• collection of some bits (8 bits in case of 8bit MCUs).
• Either each different bit in a register has some purpose or the register as a holds a value.
• Registers works as connection between a CPU and a Peripheral device (like ADC or TIMER).
• By changing the value of the register the CPU is actually instructing the PERIPHERAL to do something or it is configuring it in some way.
• And by reading a register,The CPU can know the state of peripheral or read associated data.

• configure and command the peripheral

• transfer the data

• Get the status and data from peripheral

Most of the time we are not interested in the value of the variable but the state of the register .

// if we declare a variable to store the state of register eg

// int reg = 10101010;

// compiler takes 10101010 as decimal no

// we have to do this like int reg = 0b101010101 and reg= 0x10101010

ob for binary ox for hexadecimal