Control Structures

value of control variable
Condition to test for final value
Increment/decrement to

modify control variable when looping

Counter-controlled repetition.
3 #include
4
5

using std::cout;
6 using std::endl;
7
8 // function main begins program execution
9 int main()
10 {
11 int counter = 1; // initialization
12
13 while ( counter <= 10 ) { // repetition condition
14 cout << counter << endl; // display counter
15 ++counter; // increment
16
17 } // end while
18
19 return 0; // indicate successful termination
20
21 } // end function main

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2
3
4
5
6
7
8
9
10

to be an integer
Reserves space for counter in memory
Sets counter

to an initial value of 1

LoopContinuationTest; increment )
statement
Example
for( int counter = 1;

counter <= 10; counter++ )
cout << counter << endl;
Prints integers from one to ten

Counter-controlled repetition with the for structure.
3 #include
4

5 using std::cout;
6 using std::endl;
7
8 // function main begins program execution
9 int main()
10 {
11 // Initialization, repetition condition and incrementing
12 // are all included in the for structure header.
13
14 for ( int counter = 1; counter <= 10; counter++ )
15 cout << counter << endl;
16
17 return 0; // indicate successful termination
18
19 } // end function main

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2
3
4
5
6
7
8
9
10

loops
initialization;
while ( loopContinuationTest){
statement
increment;
}
Initialization and increment
For multiple

variables, use comma-separated lists
for (int i = 0, j = 0; j + i <= 10; j++, i++)
cout << j + i << endl;

Summation with for.
3 #include
4
5

using std::cout;
6 using std::endl;
7
8 // function main begins program execution
9 int main()
10 {
11 int sum = 0; // initialize sum
12
13 // sum even integers from 2 through 100
14 for ( int number = 2; number <= 100; number += 2 )
15 sum += number; // add number to sum
16
17 cout << "Sum is " << sum << endl; // output sum
18 return 0; // successful termination
19
20 } // end function main

Sum is 2550

person invests $1000.00 in a savings account yielding 5 percent

interest. Assuming that all interest is left on deposit in the account, calculate and print the amount of money in the account at the end of each year for 10 years. Use the following formula for determining these amounts:
a = p(1+r)
p is the original amount invested (i.e., the principal),
r is the annual interest rate,
n is the number of years and
a is the amount on deposit at the end of the n-th year

n

Calculating compound interest.
3 #include
4
5

using std::cout;
6 using std::endl;
7 using std::ios;
8 using std::fixed;
9
10 #include
11
12 using std::setw;
13 using std::setprecision;
14
15 #include // enables program to use function pow
16
17 // function main begins program execution
18 int main()
19 {
20 double amount; // amount on deposit
21 double principal = 1000.0; // starting principal
22 double rate = .05; // interest rate
23

cout

"Amount on deposit" << endl;
26
27 // set floating-point number format
28 cout << fixed << setprecision( 2 );
29
30 // calculate amount on deposit for each of ten years
31 for ( int year = 1; year <= 10; year++ ) {
32
33 // calculate new amount for specified year
34 amount = principal * pow( 1.0 + rate, year );
35
36 // output one table row
37 cout << setw( 4 ) << year
38 << setw( 21 ) << amount << endl;
39
40 } // end for
41
42 return 0; // indicate successful termination
43
44 } // end function main

1050.00
2

1102.50
3 1157.63
4 1215.51
5 1276.28
6 1340.10
7 1407.10
8 1477.46
9 1551.33
10 1628.89

end, not beginning
Loop body executes at least once
Format
do {

statement
} while ( condition );

Using the do/while repetition structure.
3 #include
4

5 using std::cout;
6 using std::endl;
7
8 // function main begins program execution
9 int main()
10 {
11 int counter = 1; // initialize counter
12
13 do {
14 cout << counter << " "; // display counter
15 } while ( ++counter <= 10 ); // end do/while
16
17 cout << endl;
18
19 return 0; // indicate successful termination
20
21 } // end function main

1 2 3 4 5 6 7 8 9 10

switch
Program continues with first statement after structure
Common uses
Escape early from

a loop
Skip the remainder of switch

Using the break statement in a for structure.
3

#include
4
5 using std::cout;
6 using std::endl;
7
8 // function main begins program execution
9 int main()
10 {
11
12 int x; // x declared here so it can be used after the loop
13
14 // loop 10 times
15 for ( x = 1; x <= 10; x++ ) {
16
17 // if x is 5, terminate loop
18 if ( x == 5 )
19 break; // break loop only if x is 5
20
21 cout << x << " "; // display value of x
22
23 } // end for
24
25 cout << "\nBroke out of loop when x became " << x << endl;

indicate successful termination
28
29 } // end function

main

1 2 3 4
Broke out of loop when x became 5

of loop body
Proceeds with next iteration of loop
while and do/while

structure
Loop-continuation test evaluated immediately after the continue statement
for structure
Increment expression executed
Next, loop-continuation test evaluated

Using the continue statement in a for structure.
3

#include
4
5 using std::cout;
6 using std::endl;
7
8 // function main begins program execution
9 int main()
10 {
11 // loop 10 times
12 for ( int x = 1; x <= 10; x++ ) {
13
14 // if x is 5, continue with next iteration of loop
15 if ( x == 5 )
16 continue; // skip remaining code in loop body
17
18 cout << x << " "; // display value of x
19
20 } // end for structure
21
22 cout << "\nUsed continue to skip printing the value 5"
23 << endl;
24
25 return 0; // indicate successful termination

3 4 6 7 8 9 10
Used continue to skip

printing the value 5

for structured programming
Only use single-entry/single-exit control structures
Rules
1) Begin with the

“simplest flowchart”
2) Any rectangle (action) can be replaced by two rectangles (actions) in sequence
3) Any rectangle (action) can be replaced by any control structure (sequence, if, if/else, switch, while, do/while or for)
4) Rules 2 and 3 can be applied in any order and multiple times

 

 

control structure)

selection can be rewritten as an if statement
Repetition
while, do/while or

for
Any repetition structure can be rewritten as a while statement