2d barcode generator vb.net ITERATION in Software

Paint EAN13 in Software ITERATION

int main() { int n, count=0, sum=0; cout << "Enter positive integers (0 to quit):" << endl; for (;;) // "forever" { cout << "\t" << count + 1 << ": "; cin >> n; if (n <= 0) break; ++count; sum += n; } cout << "The average of those " << count << " positive numbers is " << float(sum)/count << endl; } Enter positive integers (0 to quit): 1: 4 2: 7 3: 1 4: 5 5: 2 6: 0 The average of those 5 positive numbers is 3.8

When 0 is input, the break executes, immediately terminating the for loop and transferring execution to the final output statement. Without the break statement, the ++count statement would have to be put in a conditional, or count would have to be decremented outside the loop or initialized to 1. Note that all three parts of the for loop s control mechanism are empty: for (;;). This construct is pronounced forever. Without the break, this would be an infinite loop.

When used within nested loops, the break statement applies only to the loop to which it directly belongs; outer loops will continue, unaffected by the break. This is illustrated by the following example. EXAMPLE 4.22 Using a break Statement with Nested Loops

Since multiplication is commutative (e.g., 3 4 = 4 3), multiplication tables are often presented with the numbers above the main diagonal omitted. This program modifies that of Example 4.18 on page 69 to print a triangular multiplication table: int main() { for (int x=1; x <= 12; x++) { for (int y=1; y <= 12; y++) if (y > x) break; else cout << setw(4) << x*y; cout << endl; } }

CHAP. 4]

1 2 3 4 5 6 7 8 9 10 11 12

4 6 8 10 12 14 16 18 20 22 24

9 12 15 18 21 24 27 30 33 36

16 20 24 28 32 36 40 44 48

25 30 35 40 45 50 55 60

36 42 48 54 60 66 72

49 56 63 70 77 84

64 72 81 80 90 100 88 99 110 121 96 108 120 132 144

When y > x , the execution of the inner y loop terminates and the next iteration of the outer x loop begins. For example, when x = 3, the y loop iterates 3 times (with y = 1, 2, 3), printing 3 6 9. Then on its 4th iteration, the condition (y > x) is true, so the break statement executes, transferring control immediately to the cout << endl statement (which is outside of the inner y loop). Then the outer x loop begins its 4th iteration with x = 4.

4.6 THE continue STATEMENT The break statement skips the rest of the statements in the loop s block, jumping immediately to the next statement outside of the loop. The continue statement is similar. It also skips the rest of the statements in the loop s block, but instead of terminating the loop, it transfers execution to the next iteration of the loop. It continues the loop after skipping the remaining statements in its current iteration. EXAMPLE 4.23 Using continue and break Statements

This little program illustrates the continue and break statements: int main() { int n; for (;;) { cout << "Enter int: "; cin >> n; if (n%2 == 0) continue; if (n%3 == 0) break; cout << "\tBottom of loop.\n"; } cout << "\tOutside of loop.\n"; } Enter int: 7 Bottom of loop. Enter int: 4 Enter int: 9 Outside of loop. When n has the value 7, both if conditions are false and control reaches the bottom of the loop. When n has the value 4, the first if condition is true (4 is a multiple of 2), so control skips over the rest of the statements in the loop and jumps immediately to the top of the loop again to continue with its next iteration. When n has the value 9, the first if condition is false (9 is not a multiple of 2) but the second if condition is true (9 is a multiple of 3), so control breaks out of the loop and jumps immediately to the first statement that follows the loop.