08-cac cau truc lap trinh trong c

1TRNG I HC BCH KHOA H NIVIN CNG NGH THNG TIN V TRUYN THNG

TIN HC I CNGBi 8. Cc cu trc lp trnh trong C

Ni dung

8.1. Cu trc lnh khi

8.2. Cu trc r nhnh8.2.1. Cu trc if, if else

8.2.2. Cu trc la chn switch

8.3. Cu trc lp8.3.1. Vng lp for

8.3.2. Vng lp while

8.4. Cc lnh thay i cu trc lp trnh8.4.1. continue

8.4.2. break

2

8.1. Cu trc lnh khi

Th hin cu trc tun t Lnh khi l dy cc cu lnh c t trong

cp du ngoc nhn {}{lenh_1;lenh_2;.lenh_n;

}

C cho php khai bo bin trong lnh khi, nhng phn khai bo phi nm trc cu lnh.

3

8.1. Cu trc lnh khi (2)

Lnh khi lng nhau: Trong mt lnh khi c th cha lnh khi khc S lng nhau l khng hn ch{

lenh;{

lenh;...

}

}

4


V d:#include

#include

void main()

//Noi dung cua ham main() cung la mot khoi lenh

{

// khai bao bien

int c = 10;

printf(Gia tri cua c = %d day la c ngoai,c);// bat dau mot khoi lenh khac{

int c = 10;printf(\n Gia tri cua c = %d day la c trong,c);printf(\n Tang gia tri cua c them 10 don vi);c = c + 10;printf(\n Gia tri cua c = %d day la c trong,c);

}printf(\n Gia tri cua c = %d day la c ngoai,c);getch();

}// ket thuc khoi lenh cua ham main()

5


Kt qu:

Gia tri cua c = 10 day la c ngoai

Gia tri cua c = 10 day la c trong

Tang gia tri cua c them 10 don vi

Gia tri cua c = 20 day la c trong

Gia tri cua c = 10 day la c ngoai

6

Ni dung

8.1. Cu trc lnh khi

8.2. Cu trc r nhnh 8.2.1. Cu trc if, if else


8.3. Cu trc lp 8.3.1. Vng lp for

8.3.2. Vng lp while

8.4. Cc lnh thay i cu trc lp trnh 8.4.1. continue

8.4.2. break

7

Cu trc r nhnh

Nu biu thc iu kin ng (gi tr chn l l True) thc hin cng vic 1.

8

Nu biu thc iu kin ng (gi tr chn l l True) thc hin cng vic 1.

Nu biu thc iu kin sai (gi tr chn l l False) thc hin cng vic 2.

3 C php cu trc if

if (bieu_thuc_dieu_kien)

lenh;

C php cu trc if else

if (bieu_thuc_ieu_kien)

lenh_1;

else

lenh_2;

8.2.1. Cu trc if, if else

9

Biu thc iu kin

bieu_thuc_dieu_kien

Biu thc logic : !, &&, ||

Biu thc quan h : ==, !=, >, >=,

4Cu trc if...else if

R nhiu nhnhif (bieu_thuc_dieu_kien_1){

Khoi_lenh_1;}else if (bieu_thuc_dieu_kien_2){

Khoi_lenh_2;}

...else if (bieu_thuc_dieu_kien_n){

Khoi_lenh_n;}else{

Khoi_lenh_cuoi_cung;} 13

8.2.1. Cu trc if, if else (2)

V d: Bi ton tm s ln nht trong 2 s thc a v b:#include #include void main(){// khai bao bienfloat a, b, max;printf( Nhap gia tri a va b: );scanf(%f %f,&a,&b);

if(a

5Ch

Tng ng ?

if (dieu_kien)

Cong_viec_1

else Cong_viec_2;

if (dieu_kien_1)

if (dieu_kien_2)

Cong_viec_1;

else

Cong_viec_2;

if (dieu_kien)

Cong_viec_1;

if (! dieu_kien)

Cong_viec_2;if (dieu_kien_1){

if (dieu_kien_2)

Cong_viec_1;

else

Cong_viec_2;}

if (dieu_kien_1){

if (dieu_kien_2)

Cong_viec_1;}

else

Cong_viec_2; 17

?

Bi tp

Vit chng trnh c nhng chc nng sau:

1. Hin th mt bng chn sau

2. Cho php ngi dng nhp 2 s nguyn dng

3. Cho php ngi dng a ra la chn 1 chc nng. Ty theo la chn ca ngi dng, hy thc hin cng vic tng ng. Nu ngi dng nhn 1 phm khc hy thng bo v dng chng trnh.

18


C php cu trc switchswitch (bieu_thuc)

{

case gia_tri_1: lenh_1; break;

case gia_tri_2: lenh_2; break;

case gia_tri_n: lenh_n; break;

default: lenh_n+1; break;

}

Gi tr ca biu thc kim tra (bieu_thuc) phi l s nguyn:

Phi c kiu d liu l char, int, long.

Tng ng cc gi tr sau case (gia_tri_1, gia_tri_2,) cng phi l s nguyn.

Case ch ng vai tr l nhn, lnh break c s dng thot ra khi cu trc switch

19

8.2.2. Cu trc la chn switch (3)

V d: Nhp vo s nguyn khng m, a ra ngy trong tun tng ng (theo s d khi chia cho 7).#include

#include

void main()

{

int a;

printf(\nNhap mot gia tri so nguyen khong am: );

scanf(%d,&a);

20


V d (tip):

switch(a % 7)

{

case 0: printf( Chu nhat);break;

case 1: printf( Thu Hai); break;

case 2: printf( Thu Ba); break;

case 3: printf( Thu Tu); break;

case 4: printf( Thu Nam); break;

case 5: printf( Thu Sau); break;

case 6: printf( Thu Bay); break;

}

getch();

}21


Bi tp:

Trong mt nm cc thng c 30 ngy l 4, 6, 9, 11 cn cc thng c 31 ngy l 1, 3, 5, 7, 8, 10, 12. Ring thng hai c th c 28 hoc 29 ngy.

Hy vit chng trnh nhp vo 1 thng, sau a ra kt lun thng c bao nhiu ngy.

22

8.2.2. Cu trc la chn switch (6)#include #include void main () {int thang; clrscr(); printf("\n Nhap vao thang trong nam "); scanf("%d",&thang); switch(thang) {

case 1: case 3:case 5: case 7: case 8: case 10: case 12: printf("\n Thang %d co 31 ngay ",thang); break;

23


case 4:

case 6:

case 9:

case 11:

printf("\n Thang %d co 30 ngay ",thang);

break;

case 2:

printf ("\ Thang 2 co 28 hoac 29 ngay");

break;

default :

printf("\n Khong co thang %d", thang);

break;

}

getch();

}

24

7Ni dung

8.1. Cu trc lnh khi

8.2. Cu trc r nhnh8.2.1. Cu trc if, if else


8.3. Cu trc lp8.3.1. Vng lp while v do ... while

8.3.2. Vng lp for

8.4. Cc lnh thay i cu trc lp trnh8.4.1. continue

8.4.2. break

25

Cu trc lp

Nu biu thc iu kin cnng, thc hin cng vic trongvng lp

26

Thc hin cng vic trong vnglp 1 ln

Khi biu thc iu kin cnng, thc hin cng vic trongvic trong vng lp

8.3.1. Vng lp while v do...while

Mc ch: Dng thc hin lp i lp li mt cng vic trong

khi cn tha mn iu kin no .

2 cu trc:while (bieu_thuc_dieu_kien)

{

Khoi_lenh;

}

hoc

do

{

Khoi_lenh;

} while (bieu_thuc_dieu_kien);

27

8.3.2. Vng lp while v do ... while (2)

while: Kim tra gi tr ca bieu_thuc_dieu_kientrc ri mi thc hin Khoi_lenh

Cc cu lnh c th khng c thc hin ln no.

do{} while: Thc hin Khoi_lenh

trc ri mi kim tra bieu_thuc_dieu_kienca vng lp.

Cc cu lnh c thc hin t nht 1 ln.

28

88.3.2. Vng lp while v do...while (3)

bieu_thuc_dieu_kien

Biu thc logic : !, &&, ||

Biu thc quan h : ==, !=, >, >=, 10));

S dng cu trc while {...}//nhp ln u tin

printf("Nhap diem (0

9Tho lun

Vng lp v hn : Khi no xy ra? Tc hi? Trong mt s trng hp cn dng while (1) {...} th trong

vng lp phi c cc cu lnh thay i cu trc thot ra ngoi.

Vng lp hu hn : lm th no iu kin dng xy ra?

Nhn xtwhile(dieu_kien1 || dieu_kien2) { }

tng ng viwhile (1) {

if (! (dieu_kien1 || dieu_kien2) exit;

}

while(dieu_kien1 && dieu_kien2) {}

Tng ng vi ?33

8.3.2. Vng lp for

Mc ch Dng thc hin lp i lp li mt cng vic no

(thng thng vi s ln lp xc nh)

C php:for(bieu_thuc_1;bieu_thuc_2;bieu_thuc_3){

Khoi_lenh;}

Trong : bieu_thuc_1: Khi to gi tr ban u cho vng lp bieu_thuc_2: iu kin tip tc vng lp bieu_thuc_3: Thc hin bc tng ca vng lp Ch cc biu thc 1, 2, 3 c th c hoc khng

34

8.3.2. Vng lp for (2)

V d: a ra mn hnh cc s nguyn l nh hn 100

#include #include void main(){int i;for(i = 1;i

10

8.3.2. Vng lp for (4)

Kt qu thc hin

1 3 5 7 9 11 13 15 17 19

21 23 25 27 29 31 33 35 37 39

41 43 45 47 49 51 53 55 57 59

61 63 65 67 69 71 73 75 77 79

81 83 85 87 89 91 93 95 97 99

37

Ni dung

8.1. Cu trc lnh khi

8.2. Cu trc r nhnh 8.2.1. Cu trc if, if else


8.3. Cu trc lp 8.3.1. Vng lp for

8.3.2. Vng lp while

8.4. Cc lnh thay i cu trc lp trnh 8.4.1. continue

8.4.2. break

38

8.4. Cc lnh thay i cu trc lp trnh

i vi cc lnh lp: while, do{...} while, hoc for

Thay i vic thc hin lnh trong vng lp C cung cp 2 lnh: continue;

break;

39


continue

B qua vic thc hin cc cu lnh nm sau lnh continue trong thn vng lp.

Chuyn sang thc hin mt vng lp mi

break

Thot khi vng lp ngay c khi biu thc iu kin ca vng lp vn cn c tha mn.

40

11


V d:#include #include void main(){int i;for(i = 1;i

12

Cu hi ?

45

08-cac cau truc lap trinh trong c

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