1. The document discusses different types of loops in C programming - while loops, for loops, and do-while loops. It provides examples of using each loop type to iterate through ranges of numbers and add them. 2. Key loop concepts covered include using break and continue to exit or skip iterations, transforming while loops into equivalent for loops, and nested loops. 3. Examples demonstrate using loops to find combinations that sum to a target, determine the largest number such that successive integers sum below a threshold, and calculate running totals in nested loops.

1. Loop: while, do-while, for

2. contents
 Loop statement:
– While statement
– For statement
– do-while statement
 Statement for loop:
– break, continue,
 Examples
2

3. While Statement
 while statement type 1
– Repeat statement block( {…} ) while expression is true
F
expression
expression while( expression )
T
A
{
A C A;
B;
B
B }
C C;
3

4. While Statement
 while statement type 2
– In C world, 0(zero) means FALSE and other values means TRUE
– So while(1) indefinitely repeats its statement block
– You should place if…break in statement block for program to
escape from loops
while( 1 )
{
A A;
if( !expression ) break ;
F B;
expression }
T
B C C;
4

5. While Statement
 Note
while (1) i++; /* infinite loop */
while(5/3) i++;
while(-1) i++;
while(0) i++; /*naver runs*/
5

6. While Statement
 Transform type1 to type2
A A;
A
F while( expression )
expression
F {
expression T B;
T B C A;
B C }
A C;
6

7. Do-while Statement
 Special form of while statement 1
– while statement checks expression before executing
statements in the loop.
– On the contrary, do-while statement check expression
after executing statements in the loop.
do
A {
A;
B;
B
} while( expression ) ;
F
expression C;
T
C
7

8. For Statement
 Special form of while statement 2
for( A ; expression ; D)
A
{
F B;
expression C;
T }
B E E;
C
A: initial statement of loop statements
D D: end statement of loop statements
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9. For Statement
 for statement vs. while statement
for ( expr1; expr2; expr3 ) expr1;
while (expr2)
{
{
statement ;
statement ;
... ...
} expr3;
next statement ; }
next statement ;
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10. For Statement
 Example: Add even numbers from 1 to 100
Start int i, sum ;
sum = 0 ;
Var i, sum i=2;
while( i <= 100 ) {
sum = sum + i ;
sum <- 0 i =+ 2 ;
}
i <- 2 printf( “%dn”, sum ) ;
F int i, sum ;
i  100 sum = 0 ;
T
sum for( i = 2 ; i <= 100 ; i =+ 2) {
sum <- sum + i sum = sum + i ;
}
i <- i + 2 Stop printf( “%dn”, sum ) ;
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11. For Statement
 Example: Read 10 numbers and sum up those
int i, n ; int i, n ;
sum= 0 ; sum = 0 ;
i= 0 ; for( i = 0 ; i < 10 ; i++ )
while ( i < 10) { {
scanf( “%d”, &n ) ; scanf( “%d”, &n ) ;
sum += n ; sum += n ;
i++ ; }
} printf( “%dn”, sum ) ;
printf( “%dn”, sum ) ;
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12. For Statement
 Loop from 0 to n-1
for ( i = 0; i < n; i++ ) A;
 Loop from 1 to n
for ( i = 1; i <= n; i++ ) A;
 Loop from n-1 to 0
for ( i = n -1; i >= 0; i-- ) A;
 Loop from n to 1
for ( i = n; i > 0; i-- ) A;
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13. Break Statement
 break
– Exit from the current loop or switch statement to terminate
while(A) {
B;
while(C) {
D;
if( E ) break;
F;
}
G;
if( H ) break ;
I ;
}
J;
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14. Continue Statement
 continue
– Skip the rest of the statements in the loop
while(A) {
B;
while(C) {
D;
if( E ) continue;
F;
}
G;
if( H ) continue ;
I;
}
J;
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15. Continue Statement
 continue
while(A) { while(A) {
B; B;
while(C) { while(C) {
D; D;
if( E ) continue; if( !E ) {
F; F;
G; G;
} }
H; }
if( I ) continue ; H;
J; if( !I ) {
K; J;
} K;
L; }
}
L;
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16. Example
 Print all combinations of three numbers of
which sum equals to seven
007 #include <stdio.h>
016
025 void main(void)
034 {
… int i, j, k ;
502
511 for ( i = 0; i <= 7; ++i ) {
… for( j = 0; j <= 7; ++j ) {
610 for ( k = 0; k <= 7; ++k ) {
700 if ( i + j + k == 7 )
printf( "%d %d %dn", i, j, k );
}
}
}
return ;
}
16

17. Example 1
 Add all integers between 1 and 100
Start #include <stdio.h>
main() {
Var i, sum int i, sum ;
i =0;
i <- 1 sum = 0 ;
while( i <= 100 )
{
sum <- 0 sum = sum + i ;
i=i+1;
F }
i  100
printf( “%d”, sum ) ;
T
sum return ;
sum <- sum + i }
i <- i + 1 Stop
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18. Example 1-1
 Add all integers between 1 and 100
Start #include <stdio.h>
main() {
Var i, sum int i, sum ;
i =0;
i <- 1 sum = 0 ;
while( i <= 100 )
{
sum <- 0 sum = sum + i ;
i=i+1;
}
i  100
printf( “%d”, sum ) ;
sum <- sum + i sum return ;
}
i <- i + 1
Stop
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19. Example 2
 Add all even integers between 1 and 100
Start #include <stdio.h>
main() {
Var i, sum int i, sum ;
i =0;
i <- 1, sum <- 0 sum = 0 ;
while( i <= 100 )
{
i  100 if( i % 2 == 0 )
{
i is even ? sum sum = sum + i ;
F }
T i=i+1;
}
sum <- sum + i
Stop
printf( “%d”, sum ) ;
i <- i + 1 return ;
}
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20. Example 3
 Find the largest n such that 1+2+…+n<1000
#include <stdio.h>
Start
main() {
Var n, sum int n, sum ;
n =1;
n <- 1, sum <- 0 sum = 0 ;
while( 1)
{
sum <- sum + n sum = sum + n ;
if( sum < 1000) break ;
n=n+1;
F n-1 }
sum < 1000
T printf( “%d”, n-2 ) ;
n <- n + 1 Stop return ;
}
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21. Example 3-1
 Find the largest n such that 1+2+…+n<1000
Start
#include <stdio.h>
main() {
Var n, sum
int n, sum ;
n <- 1, sum <- 0 n =1;
sum = 0 ;
sum = sum + n ;
sum <- sum + n
while( sum < 1000 )
{
sum < 1000 n-1
n=n+1;
sum = sum + n ;
}
n <- n + 1
Stop
printf( “%d”, n-2 ) ;
sum <- sum + n
return ;
}
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22. Example 4
 (1+1+…+1)+ … + (10+10+…+10)
Start
#include <stdio.h> #include <stdio.h>
Var a, b, sum
main() main()
{ {
a = 1, sum = 0 int a, b, sum; int a, b, sum;
sum = 0 ; sum = 0 ;
a  10 a=1; for( a=1; a<=10 ; a++ )
sum while( a <= 10 ) {
{ for( b=1; b<=10 ; b++ )
b <- 1 b=1; {
while( b <= 10 ) sum = sum + a ;
Stop { }
b  10 sum = sum + a ; }
b=b+1;
sum = sum+ a } return ;
a=a+1; }
}
b=b+1
return ;
}
a=a+1
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23. Example 5
 (2*1+2*2+…+2*9)+ … + (9*1+9*2+…+9*9)
Start
#include <stdio.h> #include <stdio.h>
Var a, b, sum
main() main()
{ {
a = 2, sum = 0 int a, b, sum; int a, b, sum;
sum = 0 ; sum = 0 ;
a9 a=2; for( a=2; a<=9 ; a++ )
sum while( a <= 9 ) {
{ for( b=1; b<=9 ; b++ )
b <- 1 b=1; {
while( b <= 9 ) sum = sum + a*b ;
Stop { }
b9 sum = sum + a*b ; }
b=b+1;
sum = sum+ a * b } return ;
a=a+1; }
}
b=b+1
return ;
}
a=a+1
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24. Example 6
 1+(1+2)+(1+2+3)+......+(1+....+10)
Start #include <stdio.h> #include <stdio.h>
main() main()
Var n, a, { {
sum int n, a, sum ; int a, b, sum;
n=1; sum = 0 ;
n <- 1, sum <- 0 a=1; for( n=1; n<=10 ; n++ )
sum = 0 ; {
for( a=1; a<=n ; a++ )
n  10 while( n <= 10 ) {
{ sum = sum + a ;
a=1; }
a <- 1 sum while( a <= n ) }
{
an sum = sum + a ; return ;
a=a+1; }
Stop }
sum <- sum + a n=n+1;
}
a <- a + 1
printf( “%d”, sum ) ;
return ;
n <- n + 1 }
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