Starting point for PS6 Question #3.

calc_v2_starter.asm

;
; calc_v2.asm
; Performs addition/subtraction/multiplication/division/modulus/exponentiation
; between 2 single-digit, user-entered values to produce 1-2 digit result.
;

; R5 - operation type
; R4 - operand 1
; R3 - operand 2

.ORIG x3000

        ; retrieve operand 1 value from user - convert to integer value
        GETC            ; retrieve character entered
        OUT             ; echo it back to user
        ADD R4, R0, #0  ; move value from R0 to R4
        LD R1, ZERO     ; load ASCII Base for zero
        NOT R1, R1
        ADD R1, R1, #1  ; negate ASCII base
        ADD R4, R4, R1  ; add negated base to produce numerical value
        ; output a space
        LD R0, SP       ; load a Space
        OUT             ; output a Space
        ; retrieve operation
        GETC            ; retrieve character entered
        OUT             ; echo it back to user
        ADD R5, R0, #0  ; move value from R0 to R5
        ; output a space
        LD R0, SP       ; load a Space
        OUT             ; output a Space
        ; retrieve operand value from user - convert to integer value
        GETC            ; retrieve character entered
        OUT             ; echo it back to user
        ADD R3, R0, #0  ; move value from R0 to R3
        ADD R3, R3, R1  ; add negated base to produce numerical value
        ; output a space
        LD R0, SP       ; load a Space
        OUT             ; output a Space

        ; check operation types
        ; check for subtraction
        LD R6, MINUS
        NOT R6, R6,
        ADD R6, R6, #1  ; negate
        ADD R6, R5, R6  ; subtract to compare
        BRz SUBIT
        ; check for addition
        LD R6, PLUS
        NOT R6, R6,
        ADD R6, R6, #1  ; negate
        ADD R6, R5, R6  ; subtract to compare
        BRz ADDIT
        ; check for multiply
        LD R6, STAR
        NOT R6, R6,
        ADD R6, R6, #1  ; negate
        ADD R6, R5, R6  ; subtract to compare
        BRz MULIT
        ; check for divide
        LD R6, SLASH
        NOT R6, R6,
        ADD R6, R6, #1  ; negate
        ADD R6, R5, R6  ; subtract to compare
        BRz DIVIT
        ; check for modulo
        LD R6, PERC
        NOT R6, R6,
        ADD R6, R6, #1  ; negate
        ADD R6, R5, R6  ; subtract to compare
        BRz MODIT
        ; check for exponentiation
        LD R6, POW
        NOT R6, R6,
        ADD R6, R6, #1  ; negate
        ADD R6, R5, R6  ; subtract to compare
        BRz EXPIT

ADDIT   JSR ADDITION
        BRnzp END

SUBIT   JSR SUBTRACT
        BRnzp END

MULIT   JSR MULTIPLY
        BRnzp END

DIVIT   JSR DIVIDE
        BRnzp END

MODIT   JSR MODULUS
        BRnzp END

EXPIT   JSR EXPONENT
        BRnzp END

END     JSR INT2CHR
        HALT

; --------------------------- ADDITION SUBROUTINE ---------------------------- ;
; Description: performs addition between two values - R1 = R4 + R3
; Inputs: R4 - value 1, R3 - value 2
; Outputs: R1 - sum
ADDITION
        RET

; ------------------------- SUBTRACTION SUBROUTINE -------------------------- ;
; Description: performs subtraction between two values - R1 = R4 - R3
; Inputs: R4 - minuend, R3 - subtrahend
; Outputs: R1 - difference
SUBTRACT
        RET

; ------------------------ MULTIPLICATION SUBROUTINE ------------------------- ;
; Description: performs multiplication between two values - R1 = R4 * R3
; Inputs: R4 - factor 1, R3 - factor 2
; Outputs: R1 - product
MULTIPLY
        RET

; --------------------------- DIVISION SUBROUTINE ---------------------------- ;
; Description: performs division between two values - R1 = R4 / R3
; Inputs: R4 - dividend, R3 - divisor
; Outputs: R1 - quotient
DIVIDE  RET

; --------------------------- MODULUS SUBROUTINE ---------------------------- ;
; Description: performs modulus between two values - R1 = R4 % R3
; Inputs: R4 - dividend, R3 - divisor
; Outputs: R1 - remainder
MODULUS
        RET

; ------------------------ EXPONENTIATION SUBROUTINE ------------------------- ;
; Description: performs exponentiation between two values - R1 = R4 ^ R3
; Inputs: R4 - value 1, R3 - value 2
; Outputs: R1 - result
EXPONENT
        RET

; ----------------------- INTEGER TO ASCII SUBROUTINE ------------------------ ;
; Description: converts 1-2 digit integer to ASCII char and prints to console.
; Input: R1 - integer value to convert
; Output: No registers. Prints resulting ASCII characters to console.
INT2CHR
        RET



; ----------------------- RAW VALUES STORED IN MEMORY ------------------------ ;
EQUALS  .FILL x003D     ; ASCII representation of an equals sign '='
PLUS    .FILL x002B     ; ASCII representation of a plus sign '+'
MINUS   .FILL x002D     ; ASCII representation of a minus sign '-'
STAR    .FILL x002A     ; ASCII representation of a minus sign '*'
SLASH   .FILL x002F     ; ASCII representation of a minus sign '/'
PERC    .FILL x0025     ; ASCII representation of a minus sign '%'
POW     .FILL x005E     ; ASCII representation of a minus sign '^'

SP      .FILL x0020     ; ASCII representation of a space ' '
ZERO    .FILL x0030     ; ASCII offset for ASCII->Integer conversions
LF      .FILL x000A     ; ASCII representation of linefeed '\n'

.END