Một số lưu ý khi dạy học phần "mảng hai chiều" (Tin học 11)

MOT SO LUU Y KH I DAY HOG PHA N "MAN G HA I CHIEU " (Ti n ho c 11]

O TS. TRAN DOAN VINH*

Trong chuang trinh Tin hoc 11, hoc sinh

(HS) eta dugc Idm quen vdi kieu dd lieu

mang mdt chieu. Vdi kieu du lieu ndy dd

dap ung dugc nhung yeu cdu khi bieu dien du

lieu cua cdc bdi todn trong thuc te. Tuy nhien,

con cd mdt kieu du lieu md chung ta khdng

the khdng gidi thieu cho HS trong hgc tap ngdn

ngu lap trinh Pascal, dd Id «mdng hai chieu".

1. Nhung kien thuc ca bdn HS can dgt

dugc trong hgc tap phdn «mdng hai chieu"

Mang hai chieu la bdng cdc phdn tu cung

kieu, Id mang mdt chieu md mdi phan tu

cua nd Igi Id mdt mang mdt chieu. Cd hai

cdch khai bdo kieu du lieu mang hai chieu:

khai bdo gian tiep bien mang qua kieu mang

hai chieu vd khai bdo gian tiep bien mang

hai chieu.

Gidng nhu khi khai bdo kieu du lieu mang

mdt chieu, ngudi lap trinh can phdi xdc djnh

kieu cua cdc phdn tu tgo nen mang vd kieu

chi sd. Cdch xdc djnh kieu chi sd van nhu dd

biet d kieu mang mdt chieu, chi khdc Id d

mang hai chieu can xdc dinh hai chi sd, hai

chi sd dd ddc lap vdi nhau. Cung nhu d mang

mdt chieu, trong mang hai chieu, cdc thao

tdc nhdp, xudt hay xu li mdi phdn tu cua mang

phdi tudn theo quy dinh kieu phdn tu cua

mang. Viec thuc hien cdc thao tdc ndo dd

(nhdp, xudt hay xu li) Idn luat tren cdc phdn

tu cua mang hai chieu thudng gdn vdi hai

cdu lenh f or-d o long nhau.

2. «Mdng hai chieu" vd mdt sd luu y

trong qua trinh dgy hgc

1) Khai bdo mang hai chieu. Khai bdo

mang hai chieu cd dgng tdng qudt nhu sau:

Cdch /: Khai bdo true tiep bien mang hai

chieu: var<ten bien mdng>: arra y [kieu chi

sd ddng, kieu chi sd cdt] of <kieu phdn tu>.

Cdch 2: Khai bdo gian tiep bien mdng qua

kieu mdng hai chieu: Typ e <ten kieu

Tap chi Giao due so 260 (k. 2.4/2011)

mdng>=array [kieu chi sd ddng, kieu chi sd

cdt] of <kieu phdn tu>; var <ten bien mdng>:

<ten kieu mdng>;

Tham chieu tdi phdn tu cua mdng hai chieu

duac xdc djnh bdi ten mdng cung vdi hai chi

sd dugc cdch nhau bdi ddu phdy vd viet trong

cap dd'u ngogc [vd]. Vi dy, cdc khai bdo sau

day Id hap le:

type

ArrayReal = array[-100 . . 200,100 . .

200] of real ;

ArrayBoolean = array[-n+1..n+1,n..2*n]

of boolean;

v a r

Arraylnt: array[1..10 , 1. . 15 ] of

integer;

ArrayLong: array[0..3 *(n+1) , O..n]of

longint;

2) Mot so vi dy vd nhung van de can luu y

Vi dy 1: Tinh vd dua ra mdn hinh bdng

cuu chuang.

Chuang trinh tinh vd dua ra mdn hinh bdng

cuu chuang:

program Bangcuuchuong;

uses crt;

var

B: array[1..9, 1..10] of integer;

{B: bien mang hai chieu luu bang cuu

chuong}

I,j : integer;

Begin

clrscr;

for i:= l to 9 do

for j:= 1 to 10 do

B [ i , j ] : = i * j ;

for i:=1 to 9 do

begin

for j:=1 to 10 do write(B[i,j];4);

wr i t e1n;

end;

readln

End.

Khi chpy chuang trinh, ket qua cd dgng nhu

hinh 7 dudi day [xem hinh I j.

Tu chuang trinh tren, rut ra mdt sd luu y:

- GV cd the ggi y vd hudng ddn HS tham gia

viet dugc chuang trinh cho bdi todn ddt ra;

* Truong Dai hoc sit pham Ha Noi

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