Generally we are listing two words like Microprocessor and Microcontroller in this digital world. Today’s world completely depended on microprocessors and microcontrollers. So we have to know about microprocessor microcontroller. First what is a microprocessor? A Microprocessor is a digital integrated circuit which is used in general computer and having the millions of transistors, resistors and other electronic components incorporate in as single small IC.  The microprocessor is works as CPU (central processing unit) of the computer. The microprocessor is designed to support a set of multiple peripheral like USB ports, video ports, audio ports, network interfaces like Ethernet, WI-Fi, Bluetooth, additional memory interfaces like CD/DVD ROM, magnetic disc drives and SD/MMC external interfaces. 

AVR microcontrollers are the advanced microcontrollers.Mainly the AVR family is sub grouped as ATmega, ATtiny, Xmega, UC3, SAM3 and SAM4. In these form 8 to 32 bit controllers are available. All the controllers having some common and some different features, those are coming to common features all are having I/O ports, timer/counters, interrupts and etc, coming to special features those are A/D converters, PWM, D/A converter, on chip I2C, serial communication interfacings, on chip EEPROM and etc. we can use all these features according to our requirement by programming. First we have to discuss about I/O ports. Generally, AVR microcontrollers having four I/O ports named as PORTA, PORTB, PORTC, PORTD. Take example as ATMEGA8 or ATMEGA 16 or ATMEGA32 microcontrollers, these are any having four I/O ports and each port having 8 I/O lines and totally each controller having 32 I/O lines.  

 Generally we are listening the wards PCB’s, PCB layout, PCB designing, ect. But what is PCB? Why we are using this PCB? We want to know about all these things as a electronic engineer. PCB means Printed Circuit Board. This is a circuit board with printed copper layout connections. These PCB’s are two types. One is dotted PCB and another one is layout PCB. What is the main difference between the dotted PCB and layout PCB? In dotted PCB board only dots are available. According to our requirement we can place or insert the components in those holes and attach the components with wires and soldering lid. In this dotted PCB we can make the circuit as out wish but it is very hard to design. There are so many difficulties are there. Those are connecting the proper pins, avoiding shot connections and etc. Coming to the layout PCB this is simple to design.