LC-3 で電卓を作成する Web サイトで見つけた問題に取り組んでいます。私はそれを段階的に進めており、スタックを使用して現在行っていることについて何かを見ました。これまでのところ、スタックを使用するように変換するために誰かが私を助けることができるかどうか疑問に思っていました.これまでのところ、私はレジスタを使用しています! 以下のコードは明らかに不完全です。これは、いくつかのことを行う方法について調査を停止して開始したときに得たものです。私がこれまでに持っていたもののLC-3コードは次のとおりです。
;get first string from user
START LEA R0, PROMPT1 ; Display the prompt
PUTS
LEA R0, BUFFER
JSR READLINE
;convert string to number
LEA R0, BUFFER
JSR ATOI
;save the number
ST R0, FIRST_ARG
;get second string from user
LEA R0, PROMPT2 ; Display the prompt
PUTS
LEA R0, BUFFER
JSR READLINE
;convert string to number
LEA R0, BUFFER
JSR ATOI
;save the number
ST R0, SECOND_ARG
;load the arguments into R0 and R1
LD R0, FIRST_ARG
LD R1, SECOND_ARG
JSR SUM
PRINT_OUTPUT
;convert R0 into a string
LEA R1, BUFFER
JSR ITOA ;not made yet, also will need division and subtraction subroutines
;print the sum of the two digits entered
LEA R0, ANSWER ; Display the prompt
PUTS
LEA R0, BUFFER
PUTS
;print a new line character.
LD R0, ENTER
OUT
STOP HALT ;
;subroutine SUM : calculates the sum of two numbers
;input: R0,R1
;output: R0 = R0 + R1
SUM
ADD R0, R0, R1
RET
;subroutine PROD : calculates the product of two numbers
;input: R0,R1
;output: R0 = R0 * R1
MUL
ST R2, MUL_SAVE_R2
AND R2, R2, #0
AND R1, R1, R1
MUL_START
BRz MUL_END
ADD R2, R2, R0
ADD R1, R1, #-1
BR MUL_START
MUL_END
ADD R0, R2, #0
LD R2, MUL_SAVE_R2
RET
MUL_SAVE_R2 .FILL x0000
;subroutine READLINE : Reads a line of input from keyboard.
;input: R0. contains the address of the memory location where the
; string must be placed.
READLINE
ST R7, RL_RETURN
AND R1, R0, R0
RL_START
;get a character and echo it
GETC
OUT
;compare the character with ENTER which has ascii value 10
ADD R2, R0, #-10
BRz RL_END ;the user typed ENTER, stop the loop
STR R0, R1, #0 ;store whatever the user typed
ADD R1, R1, #1 ;increment the pointer
BR RL_START
RL_END
AND R0, R0, #0
STR R0, R1, #0 ;write the null character
LD R7, RL_RETURN
RET
RL_RETURN .FILL x0000
;subroutine ATOI : Converts an ASCII string to an integer
;input: R0, contains the address of the string
;output: R0, should contain the integer value
ATOI
ST R7, ATOI_RETURN
AND R2, R0, R0 ;R2 <- R0;
AND R0, R0, #0 ;R0 <- 0
ADD R1, R0, #10 ;R1 <- 10
LD R4, ASCIIZERO
NOT R4, R4
ADD R4, R4, #1 ;This is to convert ascii character to integer
ATOI_START
LDR R5, R2, #0
BRz ATOI_END ;we've reached the end of the string
AND R1, R1, #0
ADD R1, R1, #10 ;R1 <- 10
JSR MUL ;multiply current number by 10
ADD R5, R5, R4 ;subtract ASCIIZERO from R5
BRn INVALID_INPUT ;user typed something less than '0'
ADD R6, R5, #-9
BRp INVALID_INPUT ;user typed something more than '9'
ADD R0, R0, R5
ADD R2, R2, #1 ;next character
BR ATOI_START
INVALID_INPUT
AND R0, R0, #0 ;make R0 <- -1
ADD R0, R0, #-1
ATOI_END
LD R7, ATOI_RETURN
RET
ATOI_RETURN .FILL x0000
;allocate memory for the input
FIRST_ARG .FILL x0000
SECOND_ARG .FILL x0000
BUFFER .BLKW #15 ; allocating memory for storing user input.
POP
LDR R0, R6, #0
ADD R6, R6, #1
RET
PUSH
ADD R6, R6, #-1
STR R0, R6, #0
RET
;constants
MINUS .FILL x002D; '-'
ENTER .FILL x000A; newline character
PROMPT1 .STRINGZ "Please input the first digit > "
PROMPT2 .STRINGZ "Please input the second digit > "
ANSWER .STRINGZ "Sum of the two digits entered = "
ASCIIZERO .FILL x0030; '0'
.END