11-Ham

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

TIN HC I CNGBi 11. Hm

Ni dung

11.1. Khi nim hm

11.2. Khai bo v s dng hm

11.3. Phm vi ca bin

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2Ni dung

11.1. Khi nim hm

11.1.1. Khi nim chng trnh con

11.1.2. Phn loi chng trnh con


11.3. Phm vi ca bin

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11.1.1. Khi nim chng trnh con

Khi nim L mt chng trnh nm trong mt chng

trnh ln hn nhm thc hin mt nhim v c th

Vai tr Chia nh chng trnh ra thnh tng phn

qun l => Phng php lp trnh c cu trc

C th s dng li nhiu ln: printf, scanf

Chng trnh d dng c v bo tr hn

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3 Phn loi chng trnh con

Hm: tr v gi tr trong khi th tc th khng

Trong C: Ch cho php khai bo chng trnh con l hm.

S dng kiu void vi ngha khng l kiu d liu no c chuyn th tc v dng hm

Th tc(procedure)

Chng trnh con

Hm(function)


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Phn loi hm

Hm t vit(Ngi dng nh ngha)

HM

Hm chun(C trong th vin)


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11.2.1. Khai bo hm

11.2.2. S dng hm

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11.2.1. Khai bo hm

1. Trong chng trnh ln c nhiu chng trnh con, im bt u thc hin chng trnh s thuc chng trnh con no?

2. Main l mt chng trnh con?

3. Khai bo cc chng trnh con c lp nhau/lng ln nhau?

4. Mun lp rp cc cng vic khc nhau cng thc hin, cn phi a ra li gi hm. Li gi cn cung cp nhng g?

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511.2.1. Khai bo hm

V d:

Chng trnh in ra bnh phng ca cc s t nhin t 1 n 10

Gm 2 hm:

Hm binhphuong(int x): tr v bnh phng ca x

Hm main(): vi mi s nguyn t 1 n 10, gi hm binhphuong vi mt gi tr u vo v hin th kt qu.

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#include

#include

int binhphuong(int x){

int y;

y = x * x;

return y;

}

void main(){

int i;

for (i=0; i

6 Dng u hm L thng tin trao i gia cc hm. Phn bit

gia cc hm vi nhau.

Kiu gi tr tr v: kiu d liu bt k, khng c l kiu d liu mng.

Tn hm: l tn hp l, trong C tn hm l duy nht

[] tn_hm ([danh_sch_tham_s]){

[][]

}

11.2.1. Khai bo hm

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Tham s Cho bit nhng tham s gi nh cung cp hot

ng cho hm => cc tham s hnh thc

Tham s cung cp d liu cho hm lc hot ng: tham s thc

V d: int max(int a, int b, int c)

Thn hm return

Gi hm thng qua tn hm v cc tham s thc cung cp cho hm.

Sau khi thc hin xong, tr v im m hm c gi thng qua cu lnh return hoc kt thc hm.

C php chung: return biu_thc;

11.2.1. Khai bo hm

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711.2.1. Khai bo hm#include

#include

int binhphuong(int );

void main(){

int i;

for (i=0; i

8 Cc hm th vin

Ngn ng C cung cp mt s hm th vin nh: x l vo ra, hm ton hc, hm x l xu

s dng cc hm ny chng ta ch cn khai bo nguyn mu ca chng trc khi s dng. Khai bo thng qua ch th

#include

tp_tiu_ (.h) cha cc nguyn mu hm

11.2.1. Khai bo hm

11.2.2. S dng hm

C php:

tn_hm (danh_sch_tham_s);

V d: binhphuong(0), binhphuong(1)

Lu : Nu hm nhn nhiu tham s th cc tham s ngn

cch nhau bi du phy

Lun lun cn cp du ngoc n sau tn hm

Cc tham s ca hm s nhn cc gi tr t tham s truyn vo

Thc hin ln lt cc lnh cho n khi gp lnh return/kt thc chng trnh

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911.3. Phm vi ca bin

11.3.1. Phm vi ca bin

11.3.2. Phn loi bin

11.3.3. Cu lnh static v register

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Phm vi: khi lnh, chng trnh con, chng trnh chnh

Bin khai bo trong phm vi no th s dng trong phm vi

Trong cng mt phm vi cc bin c tn khc nhau.

Tnh hung Trong hai phm vi khc

nhau c hai bin cng tn. Trong mt phm vi ny nm trong phm vi kia?

#include

#include

int i;

int binhphuong(int x){

int y;

y = x * x;

return y;

}

void main(){

int y;

for (i=0; i

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Phn loi bin Bin ton cc: bin c khai bo ngoi mi

hm, c s dng cc hm ng sau n

Bin cc b: bin c khai bo trong lnh khi hoc chng trnh con, c t trc cc cu lnh.

Ghi nh Hm main() cng l mt chng trnh con

nhng l ni chng trnh c bt u cng nh kt thc

Bin khai bo trong hm main() cng l bin cc b, ch c phm vi trong hm main().

11.3.2. Phn loi bin

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Bin static Xut pht: bin cc b ra khi phm vi th b

nh dnh cho bin c gii phng

Yu cu lu tr gi tr ca bin cc b mt cch lu di => s dng t kha static

So snh vi bin ton cc?

C php:

static tn_bin;


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11

# include

# include

void fct() {

static int count = 1;

printf("\n Day la lan goi ham fct lan thu

%2d", count++);

}

void main(){

int i;

for(i = 0; i < 10; i++) fct();

getch();

}


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Day la lan goi ham fct lan thu 1










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11.3.3. Cu lnh static, register

Bin register Thanh ghi c tc truy cp nhanh hn RAM,

b nh ngoi

Lu bin trong thanh ghi s tng tc thc hin chng trnh

C php

register tn_bin;

Lu : s lng bin register khng nhiu v thng ch vi kiu d liu nh nh int, char

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Tho lun

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