Build a digital calculator by usisng SystemVerilog to program the FPGA. calculator should handle two

$4$

$-$

bit binary values representing unsigned integers

$($

$0$

$-$

$1$

$5$

calculator should be capable of performing the following operations:

$$ Addition $(+)$

$$ Subtraction $(-)$

$$ The calculator should handle two $4-$bit binary values representing unsigned integers $(0-15).$

$2.$ Input and Output

$$ sw$[3$:$0]$ are used for inputting $4-$bit binary values.

$$ sw$4$ is used for the selecting operator $(1$ for addition and $0$ for subtraction$).$

$$ BTNL is used for resetting at any time.

$$ BTNU is used to confirm operand values.

$$ Seven$-$segment display is used to display values.

$$ BTND is used for changing the display mode.