;calculates the result of squaring the number. example :
;10 squared = sum of adding 10, ten times.

BR main

num:    .word 0
val:    .word 0
res:    .word 0
msg1:   .ascii "Number: \x00"
msg2:   .ascii " is invalid \x00"
msg3:   .ascii " Squared = \x00"


checkVal: LDA 2,s
          CPA 0,i ;checks if number > 0
          brgt valid
          LDA 0,i ; puts 0 in the return value(to be interpreted as 'false')
          STA 4,s
          RET0
valid:    LDA 1,i ; puts 1 in the return value(to be interpreted as 'true')
          STA 4,s
          RET0


sqNum: SUBSP 4,i ; 2 local variables
       LDA 0,i
       STA 2,s
while: LDA 2,s ;squares the number
       CPA 6,s
       BRGE out
       LDA 2,s
       ADDA 1,i
       STA  2,s
       LDA 0,s
       ADDA 6,s
       STA 0,s
       BR while
out:   LDA 0,s ; done calculating the result
       STA 8,s ; save result in return value.
       ADDSP 4,i
       RET0

main: DECI num,d
      SUBSP 2,i ; return value
      SUBSP 2,i ; parameter
      LDA   num,d
      STA   0,s
      CALL checkVal
      ADDSP 2,i ; parameters go away
      LDA   0,s
      STA  val,d
      ADDSP 2,i   ;clear return value
      LDA  val,d
      brgt cont
      STRO msg1,d
      DECO num,d
      STRO msg2,d
      BR  done

cont: SUBSP 2,i ; return value
      SUBSP 2,i ;parameter
      LDA num,d
      STA   0,s
      CALL sqNum
      ADDSP 2,i ; clear parameter
      LDA   0,s
      STA   res,d
      ADDSP 2,i ; clear return value
      STRO  msg1,d
      DECO  num,d
      STRO  msg3,d
      DECO  res,d

done: STOP
.end