The document summarizes key concepts about input/output statements in the C++ programming language. It discusses how input streams are used for reading data from a source, while output streams are used for writing data to a destination. It provides examples of using the standard input stream cin and standard output stream cout to take user input and display output. It also demonstrates how to perform file reading and writing using ifstream and ofstream classes. Finally, it discusses formatted outputs using functions like setw and setprecision to control output formatting.

1. PROGRAMMING
LANGUAGE C++
Input/Output
Statements
Guided by Dr. DO Thi Lien

2. Input/Output
Statements
1

3. Input/Output Statements
● In the programming language C++
○ Performed using streams
○ A stream is a sequence of
characters that represent a
source or destination of data.
○ Input streams are used for
reading data from a source
○ Output streams are used for
writing data to a destination.
● In general
○ Essential components of any
programming language
○ Input statements are used to take
input from the user
○ Output statements are used to
display output to the user.
STANDARD INPUT STREAM
Command cin
Used along with >>
Example: cin >> num
STANDARD OUTPUT STREAM
Command cout
Used along with <<
Example: cout << “Hello World”

4. Example Programme: Sum Calculation
#include <iostream>
using namespace std;
int main() {
int num1, num2;
cout << "Enter two numbers:
";
cin >> num1 >> num2;
cout << "The sum of " <<
num1 << " and " << num2 << " is
" << num1 + num2 << endl;
return 0;
}
In this programme:
● Declaring two integers num1 and num2
● Prompt the user to enter two numbers with
cout
● Read the input values with cin statement and
store in 2 variables
● Calculate the sum of these numbers and
display the result to the console with cout
PROGRAMME OUTPUT
Enter two numbers: 5 7
The sum of 5 and 7 is 12

5. Basic use of the
Statements
2

6. ● Used to interact with the user and perform necessary
input/output operations.
How to use the Statements
EXAMPLE CODE C++
int num;
cout << "Enter a number: ";
cin >> num;
Steps:
Declare integer value num
Use cout to display a message “Enter a number: ” to the console
The user can enter a value which is read and stored in the variable num
using the cin statement

7. Output display
int x = 5, y = 7;
cout << "The sum of " << x << "
and " << y << " is " << x + y <<
endl;
In this code:
● Declare two integer variables x and y
● Initialise variables with values (5 and 7)
● Use the cout statement to display the sum of
two numbers to the console
● The << operator is used to concatenate values
and strings together
● Keyword endl is to insert a new line at the
end of the output.

8. File reading
and writing 3
A super strength of C++ that C does not have

9. The ifstream and ofstream classes
#include <iostream>
#include <fstream>
using namespace std;
int main() {
ifstream
inputFile("input.txt");
if (!inputFile.is_open()) {
cout << "Failed to open
file!" << endl;
return 1;
}
int num;
inputFile >> num;
cout << "The value of num is "
<< num << endl;
inputFile.close();
return 0;
}
In this code:
● Opens a file named "input.txt" for input using
the ifstream class (for read-only).
● Checks if the file was opened successfully
using the is_open() function.
● If the file was opened successfully, it reads an
integer value from the file using the >>
operator and stores it in the variable num.
● Outputs a message "The value of num is "
followed by the value of num to the console
using the cout stream.
● Finally, it closes the input file using the close()
function.
● If the console fails to open the file, it shows an
error: "Failed to open file!“
Read the file only Read and write the file

10. The ifstream and ofstream classes
#include <iostream>
#include <fstream>
using namespace std;
int main() {
ofstream myfile("example.txt");
if (myfile.is_open()) {
myfile << "This is a
line.n";
myfile << "This is another
line.n";
myfile.close();
}
else {
cout << "Unable to open
file." << endl;
}
return 0;
}
In this code:
● Opens a file named “example.txt" for output
using the ofstream class (for read and write
files).
● Checks if the file was opened successfully
using the is_open() function.
● If the file was opened successfully, it write 2
strings straight to the file:
○ This is a line.
○ This is another line.
● Finally, it closes the input file using the close()
function.
● If the console fails to open the file, it shows an
error: “Unable to open file."

11. Reading and
writing strings
4
An improvement of the string processing commands in C

12. Reading and writing strings
#include <iostream>
#include <sstream>
using namespace std;
int main() {
string input = "1,2,3,4,5";
stringstream ss(input);
string token;
while (getline(ss, token,
',')) {
cout << token << endl;
}
return 0;
}
In this code:
● Creates a string containing a list of comma-
separated values.
● Creates a string stream ss using the
stringstream class and initializes it with the
string input.
● Reads the values from the string stream
using the getline() function, which reads the
separated values and stores in the variable
token
● Output each value on a separate line on the
console
NOTE
Like any programming languages, spaces and special characters
count in the strings
Required arguments in
any programmes

13. Formatted
outputs
5 Another super-strength of the programming
language C++

14. Formatted outputs
#include <iostream>
#include <iomanip>
using namespace std;
int main() {
double pi = 3.14159;
cout << "pi: " <<
setprecision(3) << pi << endl;
cout << setw(10) <<
setfill('-') << "hello" << endl;
return 0;
}
In this code:
● Declare decimal number variable pi and store
the value for it
● Use cout to display a message "pi: " and
shows its value with precision of 3 digits
including the integer part.
● Use setw to set the string width of the whole
line (10 characters) and setfill to fill into the
blank spaces with dashes ('-'), then a
message "hello" ends the programme
FORMATTING OPTIONS
setw(), setprecision(), setfill(), …

15. ● Input/output statements are fundamental components
of C++ programming language
● I/O statements allow users to interact with the
program and provide necessary inputs and outputs to
and from the program.
● I/O statements in C++ also help users to process data
from text files, which thing C does not have
● Input/output statements are used to interact with the
user and perform necessary input/output operations in
C++
Conclusion

16. LIVE
CODING

17. QUESTIONS
& ANSWERS

18. CREDITS: This presentation template was created by Slidesgo,
including icons by Flaticon, and infographics & images by
Freepik
THANK YOU FOR
YOUR ATTENTION

19. CREDITS: This presentation template was created by Slidesgo,
including icons by Flaticon, and infographics & images by
Freepik
CREDITS
Guiding Lecturer
Dr. DO Thi Lien
Posts & Telecommunications Institute of Technology
Hanoi Campus
Please keep this slide for attribution

20. Our Team
B22DCDT178
• PHAM Nhu Linh
B22DCDT179
• VU Ngoc Linh
B22DCVT310
• TRINH Dieu Linh
B22DCVT343
• NGUYEN Cong
Minh
B22DCVT419
• BUI Khac Quan
B22DCVT333
• VU Duc Manh
B22DCVT450
• PHUNG Duc Tai
B22DCVT517
• PHUNG Tuan
Thanh