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Agendafor loopShort-handed notationHow to use break and continue

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for loop There are statements that are needed to be

repeated. The exact amount of loops (repetitions) is

known.

Example I:Calculate the sum of 1 to 1000.

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Syntaxfor (expression1; expression2; expression3){ 1st statement; 2nd statement; … nth statement;}whereexpression1: starting conditionexpression2: In-the-loop conditionexpression3: variable update condition

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Example:int counter, sum = 0;for (counter = 1; counter <=1000; counter = counter+1) { sum = sum + counter;}

printf("The sum is %d \n",sum);

SyntaxRecall that while loop uses the following formatexpression1;while (expression2) { 1st statement; … nth statement;

3rd expression;}

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Flowchart for (counter = 1; counter <=10; counter = counter+1) { statement;}

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Entry

counter = 1

counter <= 10

statement

counter = counter + 1

Exit

True

False

ExampleConsider the following program that displays the

number from 1 to 10.Compare the codes with the do loop and do-while

loop that perform the same task.

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Example#include <stdio.h> int main() { int counter; printf("Print counter from 1 to 10\n"); for (counter = 1; counter <=10; counter = counter + 1) { printf("%d ", counter); } return 0;}

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Print counter from 1 to 101 2 3 4 5 6 7 8 9 10

Short-handed notation

Operators Expressions Meanings Final values

+= c += 7 c = c + 7 10

-= d -= 4 d = d – 4 1

*= e *= 5 e = e * 5 20

/= f /= 3 f = f / 3 2

%= g %= 9 g = g % 9 3

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Useful notations in statements (assignment operators)

Let c = 3, d = 5, e = 4, f = 6, g = 12

More on short-handed notationsOperators Examples Meanings

++ ++a Increase a by 1, and use the new value of a

++ a++ Use the value of the current a, and add 1 to a afterward

-- --b Decrease b by 1, and use the new value of b

-- b-- Use the value of the current b, and subtract 1 from b

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Let a = 10, b = 5• x = ++a; // The results are: x = 11, and a = 11• y = a++; // The results are: y = 10, and a = 11• u = --b; // The results are: u = 4, and b = 4• v = b--; // The results are: v = 5, and b = 4

(Precedence) Order of operations Operators Order

++ -- + - ! right to left

* / % left to right

+ - left to right

< <= > >= left to right

== != left to right

&& left to right

|| left to right

? : right to left

= += -= *= /= %= right to left

, left to right

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Exampleon using ++

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Example#include <stdio.h>int main() { int c;

/* demonstrate postincrement */ c = 5;

printf(“%d\n”, c);printf(“%d\n”, c++); /* print c then increase */printf(“%d\n\n”, c);

/* demonstrate preincrement */ c = 5;

printf(“%d\n”, c);printf(“%d\n”, ++c); /* increase then print c */printf(“%d\n”, c);

return (0);}

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556

566

Using break and continuebreak or continue is used to re-route/jump the

path under a special circumstance.For more organized programming, avoid using break and

continue if possible.

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breakIn the loop (while, do-while, for) or switch

statement, using break results in the leaving the loop immediately.

The program continues at the statement after the loop

ExampleThe following program displays the counter using for

loop, when the counter is 5, leave the loop immediately.

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Example #include <stdio.h> void main() { int x; for (x = 1; x <= 10; x++) { if (x == 5) { /* if x is 5, terminate loop */ break; } printf("%d", x); } printf("\n Broke out of loop at x == %d\n", x); }

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1 2 3 4Broke out of loop at x == 5

continue

In the loop (while, do while, for), at the nth iteration, using continue results in the program skips the rest of statements in the current iteration. However, the program continues on the next (n+1)th iteration.

ExampleThe following program displays the counter. At the 5th

iter, printf is skipped, and continue on the 6th iter.

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Example #include <stdio.h> int main() { int x; for (x = 1; x <= 10; x++) { if (x == 5) { /* if x is 5, skip remaining code in loop body*/ continue; } printf("%d", x); } printf("\n Used continue to skip printing the value 5\n"); return; }

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1 2 3 4 6 7 8 9 10Used continue to skip printing the value 5