The small program described here is known as a program loader, or$,$ under certain circumstances as a bootstrap. This

program takes advantage that instructions and data are indistinguishable. Thus, instructions could be treated as if they

were data, if necessary.

Mailbox Mnemonic Opcode Comment

$86$ LDA $98598//$ initialize the STORE instruction at loc. $92$

$87$ STO $92392//$ storing the contents of mailbox $98,$ that is $301$

$88$ INP $901//$ input a value

$89$ SUB $97297//$ subtract $999$

$90$ BRZ $01701//$ done loading$--$jump to $01$ for execution

$91$ ADD $97197//$ restore input value

$92$ DAT $00//$ store value. This will contain $3$XX$,$ with XX indexed

$93$ LDA $92592//$ load the STORE instruction in $92$

$94$ ADD $99199//$ increment it

$95$ STO $92392//$ and resave it

$96$ BRA $88688//$ continue with the next input

$97$ DAT $999999//$ value $999$ for testing

$98$ DAT $301301//$ initial STORE $01$ instruction as a data value

$99$ DAT $011//$ value $1$ for indexing

II$.-$ What you need to do

$1.$ Load the above program loader in the LMC to understand what the program is doing. The instructions

should be loaded in your LMC at the mailboxes indicated above to work properly. Ensure that in mailbox $00$

you have the instruction to branch to mailbox $86($first instruction of the program loader$).$

$2.$ Run the program loader and input the instructions of the following user program:

$//$ Input three numbers, output the sum of the first two, and output the third minus the first

$00$ INP

$01$ STA $09$

$02$ INP

$03$ ADD $09$

$04$ OUT

$05$ INP

$06$ SUB $09$

$07$ OUT

$08$ HLT

$09$ DAT $00$

Hint: Replace the mnemonics with the opcodes to input the instructions of this user program as numbers.

$3.$ Move the program loader so that it starts at mailbox $00$ in the LMC$.$ Modify as required so it works

properly.

a$.$ You need to take in consideration the relative positioning of the mailboxes and branches and modify

as required so it works properly

b$.$ The original program loader loads the user program starting at mailbox $01,$ you need to change this

to load the user program starting at mailbox $30.$