Basic syntax and functions from the C++ programming language.
Boilerplate
#include <iostream>
using namespace std;
int main() {
cout <<"Hello World";
return 0;
}
cout << It prints output on the screen
cout << "This is C++ Programming";
cin >> It takes input from the user
cin >> variable_name
Data types
The data type is the type of data
Character type
Typically a single octet(one byte). It is an integer type
char variable_name;
Integer type
The most natural size of integer for the machine
int variable_name;
Float type
A single-precision floating-point value
float variable_name;
Double type
A double-precision floating-point value
double variable_name;
Void type
Represents the absence of the type
void
Boolean type
bool
Escape Sequences
It is a sequence of characters starting with a backslash, and it doesn't represent itself when used inside string literal.
Alarm or Beep
It produces a beep sound
\a
Backspace
It adds a backspace
\b
Form feed
\f
Newline
Newline Character
\n
Carriage return
\r
Tab
It gives a tab space
\t
Backslash
It adds a backslash
\\
Single quote
It adds a single quotation mark
\'
Question mark
It adds a question mark
\?
Octal No.
It represents the value of an octal number
\nnn
Hexadecimal No.
It represents the value of a hexadecimal number
\xhh
Null
The null character is usually used to terminate a string
\0
Comments
A comment is a code that is not executed by the compiler, and the programmer uses it to keep track of the code.
Single line comment
// It's a single line comment
Multi-line comment
/* It's a
multi-line
comment
*/
Strings
It is a collection of characters surrounded by double quotes
Declaring String // Include the string library
#include <string>
String variable
string variable1 = "Hello World";
append function
It is used to concatenate two strings
string fullName = firstName.append(lastName);
cout << fullName;
length function It returns the length of the string
cout << "The length of the string is: " << variable1.length();
Accessing and changing string characters
string variable1 = "Hello World";
variable1[1] = 'i';
cout << variable1;
Maths
C++ provides some built-in math functions that help the programmer to perform mathematical operations efficiently.
max function
It returns the larger value among the two
string firstName = "Harry ";
string lastName = "Potter";
string variable1 = "Harry Potter";
cout << max(25, 140);
min function It returns the smaller value among the two
cout << min(55, 50);
sqrt function It returns the square root of a supplied number
#include <cmath>
cout << sqrt(144);
ceil function It returns the value of x rounded up to its nearest integer
ceil(x)
floor function It returns the value of x rounded down to its nearest integer
floor(x)
pow function It returns the value of x to the power of y
pow(x, y)
Decision Making Instructions Conditional statements are used to perform operations based on some condition. If Statement
if (condition) {
// This block of code will get executed if the condition is True
}
If-else Statement
if (condition) {
// If condition is True then this block will get executed
} else {
// If condition is False then this block will get executed
}
if else-if Statement
if (condition) {
// Statements;
}
else if (condition){
// Statements;
}
else{
// Statements
}
Ternary Operator It is shorthand of an if-else statement.
variable = (condition) ? expressionTrue : expressionFalse;
Switch Case Statement It allows a variable to be tested for equality against a list of values (cases).
switch (expression)
{
case constant-expression:
statement1;
statement2;
break;
case constant-expression:
statement;
break;
...
default:
statement;
}
Iterative Statements
Iterative statements facilitate programmers to execute any block of code lines repeatedly and can be controlled as per conditions added by the programmer.
while Loop It iterates the block of code as long as a specified condition is True
while (/* condition */)
{
/* code block to be executed */
}
do-while loop It is an exit-controlled loop. It is very similar to the while loop with one difference, i.e., the body of the do-while loop is executed at least once even if the condition is False
do
{
/* code */
} while (/* condition */);
for loop It is used to iterate the statements or a part of the program several times. It is frequently used to traverse the data structures like the array and linked list.
for (int i = 0; i < count; i++)
{
/* code */
}
Break Statement break keyword inside the loop is used to terminate the loop
break;
Continue Statement continue keyword skips the rest of the current iteration of the loop and returns to the starting point of the loop
continue;
References
Reference is an alias for an already existing variable. Once it is initialized to a variable, it cannot be changed to refer to another variable. So, it's a const pointer. Creating References
string var1 = "Value1"; // var1 variable
string &var2 = var1; // reference to var1
Pointers Pointer is a variable that holds the memory address of another variable Declaration
datatype *var_name;
var_name = &variable2;
Functions & Recursion
Functions are used to divide an extensive program into smaller pieces. It can be called multiple times to provide reusability and modularity to the C program. Function Definition
return_type function_name(data_type parameter...){
//code to be executed
}
Function Call
function_name(arguments);
Recursion
Recursion is when a function calls a copy of itself to work on a minor problem. And the function that calls itself is known as the Recursive function.
void recurse()
{
... .. ...
recurse();
... .. ...
}
Object-Oriented Programming
It is a programming approach that primarily focuses on using objects and classes. The objects can be any real-world entity.
class
class Class_name {
public: // Access specifier
// fields
// functions
// blocks
};
object
Class_name ObjectName;
Constructors
It is a special method that is called automatically as soon as the object is created.
class className { // The class
public: // Access specifier
className() { // Constructor
}
};
int main() {
className obj_name;
return 0;
}
Encapsulation
Data encapsulation is a mechanism of bundling the data, and the functions that use them and data abstraction is a mechanism of exposing only the interfaces and hiding the implementation details from the user.
#include<iostream>
using namespace std;
class ExampleEncap{
private:
/* Since we have marked these data members private,
* any entity outside this class cannot access these
* data members directly, they have to use getter and
* setter functions.
*/
int num;
char ch;
public:
/* Getter functions to get the value of data members.
* Since these functions are public, they can be accessed
* outside the class, thus provide the access to data members
* through them
*/
int getNum() const {
return num;
}
char getCh() const {
return ch;
cout << "Harry Potter";
}
/* Setter functions, they are called for assigning the values
* to the private data members.
*/
void setNum(int num) {
this->num = num;
}
void setCh(char ch) {
this->ch = ch;
}
};
int main(){
ExampleEncap obj;
obj.setNum(100);
obj.setCh('A');
cout<<obj.getNum()<<endl;
cout<<obj.getCh()<<endl;
return 0;
}
File Handling
File handling refers to reading or writing data from files. C provides some functions that allow us to manipulate data in the files.
Creating and writing to a text file
#include <iostream>
#include <fstream>
using namespace std;
int main() {
// Create and open a text file
ofstream MyFile("filename.txt");
// Write to the file
MyFile << "File Handling in C++";
// Close the file
MyFile.close();
}
Reading the file
It allows us to read the file line by line
getline()
Opening a File
It opens a file in the C++ program
void open(const char* file_name,ios::openmode mode);
OPEN MODES
in
Opens the file to read(default for ifstream)
fs.open ("test.txt", std::fstream::in)
out
Opens the file to write(default for ofstream)
fs.open ("test.txt", std::fstream::out)
binary Opens the file in binary mode
fs.open ("test.txt", std::fstream::binary)
app Opens the file and appends all the outputs at the end
fs.open ("test.txt", std::fstream::app)
ate
Opens the file and moves the control to the end of the file
fs.open ("test.txt", std::fstream::ate)
trunc
Removes the data in the existing file
fs.open ("test.txt", std::fstream::trunc)
nocreate
Opens the file only if it already exists
fs.open ("test.txt", std::fstream::nocreate)
noreplace
Opens the file only if it does not already exist
fs.open ("test.txt", std::fstream::noreplace)
Closing a file
It closes the file
myfile.close()
Exception Handling
An exception is an unusual condition that results in an interruption in the flow of the program. try and catch block
A basic try-catch block in python. When the try block throws an error, the control goes to the except for block
try {
// code to try
throw exception; // If a problem arises, then throw an exception
}
catch () {
// Block of code to handle errors
}