Slide 08b - Control Structure_Loop

8/10/2019 Slide 08b - Control Structure_Loop

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LOOP

(Part 2)

for

whiledo-while

1


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TK1913-C Programming 2

Loop :for

Condition is tested first

Loop is controlled by a counter

Syntaxes

for (initial value ; condition; update counter)statement;

Or

for (initial value ; condition; update counter) {

statement;

statement;

}


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Example

Write a program which does the following:

Reads 5 integers and displays the sum of all

integers

Input example: 3 6 4 1 2

Output example: 16


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Recall the flowchart

counter 1, sum 0

counter < 6

sumsum+ x

false

true

counter++

output sum

input x


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Note the initial

value of iand condition

i 1, sum 0

i < 6

sumsum+ x

false

true

i++

output sum

input xHow many times

does the loop get

executed?


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i 0, sum 0

i < 6

sumsum+ x

false

true

i++

output sum


does the loop get

executed?


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i 0, sum 0

i < 5

sumsum+ x

false

true

i++

output sum


does the loop get

executed?


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The C statements:

int x, sum, i;

sum = 0;

for (i = 0; i < 5; i++) {scanf(%d,&x);

sum = sum + x;

}printf(%d,sum);


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i 0, sum 0

i < 5

sumsum+ x

false

true

i++

output sum

input x

int x, sum, i;

sum = 0;

for (i = 0; i < 5; i++) {scanf(%d,&x);

sum = sum + x;

}printf(%d,sum);


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Example:for (num = 1; num


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for statement



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for

while

do-while


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Loop: while

Condition is tested first

Loop is controlled by condition or a counter

Syntax

while (condition)statement;

Or

while (condition) {

statement;

statement;}


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Recall this example:

Given an exam marks as input, display theappropriate message based on the rules below:

If marks is greater than 49, display PASS,

otherwise display FAIL

However, for input outside the 0-100 range,

display WRONG INPUT and prompt the

user to input again until a valid input is

entered


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false

true

input m

m100

m>49 PASS

FAIL

true

false

WRONG INPUT

input m

Exercise:

Convert this

flowchart to aC program


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int marks;

scanf(%d,&marks);while (marks100) {

printf(WRONG INPUT);

scanf(%d,&marks);

}

if (marks>49) {

printf(PASS);

elseprintf(FAIL);

}

Double

Selection


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Exercise

Given a set of integerswith the last one being 999

Display the summation ofall the integers.

Input example:

1 3 23 999

Output example:

Sum = 27

Draw the

flowchart for

this problem

S ti l t ll d l


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Sentinel-controlled loop

true

x!=999

sumsum+x

false

input x

sum=0

input x

output sum

#include

void main() {int sum, x;

sum = 0;

scanf(%d, &x);

while (x != 999) {

sum = sum + x;

scanf(%d, &x);

}printf(The sum : %d\n, sum);

}


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int sum, x;

sum = 0;

scanf(%d, &x);while (x != 999) {

sum = sum + x;

scanf(%d, &x);

}printf(\nThe sum : %d\n, sum);

?

?x

sum 0

1

_1

1 != 999

0+11

1 3

33 != 999

1+34

1 3 23

2323 != 999

4+2327

1 3 23 999

999999 != 999

The sum : 27


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Do-while Loop

Statements in the loop are executed first (at leastonc, and condition is tested last

Loop is controlled by a condition or counter

Syntax

do {

statement;

statement;

} while (condition);statement;

??? ???

65 67

66

67

68


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do-while statement

Example :printf(Input start and end value : );

scanf(%d %d, &start, &end);

do {

printf(%c (%d)\n, start, start);

start++;

} while (start


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continuestatement

Example:for ( i = 0; i


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Now what can you

conclude about

continue?

Input a value between 1-7:

Input a value between 1-7: 4






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breakstatement

printf(Input a value between 1 7: );

scanf(%d,&value);

for (i = 1; i


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Now what can you

conclude about

break?


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TK1913 C Programming 36

End of 1sthalf of the semester

Yes !! Thats all?Whats next???

1 week HOLIDAY

on the way

Slide 08b - Control Structure_Loop

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