ADD examples:

Direct
Indirect
     SETPCSTART 20
     ORG 20
     LDA VALA
     ADD VALB
     STA VALC
     HLT

VALA HEX 25
VALB HEX 31
VALC HEX 0

     SETPCSTART 20
     ORG 20
     LDA LOCA I
     ADD LOCB I
     STA LOCC I
     HLT

LOCA HEX VALA
LOCB HEX VALB
LOCC HEX VALC

VALA HEX 72
VALB HEX 24
VALC HEX 0
Result is VALC gets 56
Result is VALC get 96