ch5 Flashcards
ch5 checkpoint 5.1 What will the following program segments display? A) x = 2; y = x++; cout << x << y;
A) 32
B) x = 2;
y = ++x;
Cout«_space;x «_space;y;
33
C) x = 2;
y = 4;
cout«_space;x++«–y;
C) 23
D) x = 2;
y = 2 * x++;
cout «_space;x «_space;y;
D) 34
E) x = 99; if (x++ < 100) cout "It is true!\n"; else cout << "It is false!\n";
E) It is true!
F) x = 0; if (++x) cout << "It is true!\n"; else cout << "It is false!\n";
F) It is true!
5.2 Write an input validation loop that asks the user to enter a number in the range of
10 through 25.
5.2 int number;
cout «_space;“Enter a number in the range 10 through 25: “;
cin»_space; number;
while (number < 10 || number > 25)
{
cout «_space;“Error! The number must be in the range “
«_space;“of 10 through 25. Enter a valid number: “;
cin»_space; number;
}
5.3 Write an input validation loop that asks the user to enter ‘Y’ , ‘y’ , ‘N’ , or ‘n’ .
5.3 char letter;
cout << "Enter Y for yes or N for no: ";
cin >> letter;
while (letter != 'Y' && letter != 'y' &&
letter != 'N' && letter != 'n')
{
cout << "Error! Enter either Y or N: ";
cin >> letter;
}5.4 Write an input validation loop that asks the user to enter “Yes” or “No” .
5.4 string input;
cout << "Enter Yes or No: ";
cin >> input;
while ( (input != "Yes") && (input != "No") )
{
cout << "Error! Enter either Yes or No: ";
cin >> input;
}5.5 What will the following program segments display?
A) int count = 10;
do
{
cout << "Hello World\n";
count++;
} while (count < 1);5.5 A) Hello World
B) int v = 10;
do
cout «_space;v «_space;end1;
while (v < 5);
B) 10
C) int count = 0, number = 0, limit = 4;
do
{
number += 2;
count++;
} while (count < limit);
cout << number << " " << count << endl;C)
8 4
5.6 Name the three expressions that appear inside the parentheses in the for loop’s
header.
5.6 Initialization, test, and update.
5.7 You want to write a for loop that displays I love to program 50 times. Assume
that you will use a counter variable named count.
A) What initialization expression will you use?
B) What test expression will you use?
C) What update expression will you use?
D) Write the loop.
5.7
A) int count = 1;
B) count
5.8 What will the following program segments display?
A) for (int count = 0; count
5.8 A) 0246810 B) -5-4-3-2-101234 C) 5 8 11 14 17
5.9 Write a for loop that displays your name 10 times.
5.9 for (int count = 1; count «_space;“Chris Coder\n”;
5.10 Write a for loop that displays all of the odd numbers, 1 through 49.
5.10 for (int count = 1; count «_space;count «_space;endl;
5.11 Write a for loop that displays every fifth number, zero through 100.
5.11 for (int count = 0; count «_space;count «_space;endl;
5.12 Write a for loop that repeats seven times, asking the user to enter a number. The
loop should also calculate the sum of the numbers entered.
5.12 int number, total = 0;
for (int count = 0; count < 7; count++)
{
cout << "Enter a number: ";
cin >> number;
total += number;
}5.13 In the following program segment, which variable is the counter variable and which is the accumulator? int a, x, y = 0; for (x = 0; x > a; y += a; } cout
5.13 The variable x is the counter variable. The variable y is the accumulator.
5.14 Why should you be careful when choosing a sentinel value?
5.14 You must be sure to choose a sentinel value that could not be mistaken as a member of the
data list.
5.15 How would you modify Program 5-13 so any negative value is a sentinel?
5.15 Change the while loop to read:
while (points >= 0)
5.16 What is an output file? What is an input file?
5.16 An output file is a file that data is written to. An input file is a file that data is read from.
5.17 What three steps must be taken when a file is used by a program?
- 17 1. Open the file
- Process the file
- Close the file
5.18 What is the difference between a text file and a binary file?
5.18 A text file contains data that has been encoded as text, using a scheme such ASCII or
Unicode. Even if the file contains numbers, those numbers are stored in the file as a
series of characters. As a result, the file may be opened and viewed in a text editor
such as Notepad. A binary file contains data that has not been converted to text. As a
consequence, you cannot view the contents of a binary file with a text editor.
5.19 What is the difference between sequential access and random access?
5.19 When you work with a sequential access file, you access data from the beginning of the file
to the end of the file. When you work with a random access file, you can jump directly to
any piece of data in the file without reading the data that comes before it.
5.20 What type of file stream object do you create if you want to write data to a file?
5.20 ofstream
5.21 What type of file stream object do you create if you want to read data from a file?
5.21 ifstream
5.22 Write a short program that uses a for loop to write the numbers 1 through 10 to
a file.
5.22 ofstream outputFile(“num.txt”);
for (int num = 1; num «_space;num «_space;endl;
outputFile.close();
5.23 Write a short program that opens the file created by the program you wrote for
Checkpoint 5.22, reads all of the numbers from the file, and displays them.
5.23 ifstream inputFile("num.txt");
int num;
while (inputFile >> num)
cout << num << endl;
inputFile.close();5.24 The following code has an error. Can you correct it? // Find the error and correct it. ofstream outputFile; string filename = "Test.txt"; outputFile.open(filename);
5.24 ofstream outputFile;
string filename = “Test.txt”;
outputFile.open(filename.c_str());
Short Answer
1. Why should you indent the statements in the body of a loop?
- By indenting the statements, you make them stand out from the surrounding code. This
helps you to identify at a glance the statements that are conditionally executed by a loop.
- Describe the difference between pretest loops and posttest loops.
- The main difference bt pretest loops and posttest loops is one in which the block is to be repeated until the specified condition is no longer true, and the condition is tested before the block is executed and a posttest loop is one in which the block is to be repeated until the specified condition is no longer true, and the condition is tested after the block is executed.
- Why are the statements in the body of a loop called conditionally executed
statements?
- Because they are only executed when a condition is true.
- What is the difference between the while loop and the do-while loop?
- Difference bt the while loop and the do-while loop is in while loop condition is checked at the starting of the loop, if it is true code is the loop is executed and this process is repeated till the condition becomes false and in the do-while loop the checking of condition is done at the end of the loop. so even if the condition is false, inside the loop is executed at least once
- Which loop should you use in situations where you wish the loop to repeat until the
test expression is false, and the loop should not execute if the test expression is false to
begin with?
- The while loop.
- Which loop should you use in situations where you wish the loop to repeat until the
test expression is false, but the loop should execute at least one time?
- the do-while loop is to repeat until the test expression is false, but the loop should execute at least one time
- Which loop should you use when you know the number of required iterations?
- The for loop.
- Why is it critical that counter variables be properly initialized?
- two reasons;
- counter variables are used to count the number of times the loop needs to be iterated.
- they are used as loop control variables
- Why is it critical that accumulator variables be properly initialized?
- An accumulator is used to keep a running total of numbers. In a loop, a value is usually
added to the current value of the accumulator. If it is not properly initialized, it will not contain
the correct total.
- Why should you be careful not to place a statement in the body of a for loop that
changes the value of the loop s counter variable?
- placing the counter variable in body of loop that changes value of statement will lead to un-determined termination ie. loop will probably not terminate when your expect
- What header file do you need to include in a program that performs file operations?
- fstream
- What data type do you use when you want to create a file stream object that can write
data to a file?
ofstream
- What data type do you use when you want to create a file stream object that can read
data from a file?
- ifstream
- Why should a program close a file when it s finished using it?
an unclosed file causes any unsaved data that still held in a buffer to be saved to its file. so when it is closed after manipulation, the data in the file will not be lost even if you need to read it later in the same program
- What is a file ‘s read position? Where is the read position when a file is first opened for
reading?
- A file’s read position marks the location of the next byte that will be read from the file. When
an input file is opened, its read position is initially set to the first byte in the file.
- To __________ a value means to increase it by one, and to __________ a value means
to decrease it by one.
increment/ decrement
- When the increment or decrement operator is placed before the operand (or to the
operand s left), the operator is being used in __________ mode.
- prefix
- When the increment or decrement operator is placed after the operand (or to the
operand s right), the operator is being used in __________ mode.
18.postfix
- The statement or block that is repeated is known as the __________ of the loop.
- body
- Each repetition of a loop is known as a(n) __________.
- iteration
- A loop that evaluates its test expression before each repetition is a(n) __________ loop.
- pretest
- A loop that evaluates its test expression after each repetition is a(n) __________ loop.
- posttest
- A loop that does not have a way of stopping is a(n) __________ loop.
- infinite or endless
- A(n) __________ is a variable that counts the number of times a loop repeats.
- counter
- A(n) __________ is a sum of numbers that accumulates with each iteration of a loop.
- running total
- A(n) __________ is a variable that is initialized to some starting value, usually zero,
and then has numbers added to it in each iteration of a loop.
- accumulator
- A(n) __________ is a special value that marks the end of a series of values.
- sentinel
- The __________ loop always iterates at least once.
- do-while
- The __________ and __________ loops will not iterate at all if their test expressions
are false to start with.
- while and for
- The __________ loop is ideal for situations that require a counter.
for
- Inside the for loop s parentheses, the first expression is the __________ , the second
expression is the __________ , and the third expression is the __________.
- initialization, test, update
- A loop that is inside another is called a(n) __________ loop.
- nested
- The __________ statement causes a loop to terminate immediately.
- break
- The __________ statement causes a loop to skip the remaining statements in the
current iteration.
- continue
- Write a while loop that lets the user enter a number. The number should be multiplied
by 10, and the result stored in the variable product. The loop should iterate as
long as product contains a value less than 100.
- int product = 0, num;
while (product > num;
product = num * 10;
}
- Write a do-while loop that asks the user to enter two numbers. The numbers should
be added and the sum displayed. The user should be asked if he or she wishes to perform
the operation again. If so, the loop should repeat; otherwise it should terminate.
char repeat;
do
{
double num1,num2;
cout > num1 >> num2;
cout > repeat;
} while (repear == 'Y' || repeat == 'y');- Write a for loop that displays the following set of numbers:
0, 10, 20, 30, 40, 50 . . . 1000
- for (int x = 0; x «_space;x;
- Write a loop that asks the user to enter a number. The loop should iterate 10 times
and keep a running total of the numbers entered.
int number, total = 0;
for (int i=0; i < 10; i++)
{
cout << "Enter a number: ";
cin >> number;
total +=number;
}- Write a nested loop that displays 10 rows of # characters. There should be 15 #
characters in each row.
39. for (int row = 0; row < 10; row++)
{
for (int col = 0; col < 15; col++)
cout << '#';
cout << endl;
}40. Convert the following while loop to a do-while loop:
int x = 1;
while (x > 0)
{
cout << "enter a number: ";
cin >> x;
}int x;
do
{
cout << "enter a number: ";
cin >> x;
} while (x>0);- Convert the following do-while loop to a while loop:
char sure;
do
{
cout «_space;“Are you sure you want to quit? “;
cin»_space; sure;
} while (sure != ‘Y’ && sure != ‘N’);
41. char sure = 'x';
while (sure != 'Y' && sure != 'N')
{
cout << "Are you sure you want quit? "
cin >> sure;
}42. Convert the following while loop to a for loop:
int count = 0;
while (count < 50)
{
cout << "count is " << count << endl;
count++;
}for (int count = 0; count «_space;“count is «_space;count «_space;endl;
}
43. Convert the following for loop to a while loop:
for (int x = 50; x > 0; x--)
{
cout << x << " seconds to go.\n";
}43. int x = 50;
while (x > 0)
{
cout << x << " seconds to go.\n";
x--;
}- Write code that does the following: Opens an output file with the filename
Numbers.txt, uses a loop to write the numbers 1 through 100 to the file, and then
closes the file.
44.
- Write code that does the following: Opens the Numbers.txt le that was created by
the code you wrote in question 44, reads all of the numbers from the file and displays
them, and then closes the file.
- ifstream inputFile(“Numbers.txt”);
int number;
while (inputFile»_space; number)
cout
- Modify the code that you wrote in question 45 so it adds all of the numbers read from
the file and displays their total.
46
- T F The operand of the increment and decrement operators can be any valid
mathematical expression.
- false
- T F The cout statement in the following program segment will display 5:
int x = 5;
cout «_space;x++;
- true,
- T F The cout statement in the following program segment will display 5:
int x = 5;
cout «_space;++x;
- false
- T F The while loop is a pretest loop.
- true
- T F The do-while loop is a pretest loop.
- false
- T F The for loop is a posttest loop.
- f, for loop is pretest loop
- T F It is not necessary to initialize counter variables.
- false
- T F All three of the for loop s expressions may be omitted.
- t
- T F One limitation of the for loop is that only one variable may be initialized in
the initialization expression.
- false
- T F Variables may be defined inside the body of a loop.
- t
- T F A variable may be defined in the initialization expression of the for loop.
- true
- T F In a nested loop, the outer loop executes faster than the inner loop.
- f. inner loops executed first
- T F In a nested loop, the inner loop goes through all of its iterations for every
single iteration of the outer loop.
- true
- T F To calculate the total number of iterations of a nested loop, add the number
of iterations of all the loops.
- t.
- T F The break statement causes a loop to stop the current iteration and begin the
next one.
- false
- T F The continue statement causes a terminated loop to resume.
- f. the continue statement causes a loop to stop the current iteration and begin the next one
- T F In a nested loop, the break statement only interrupts the loop it is placed in.
- true
- T F When you call an ofstream object s open member function, the specified file
will be erased if it already exists.
- t
