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Text File  |  1996-12-24  |  2KB  |  56 lines
  1. ******************************
  2. *    OVRLY  11/13/88         *
  3. *    COPYRIGHT 1988          *
  4. *    BY E. L. CRANFORD, JR.  *
  5. *    ST. PETERSBURG, FL      *
  6. ******************************
  7.  
  8. START     = $300
  9.           ORG START
  10. CHRGET    = $B1
  11. CHKCOM    = $DEBE
  12. FNDLIN    = $D61A
  13. LOWTR     = $9B
  14. LINGET    = $DA0C
  15. TEXTTAB   = $67
  16. TEXTTMP   = $1E
  17. STORE     = $A8
  18. RECALL    = $A7
  19. *-------------------------------
  20.           LDA #EVAL      ;Set & vector.
  21.           STA $3F6
  22.           LDA #>EVAL
  23.           STA $3F7
  24.           RTS
  25. *-------------------------------
  26. EVAL      PHA            ;Save token.
  27.           JSR CHRGET     ;Advance TXTPNTR.
  28.           PLA            ;Recover token.
  29.           CMP #STORE
  30.           BEQ MOVSTART
  31.           CMP #RECALL
  32.           BEQ RESET
  33.           RTS            ;Missed.
  34. *---------------------------
  35. MOVSTART  LDA TEXTTAB    ;Save original program
  36.           STA TEXTTMP    ;start pointer.
  37.           LDA TEXTTAB+1
  38.           STA TEXTTMP+1
  39.           JSR CHKCOM     ;Check for a  comma
  40.           JSR LINGET     ;Find the line which will
  41.           JSR FNDLIN     ;be the last line in the
  42.           LDY #0         ;main program.
  43.           LDA (LOWTR),Y  ;Find the location for the
  44.           STA TEXTTAB    ;beginning of the overlay
  45.           INY
  46.           LDA (LOWTR),Y  ;and set program start
  47.           STA TEXTTAB+1  ;pointer.
  48.           RTS
  49. *-------------------------------
  50. RESET     LDA TEXTTMP    ;Reset program start to
  51.           STA TEXTTAB    ;original location.
  52.           LDA TEXTTMP+1
  53.           STA TEXTTAB+1
  54.           RTS
  55. *-------------------------------
  56.