$?210($decremented by $1$ each time the loop is executed$)$

DAT $,0$

Assume now that the above program will only read $3$ numbers. That is$,$ the following numbers in

this order will be placed, one at a time, in the In$-$basket: $2,18,$ and $15,$ where $2$ is the count of

numbers that follow, and $18$ and $15$ are the numbers that are to be added. The first column in the

table on page $4$ shows the order in which the instructions from the program will be executed. Trace

the execution of these instructions and determine the contents of the PC before and after each

instruction is executed. Also, write down in the table the contents of the In$-$basket; Accumulator;

Memory locations $25,26,$ and $27$; and Out$-$basket after each instruction is executed. Memory

location $25$ controls the loop. It initially contains an unknown value $(?),$ then $2,$ next $1,$ and finally $0.$

Memory location $26$ always contains $1.$ It is used to decrease the loop count by $1.$ Memory location

$27$ is initialized with $0,$ and finally it stores $33,$ the sum of $18$ and $15.$ The entry $1011$ in the PC

column means that the PC is $10$ when the instruction IN started and is changed to $11$ when the

instruction IN is finished.