Practical programming of AVR microcontrollers, including the popular Arduino platform, is considered. It tells how to go beyond the limitations of Arduino, when to use direct assembly programming, and when to use high-level languages. General principles of AVR microcontrollers and their programming, command system, timer programming, arithmetic operations, memory, interfaces, power saving modes and a watchdog timer, real-time programs, data exchange with a personal computer are described. Particular attention is paid to the transfer of typical Arduino projects to assembler. Ready-made recipes are given for programming most of the main functions of modern microelectronic equipment.