program control repetition

8/12/2019 Program Control Repetition

1/33


2/33

Program Control: Repetition

Subject : T0016 ALGORITHM AND PROGRAMMING

Year : 2012


3/33

3

Learning Outcomes

At the end of this session, student will be able to:

Demonstrate usage of repetition/looping controloperation in C programming language (LO2 & LO3)

T0016 - Algorithm andProgramming


4/33

4

Sub Topics

Program Control - Repetition:

Repetition Definition

For

While Do-While

Repetition Operation

Break vs Continue

Program Examples



5/33

5

Repetition Definition

One or more instruction repeated for certain amount oftime

Number of repetition can be predefined (hard-coded in

program) or defined later at run time

Repetition/looping operation: for

while do-while



6/33

6

Repetition: FOR

Syntax:

for(exp1; exp2; exp3) statement;or:

for(exp1; exp2; exp3){statement1;statement2;.

}

exp1: initializationexp2: conditionalexp3: increment or decrementexp1, exp2 and exp3 are optional



7/33

7

Repetition: FOR

exp1 and exp3 can consist of several expression separated withcomma

Example:

void reverse(char ss[]){

int c,i,j;

for(i=0, j=strlen(ss)-1; i


8/33

8

Repetition: FOR

Flow Chart of FORStatement


true

false

statements

exp2

exp3

exp1


9/33

9

Repetition: FOR

Example:

for (x=1; x


10/33

10

Repetition: FOR

Example:

Program to print out numbers from 1 to 10

Program to print out numbers from 10 to 1


#include

int main()

{int x;

for( x =1 ; x=1 ; x--) printf( "%d\n", x);

return(0);

}


11/33

11

Repetition: FOR

Example:Calculating average of monthly expenses:

Week Expenses

1 Rp. 32.000,-

2 Rp. 29.000,-

3 Rp. 33.000,-

4 Rp. 24.000,-

Algorithm :

1. Create and empty total2. Read from keyboard and save to data

3. Add data to total

4. Repeat 2 and 3 four times

5. Average = total / 4T0016 - Algorithm and

Programming


12/33

12

Repetition: FOR

Example: (Calculating average of monthly expenses)


/*----------------------------------*/

/* Program Averaging */

/*----------------------------------*/

#include

int main(){

float data, total, average;

int x;

total = 0.0;

for( x = 1; x


13/33

13

Repetition: FOR

Infinite Loop

Loop with no stop condition can use for-loop byremoving all parameters (exp1, exp2, exp3). To end

the loop use break.

Nested Loop

Loop in a loop. The repetition operation will start from

the inner side loop.



14/33

14

Repetition: FOR


for (int x=1;x=1; y--)

printf(%d %d ,x,y);

Output :

1 5 1 4 1 3 .. 2 5 2 4 .. 5 1

int x, y;

for (x=1;x=1; y--)

printf(%d %d ,x,y);

C

C++

NESTED LOOP


15/33

15

Repetition: FOR

Example: (Truth Table)


/*-----------------------------------

Program: the truth table;

------------------------------------*/

#include

int main()

{

int P,Q;

printf(==============================\n);

printf(P Q P or Q P and Q Not P P xor Q\n);

printf(==============================\n);

for(P=1; P>=0; P--)

for(Q = 1; Q>=0; Q--)printf(%4d %4d %4d %4d %4d %4d\n, P, Q, P||Q, P&&Q, !P, P^Q

);

printf(==============================\n);

}


16/33

16

Repetition: WHILE

Syntax :

while (exp) statements;

or:

while(exp){

statement1;

statement2;

..

}


Example :int counter = 1;

while ( counter


17/33


18/33


19/33

19

Repetition: WHILE

Example :

while(product


20/33

20

Repetition: WHILE


#includevoid main() {

int x;

for(x = 1; x


21/33

21

Repetition: DO-WHILE

Syntax :

do{

< statements >;

} while(exp);

Keep executing while expis true

expevaluation done after executing the statement(s)


Example :int counter=0;

do {

printf( "%d ", counter );

++counter;

} while (counter


22/33

22


Flow Chart of DO-WHILE Statement


true

false

statements

condition


23/33

23


Example:

do{printf(%d\n,counter);

} while(++counter


24/33

24


In while operation, statement block of statements maynever be executed at all if exp value is false

In do-whileon the other hand statement block of

statements will be executed min once

To end the repetition, can be done through several ways:

Sentinel

Question, should the repetition continue?



25/33

25


Example: (Question)


#include

int main()

{

int width, height, area; char repeat;

printf(Continue ? (Y/N) :);scanf(%c,&repeat);

while((toupper(repeat)) == Y) {

printf( Width : );

scanf(%d,&width);

printf( Height : );

scanf(%d,&height);

area = width*height;

printf( Area = %d\n\n,area);

printf(Continue ?(Y/N):);

scanf(%c,&repeat);

}

return(0);

}


26/33

26


Example: (Sentinel)

As sentinel, used 0 for width or height


#include

int main()

{

int width, height, area;

do{

printf( Width : );

scanf(%d,&width);

printf( Height : );

scanf(%d,&height);area = width*height;

printf( Area = %d\n\n,area);

} while((width != 0) && (height != 0));

return(0);

}


27/33

27



#include

int main() {

int x = 1;

while (x


28/33

28

Break vs Continue

break:

ending loop (for, while and do-while)

end the switch operation

continue:

skip all the rest of statements (subsequent to the skipstatement) inside a repetition, and continue normally to

the next loop



29/33


30/33

30

Break vs Continue

Example using break:


#include

int main() {

int x;for(x=1; x


31/33

31

Example Labeling

Example using labeling:


#include

int main() {

int x;for(x=1; x


32/33

32

Summary

Repetition is a condition which is one or more instructionrepeated for certain amount of time

3 types of repetition/looping in C:

for while do-while



33/33

33

References

Paul J. Dietel,Harvey M. Deitel,. 2010. C : how to program. PEAPH.New Jersey. ISBN:978-0-13-705966-9 Chapter 3 & 4

Doing the Same Thing Over and Over:http://aelinik.free.fr/c/ch07.htm

http://aelinik.free.fr/c/ch07.htmhttp://aelinik.free.fr/c/ch07.htm

program control repetition

Documents