C   P R O G R A M   ( f i r s t _ p r o g . c ) :
#include <stdio.h>

int main()
{
  int A = 3;
  int B = 5;
  int C;

  C = A + B;

}



C O M P I L E D   P R O G R A M   ( f i r s t _ p r o g . a s m ) :
.Orig x3000	; R7 saved PC,   R6 StkPtr,  R5 FramePtr,   R4 GlobalStkPtr
INIT_CODE
LEA R6, #-1		; set StkPtr = xEFFF
ADD R5, R6, #0
ADD R6, R6, R6
ADD R6, R6, R6
ADD R6, R6, R5
ADD R6, R6, #-1
ADD R5, R5, R5		; ? (oops! "no harm" error)
ADD R5, R6, #0		; set FramePtr = xEFFF
LD R4, GLOBAL_DATA_POINTER  ; set GlobalStkPtr = "GLOBAL_DATA_START"
LD R7, GLOBAL_MAIN_POINTER  ; load R7 with address of "main"
jsrr R7			; begin "main"
HALT

GLOBAL_DATA_POINTER .FILL GLOBAL_DATA_START
GLOBAL_MAIN_POINTER .FILL main
;;;;;;;;;;;;;;;;;;;;;;;;;;;;main;;;;;;;;;;;;;;;;;;;;;;;;;;;;
main
ADD R6, R6, #-2		; PUSH space for return value
STR R7, R6, #0		; PUSH R7 (addr of HALT)
ADD R6, R6, #-1		; PUSH FramePtr
STR R5, R6, #0
ADD R5, R6, #-1		; create new FramePtr

ADD R6, R6, #-3		; PUSH space for 3 local variables (A, B, & C)
ADD R7, R4, #5		; get A=3 (L2) from GlobalStkPtr+5, str at FramePtr-0
ldr R7, R7, #0
str R7, R5, #0
ADD R7, R4, #4		; get B=5 (L3) from GlobalStkPtr+4, str at FramePtr-1
ldr R7, R7, #0
str R7, R5, #-1
ldr R7, R5, #0		; A+B and str into FramePtr-2
ldr R3, R5, #-1
add R7, R7, R3
str R7, R5, #-2
ADD R7, R4, #3		; get (L4=0) from GlobalStkPtr+3,  
ldr R7, R7, #0		;	str at FramePtr+3 (return value space)
lc3_L1_first_prog
STR R7, R5, #3
ADD R6, R5, #1		; POP local variables (A,B,C)
LDR R5, R6, #0		; POP last FramePtr
ADD R6, R6, #1
LDR R7, R6, #0		; POP last R7 (Addr of HALT)
ADD R6, R6, #1
RET			; return to HALT


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;	void scanf(const char *format, ...) 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; 

SCANF_PERCENT .FILL -37
SCANF_C .FILL -99
SCANF_D .FILL -100
SCANF_S .FILL -115 
SCANF_0 .FILL -48 
SCANF_9 .FILL -57  
SCANF_MINUS .FILL -45  
SCANF_BUF .BLKW 6
 
lc3_scanf 
  ...			; remainder of code for scanf not included
 
 
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;	void printf(const char *format, ...)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

PRINTF_PERCENT .FILL -37
PRINTF_C .FILL -99
PRINTF_D .FILL -100
PRINTF_S .FILL -115
PRINTF_B .FILL -98
PRINTF_O .FILL -111
PRINTF_X .FILL -120
PRINTF_ASCII .FILL 48 		;postive ascii value of '0'
.FILL 49
.FILL 50
.FILL 51
.FILL 52
.FILL 53
.FILL 54
.FILL 55
.FILL 56
.FILL 57
.FILL 65        ;A
.FILL 66
.FILL 67
.FILL 68
.FILL 69
.FILL 70
PRINTF_MINUS .FILL 45  
PRINTF_BUF .BLKW 18
 
lc3_printf
  ...			; remainder of code for printf not included



GLOBAL_DATA_START	
L1_first_prog .FILL lc3_L1_first_prog  ; <- GlobalStkPtr (follows all code)
scanf .FILL lc3_scanf
printf .FILL lc3_printf
L4_first_prog .FILL #0
L3_first_prog .FILL #5
L2_first_prog .FILL #3
.END



S T A C K   S N A P S H O T S :

Stk before main: 
xEFFC  
xEFFD 
xEFFE
xEFFF				<- StkPtr <- FramePtr (initially)


Stk at main  :
xEFF6
xEFF7
xEFF8
xEFF9
xEFFA
xEFFB 				<- FramePtr (main)
xEFFC  R5 FramePtr (xEFFF)
xEFFD  R7 Saved PC (x300B)
xEFFE  return value from main space
xEFFF				<- StkPtr <- FramePtr (initially)


Stk before "C = A + B" in main:
xEFF6
xEFF7
xEFF8
xEFF9   C = ?
xEFFA   B = 5
xEFFB   A = 3(main local var)	<- FramePtr (main)
xEFFC  R5 FramePtr (xEFFF)
xEFFD  R7 Saved PC (x300B)
xEFFE  return value from main space
xEFFF				<- StkPtr <- FramePtr (initially)


Stk after "C = A + B" in main :
xEFF6
xEFF7
xEFF8
xEFF9   C = 8
xEFFA   B = 5
xEFFB   A = 3(main local var)	<- FramePtr (main)
xEFFC  R5 FramePtr (xEFFF)
xEFFD  R7 Saved PC (x300B)
xEFFE  return value from main space
xEFFF				<- StkPtr <- FramePtr (initially)


Stk before RET to HALT :
xEFFB
xEFFC
xEFFD
xEFFE  return value from main space
xEFFF				<- StkPtr <- FramePtr (initially)