The question is :

Consider a machine that perform calculation 4 bits a time. 8 bits 2's complement numbers can be added by adding the four least significant bits, followed by the four most significant bits. The leftmost bit is used for the sign, as usual. With 8 bits for each number, add -4 and -6, using 4 bit binary 2's complement arithmetic. Did over-flow occur ? Did carry occur ? Verify your numerical result.

Are supposed to write a program then?

If "yes" and in VB, then post the qustion in the VB forum