Write a program for the UART interface

Remote work for a programmer. You need to write a program for the UART interface. The program for the MK should perform the following actions:
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1. Store in MK RAM (in uint8 variables)
{a, b, c, d, e} After the launch of the MK before entering new values in
The quality of the variable values is set to zero;
2. Provide a constant display of the value of one of the
Variables on four seven-segment indicators in the form of
“.”, e.g. “a.123”;
3. Performing the processing of external interruptions:
3.1. When the INT0 interrupt is triggered, proceed to the conclusion
The following (cyclically: a→b→c→d→e→a→...) variable on
The seven-segment indicator;
3.2. When the INT1 interrupt is triggered, transmit
The value of the variable currently displayed
Seven-segment indicator, in the PC terminal (UART interface) in the form of "=",
For example, "a=123."
4. Perform the following commands coming over the UART interface from the PC terminal (for reading commands you need to be able to use the computer).
Use the UART_RXC interrupt:
4.1. Enter new values for variables. Input format:
“=”, for example, “a=123”;
4.2. Performing arithmetic operations {+, -, *} with
Variables {a, b, c, d, e}. In response, the MK sends the result
Operations. Input format:
"=,"
For example, "=a+b";

UART-interface settings: speed 4800 baht, control
Even parity, two stop bits, 8 significant bits in a packet.