continuous range of values.
Diagram of analog voltage vs time
Systems which process discrete values are called digital systems. In digital representation the quantities are
represented not by proportional quantities but by symbols called digits. As an example, consider the digital watch,
which provides the time of the day in the form of decimal digits representing hours and minutes (and sometimes
seconds). As we know, time of day changes continuously, but the digital watch reading does not change
continuously; rather, it changes in steps of one per minute (or per second). In other words, time of
day digital representation changes in discrete steps, as compared to the representation of time
provided by an analog watch, where the dial reading changes continuously.
Below is a diagram of digital voltage vs time: here input voltage changes from +4 Volts to -4 Volts;
it can be converted to digital form by A