Control Structures

Сентябрь 3, 2022

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Control Structures

Содержание

2. 2.15 Essentials of Counter-Controlled Repetition Counter-controlled repetition requires Name of control variable/loop counter Initial value of
3. 1 // Fig. 2.16: fig02_16.cpp 2 // Counter-controlled repetition. 3 #include 4 5 using std::cout; 6
4. 2.15 Essentials of Counter-Controlled Repetition The declaration int counter = 1; Names counter Declares counter to
6. 2.16 for Repetition Structure General format when using for loops for ( initialization; LoopContinuationTest; increment )
7. 1 // Fig. 2.17: fig02_17.cpp 2 // Counter-controlled repetition with the for structure. 3 #include 4
8. 2.16 for Repetition Structure for loops can usually be rewritten as while loops initialization; while (
9. 1 // Fig. 2.20: fig02_20.cpp 2 // Summation with for. 3 #include 4 5 using std::cout;
10. 2.17 Examples Using the for Structure Program to calculate compound interest A person invests $1000.00 in
11. 1 // Fig. 2.21: fig02_21.cpp 2 // Calculating compound interest. 3 #include 4 5 using std::cout;
12. 24 // output table column heads 25 cout 26 27 // set floating-point number format 28
13. Year Amount on deposit 1 1050.00 2 1102.50 3 1157.63 4 1215.51 5 1276.28 6 1340.10
14. 2.17.1 for Repetition Structure Flowchart
15. 2.19 do/while Repetition Structure Similar to while structure Makes loop continuation test at end, not beginning
16. 2.19 do/while Repetition Structure
17. 1 // Fig. 2.24: fig02_24.cpp 2 // Using the do/while repetition structure. 3 #include 4 5
18. 2.20 break and continue Statements break statement Immediate exit from while, for, do/while, switch Program continues
19. 1 // Fig. 2.26: fig02_26.cpp 2 // Using the break statement in a for structure. 3
20. 26 27 return 0; // indicate successful termination 28 29 } // end function main 1
21. 2.20 break and continue Statements continue statement Used in while, for, do/while Skips remainder of loop
22. 1 // Fig. 2.27: fig02_27.cpp 2 // Using the continue statement in a for structure. 3
23. 26 27 } // end function main 1 2 3 4 6 7 8 9 10
24. 2.21 Structured-Programming Summary Structured programming Programs easier to understand, test, debug and modify Rules for structured
25. 2.21 Structured-Programming Summary Representation of Rule 3 (replacing any rectangle with a control structure)
26. 2.21 Structured-Programming Summary All programs broken down into Sequence Selection if, if/else, or switch Any selection
27. Readings: C++ How to Program, By H. M. Deitel Chapter 5. Control Statements: Part 2
29. Скачать презентацию

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2.15 Essentials of Counter-Controlled Repetition
Counter-controlled repetition requires
Name of control variable/loop counter
Initial value

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

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1 // Fig. 2.16: fig02_16.cpp
2 // 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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2.15 Essentials of Counter-Controlled Repetition
The declaration
int counter = 1;
Names counter
Declares counter to

be an integer
Reserves space for counter in memory
Sets counter to an initial value of 1

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2.16 for Repetition Structure
General format when using for loops
for ( initialization; LoopContinuationTest;

increment )
statement
Example
for( int counter = 1; counter <= 10; counter++ )
cout << counter << endl;
Prints integers from one to ten

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1 // Fig. 2.17: fig02_17.cpp
2 // 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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2.16 for Repetition Structure
for loops can usually be rewritten as while 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;

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1 // Fig. 2.20: fig02_20.cpp
2 // 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

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2.17 Examples Using the for Structure
Program to calculate compound interest
A 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

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1 // Fig. 2.21: fig02_21.cpp
2 // 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

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24 // output table column heads
25 cout << "Year" << setw(

21 ) << "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

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Year Amount on deposit
1 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

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2.17.1 for Repetition Structure Flowchart

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2.19 do/while Repetition Structure
Similar to while structure
Makes loop continuation test at end,

not beginning
Loop body executes at least once
Format
do {
statement
} while ( condition );

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2.19 do/while Repetition Structure

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1 // Fig. 2.24: fig02_24.cpp
2 // 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

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2.20 break and continue Statements
break statement
Immediate exit from while, for, do/while, switch
Program

continues with first statement after structure
Common uses
Escape early from a loop
Skip the remainder of switch

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1 // Fig. 2.26: fig02_26.cpp
2 // 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;

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26
27 return 0; // indicate successful termination
28
29 } //

end function main

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

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2.20 break and continue Statements
continue statement
Used in while, for, do/while
Skips remainder 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

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1 // Fig. 2.27: fig02_27.cpp
2 // 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

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26
27 } // end function main
1 2 3 4 6

7 8 9 10
Used continue to skip printing the value 5

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2.21 Structured-Programming Summary
Structured programming
Programs easier to understand, test, debug and modify
Rules 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

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2.21 Structured-Programming Summary
Representation of Rule 3 (replacing any rectangle with a control

structure)

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2.21 Structured-Programming Summary
All programs broken down into
Sequence
Selection
if, if/else, or switch
Any selection

can be rewritten as an if statement
Repetition
while, do/while or for
Any repetition structure can be rewritten as a while statement

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Control Structures

Содержание

2.15 Essentials of Counter-Controlled RepetitionCounter-controlled repetition requiresName of control variable/loop counterInitial value

1 // Fig. 2.16: fig02_16.cpp2 // Counter-controlled repetition.3 #include 4 5

2.15 Essentials of Counter-Controlled RepetitionThe declarationint counter = 1;Names counterDeclares counter to

2.16 for Repetition StructureGeneral format when using for loopsfor ( initialization; LoopContinuationTest;

1 // Fig. 2.17: fig02_17.cpp2 // Counter-controlled repetition with the for

2.16 for Repetition Structurefor loops can usually be rewritten as while loopsinitialization;while

1 // Fig. 2.20: fig02_20.cpp2 // Summation with for.3 #include 4

2.17 Examples Using the for StructureProgram to calculate compound interestA person

1 // Fig. 2.21: fig02_21.cpp2 // Calculating compound interest.3 #include 4

24 // output table column heads25 cout << "Year" << setw(

Year Amount on deposit 1 1050.00 2 1102.50 3 1157.63 4

2.17.1 for Repetition Structure Flowchart

2.19 do/while Repetition StructureSimilar to while structureMakes loop continuation test at end,

2.19 do/while Repetition Structure

1 // Fig. 2.24: fig02_24.cpp2 // Using the do/while repetition structure.3

2.20 break and continue Statementsbreak statementImmediate exit from while, for, do/while, switchProgram

1 // Fig. 2.26: fig02_26.cpp2 // Using the break statement in

26 27 return 0; // indicate successful termination28 29 } //

2.20 break and continue Statementscontinue statementUsed in while, for, do/whileSkips remainder of

1 // Fig. 2.27: fig02_27.cpp2 // Using the continue statement in

26 27 } // end function main1 2 3 4 6

2.21 Structured-Programming SummaryStructured programmingPrograms easier to understand, test, debug and modifyRules for

2.21 Structured-Programming SummaryRepresentation of Rule 3 (replacing any rectangle with a control

2.21 Structured-Programming SummaryAll programs broken down intoSequenceSelectionif, if/else, or switch Any selection

Readings:C++ How to Program, By H. M. DeitelChapter 5. Control Statements: Part 2

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