Procedure/routine documentation: Multiply: Writer's name: Thomas Tharp Most recent update Date: 4 Nov. 2008 Brief description: Takes in two integer arguments and returns an integer equal to their product. Inputs: and Preconditions: Requires two words of input (in the form of two integers) I use: - . . . Passed on stack:
- int M1 found at SP+2 (from proc's stack frame)
- int M2 found at SP+4 (from proc's stack frame)
- Preconditions, other: Calling procedure leaves space for return value at SP+6 (from proc's stack frame)
Outputs and Postconditions: I Change in computer: - Return value on stack: Returns a word (integer)
- Postcondition I do not preserve the register values or the flags
Status: CLEAN AND DONE Internal documentation: ;//--- --- Multiply() begin--- ---;
br Mdriver
;//;;;;;;;;;;;;;;;;;int Multiply(int M1, int M2);;;;;;;;;;
M1: .equate 4
M2: .equate 2
MProd: .equate 6
Multiply: lda 0x0000,i
sta MProd,s
lda M1,s
Mwhile: BREQ MendWHLE
asra
sta M1,s
BRC Mone
BR MendONE
Mone: lda MProd,s
adda M2,s
sta MProd,s
MendONE: lda M2,s
asla
sta M2,s
lda M1,s
BR Mwhile
MendWHLE: RET0
;//;;;;;;;;;;;;;;;;;;;end of Multiply procedure;;;;;;;
;Driver for int Multiply(int,int)
str1: .ascii "\nPlease enter the first number: \x00"
str2: .ascii "\nPlease enter the second number: \x00"
Mnum1: .equate 0
Mnum2: .equate 2
MProduct: .equate 4
MDvars: .equate 6
Mdriver: subsp MDvars,i
stro str1,d
deci Mnum1,s
stro str2,d
deci Mnum2,s
;//;;;;;;;;;;;;;;Begin call for Multiply(Mnum1,Mnum2)
lda Mnum1,s
sta -4,s;//stores Mnum1 above the sp, leaving room for the return value
lda Mnum2,s
sta -6,s;//stores Mnum2 above Mnum1
subsp 6,i;//pushes return, Mnum1, and Mnum2 above the SP
call Multiply
addsp 6,i;//pops entire call frame, returning SP to end of the driver stack frame
lda -2,s;//pulls the return value from above the SP where the procedure stored it
;//;;;;;;;;;;;;;;;End call for Multiply
sta MProduct,s; stores the return in a local for later use
charo '\n',i
deco Mnum1,s
charo '*',i
deco Mnum2,s
charo '=',i
deco MProduct,s
addsp MDvars,i
STOP
.end
;//--- --- --Multiply() end--- ---;
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If anyone but you uses it, your locals "should" conform to our differential naming code, but since nobody's last name begins with M I guess you're ok.