Single instruction computer $($SIC$)$ has only one instruction that can do all operations our RISC$-$V

does. The instruction has the following format

sbn a$,$ b$,$ c # Mem$[$a$]=$Mem$[$a$]-$ Mem$[$b$]$; if $($Mem$[$a$]<0)$ go to PC$+$c

For example, here is the program to copy a number from location a to location b:

Start: sbn temp, temp, $1$

sbn temp, a$,1$

sbn b$,$b$,1$

sbn b$,$ temp, $1$

Write a SIC program to add a and b$,$ leaving the result in a and leaving b unmodified.