This book is a collection of examples of C programs for ATMEL microcontrollers. The WinAVR compiler, AVR Studio environment and Proteus ISIS schema simulator were used as development and simulation tools. The syntactic features of the C language and methods of working with the tools listed above are not considered in detail in the book, since the author aimed to give the maximum number of practical examples of using certain peripheral devices of the microcontroller: timer counters, U (S) ART transceiver, analog comparator, ADC, SPI and TWI interfaces, Flash memory and EEPROM A separate chapter is devoted to interaction with the LCD module. Thus, this publication is designed for those readers who, possessing basic knowledge of the C language, want to learn how to use them in working with ATMEL microcontrollers.