10.3: Implement the Program
- Page ID
- 19920
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Based on the algorithm, a program can be developed and implemented. The algorithm is expanded and the code added based on the steps outlined in the algorithm. This allows the programmer to focus on the specific issues for the current section being coded including the data types and data sizes. This example addresses only unsigned data so the unsigned divide (DIV, not IDIV) is used. Since the integer is a double-word, it must be converted into a quadword for the division. However, the result and the remainder after division will also be a double-words. Since the stack is quadwords, the entire quadword register will be pushed. The upper-order portion of the register will not be accessed, so its contents are not relevant.
One possible implementation of the algorithm is as follows:
; Simple example program to convert an
; integer into an ASCII string.
; *********************************************************
; Data declarations
section .data
; -----
; Define constants
NULL equ 0
EXIT_SUCCESS equ 0 ; successful operation
SYS_exit equ 60 ; code for terminate
; -----
; Define Data.
intNum dd 1498
section .bss
strNum resb 10
; *********************************************************
section .text
global _start
_start:
; Convert an integer to an ASCII string.
; -----
; Part A - Successive division
mov eax, dword [intNum] ; get integer
mov rcx, 0 ; digitCount = 0
mov ebx, 10 ; set for dividing by 10
divideLoop:
mov edx, 0
div ebx ; divide number by 10
push rdx ; push remainder
inc rcx ; increment digitCount
cmp eax, 0 ; if (result > 0)
jne divideLoop ; goto divideLoop
; -----
; Part B - Convert remainders and store
mov rbx, strNum ; get addr of string
mov rdi, 0 ; idx = 0
popLoop:
pop rax ; pop intDigit
add a1, "0" ; char = int + "0"
mov byte [rbx+rdi], a1 ; string[idx] = char
inc rdi ; increment idx
loop popLoop ; if (digit Count > 0)
; goto popLoop
mov byte [rbx + rdi], NULL ; string[idx] = NULL
; -----
; Done, terminate program.
last:
mov rax, SYS_exit ; call code for exit
mov rdi, EXIT_SUCCESS ; exit with success
syscall
There are many different valid implementations for this algorithm. The program should be assembled to address any typos or syntax errors.