This repository contains personal notes on learning the C++ programming language. It covers a range of topics, including basic syntax, data types, and common functions and libraries. The notes are intended to serve as a reference for anyone looking to learn or brush up on their C++ skills.
# for Fedora
dnf install gcc-c++ gdb clang-tools-extrabool x = true; // 1 byte, values 0, 1
char a = 'a'; // 1 byte, values -127 to 127 or 0 to 255, usually 8 bit character
unsigned char b = 0xff; // 1 byte, values 0 to 255
signed char c = -1; // 1 byte, values -127 to 127
int d = 1234; // 4 bytes, values -2147483648 to 2147483647
unsigned int e = 1; // 4 bytes, values 0 to 4294967295
signed int f = -127; // 4 bytes, values -2147483648 to 2147483647
short int g = -256; // 2 bytes, values -32768 to 32767
unsigned short int h = 65'535; // 2 bytes, values 0 to 65,535
signed short int i = 32'767; // 2 bytes, values -32768 to 32767
long int j = 0xffffffffffffffL; // 8 bytes, values -9223372036854775808 to 9223372036854775807
signed long int k = -0xffffffffffffff; // 8 bytes, values -9223372036854775808 to 9223372036854775807
unsigned long int l = 0xffffffffffffffffUL; // 8 bytes, values 0 to 18446744073709551615
long long int m = -0xfffffffffffffff; // 8 bytes, values -(2^63) to (2^63)-1
unsigned long long int n = 0xfffffffffffffff; // 8 bytes, 0 to 18,446,744,073,709,551,615
float o = 2.5; // 4 bytes, single precision real (never unsigned)
double p = 3.14; // 8 bytes, double precision real (never unsigned)
long double q = 6.62607015e-34; // 12 bytes
wchar_t r = L'ם'; // 2 or 4 bytes, values 1 wide character
int8_t s = 0x7f; // 1 byte, values -127 to 127
int16_t t = 0x7fff; // 2 bytes, values -32768 to 32767
int32_t u = 0x7fffffff; // 4 bytes, values -2147483648 to 2147483647
int64_t v = 0x7fffffffffffffff; // 8 bytes, values -9223372036854775808 to 9223372036854775807
uint8_t us = 0xff; // 1 byte, values 0 to 255
uint16_t ut = 0xffff; // 2 bytes, values 0 to 65,535
uint32_t uu = 0xffffffff; // 4 bytes, values 0 to 4294967295
uint64_t uv = 0xffffffffffffffff; // 8 bytes, values 0 to 18446744073709551615
// Comment to end of line
/* Multi-line comment */
#include <stdio.h> // Insert standard header file
#include "myfile.h" // Insert file in current directory
#define X some text // Replace X with some text
#define F(a,b) a+b // Replace F(1,2) with 1+2
#define X \
some text // Multiline definition
#undef X // Remove definition
#if defined(X) // Conditional compilation (#ifdef X)
#else // Optional (#ifndef X or #if !defined(X))
#endif // Required after #if, #ifdef255, 0377, 0xff // Integers (decimal, octal, hex)
2147483647L, 0x7fffffffl // Long (32-bit) integers
123.0, 1.23e2 // double (real) numbers
'a', '\141', '\x61' // Character (literal, octal, hex)
'\n', '\\', '\'', '\"' // Newline, backslash, single quote, double quote
"string\n" // Array of characters ending with newline and \0
"hello" "world" // Concatenated strings
true, false // bool constants 1 and 0
nullptr // Pointer type with the address of 0int x; // Declare x to be an integer (value undefined)
int x=255; // Declare and initialize x to 255
short s; long l; // Usually 16 or 32 bit integer (int may be either)
char c='a'; // Usually 8 bit character
unsigned char u=255;
signed char s=-1; // char might be either
unsigned long x = 0xffffffffL; // short, int, long are signed
float f; double d; // Single or double precision real (never unsigned)
bool b=true; // true or false, may also use int (1 or 0)
int a, b, c; // Multiple declarations
int a[10]; // Array of 10 ints (a[0] through a[9])
int a[]={0,1,2}; // Initialized array (or a[3]={0,1,2}; )
int a[2][2]={{1,2},{4,5}}; // Array of array of ints
char s[]="hello"; // String (6 elements including '\0')
std::string s = "Hello" // Creates string object with value "Hello"
std::string s = R"(Hello
World)"; // Creates string object with value "Hello\nWorld"
int* p; // p is a pointer to (address of) int
char* s="hello"; // s points to unnamed array containing "hello"
void* p=nullptr; // Address of untyped memory (nullptr is 0)
int& r=x; // r is a reference to (alias of) int x
enum weekend {SAT,SUN}; // weekend is a type with values SAT and SUN
enum weekend day; // day is a variable of type weekend
enum weekend{SAT=0,SUN=1}; // Explicit representation as int
enum {SAT,SUN} day; // Anonymous enum
enum class Color {Red,Blue}; // Color is a strict type with values Red and Blue
Color x = Color::Red; // Assign Color x to red
typedef String char*; // String s; means char* s;
const int c=3; // Constants must be initialized, cannot assign to
const int* p=a; // Contents of p (elements of a) are constant
int* const p=a; // p (but not contents) are constant
const int* const p=a; // Both p and its contents are constant
const int& cr=x; // cr cannot be assigned to change x
int8_t,uint8_t,int16_t,
uint16_t,int32_t,uint32_t,
int64_t,uint64_t // Fixed length standard types
auto it = m.begin(); // Declares it to the result of m.begin()
auto const param = config["param"]; // Declares it to the const result
auto& s = singleton::instance(); // Declares it to a reference of the resultint x; // Auto (memory exists only while in scope)
static int x; // Global lifetime even if local scope
extern int x; // Information only, declared elsewherex=y; // Every expression is a statement
int x; // Declarations are statements
; // Empty statement
{ // A block is a single statement
int x; // Scope of x is from declaration to end of block
}
if (x) a; // If x is true (not 0), evaluate a
else if (y) b; // If not x and y (optional, may be repeated)
else c; // If not x and not y (optional)
while (x) a; // Repeat 0 or more times while x is true
for (x; y; z) a; // Equivalent to: x; while(y) {a; z;}
for (x : y) a; // Range-based for loop e.g.
// for (auto& x in someList) x.y();
do a; while (x); // Equivalent to: a; while(x) a;
switch (x) { // x must be int
case X1: a; // If x == X1 (must be a const), jump here
case X2: b; // Else if x == X2, jump here
default: c; // Else jump here (optional)
}
break; // Jump out of while, do, or for loop, or switch
continue; // Jump to bottom of while, do, or for loop
return x; // Return x from function to caller
try { a; }
catch (T t) { b; } // If a throws a T, then jump here
catch (...) { c; } // If a throws something else, jump hereint f(int x, int y); // f is a function taking 2 ints and returning int
void f(); // f is a procedure taking no arguments
void f(int a=0); // f() is equivalent to f(0)
f(); // Default return type is int
inline f(); // Optimize for speed
f() { statements; } // Function definition (must be global)
T operator+(T x, T y); // a+b (if type T) calls operator+(a, b)
T operator-(T x); // -a calls function operator-(a)
T operator++(int); // postfix ++ or -- (parameter ignored)
extern "C" {void f();} // f() was compiled in CT::X // Name X defined in class T
N::X // Name X defined in namespace N
::X // Global name X
t.x // Member x of struct or class t
p-> x // Member x of struct or class pointed to by p
a[i] // i'th element of array a
f(x,y) // Call to function f with arguments x and y
T(x,y) // Object of class T initialized with x and y
x++ // Add 1 to x, evaluates to original x (postfix)
x-- // Subtract 1 from x, evaluates to original x
typeid(x) // Type of x
typeid(T) // Equals typeid(x) if x is a T
dynamic_cast< T>(x) // Converts x to a T, checked at run time.
static_cast< T>(x) // Converts x to a T, not checked
reinterpret_cast< T>(x) // Interpret bits of x as a T
const_cast< T>(x) // Converts x to same type T but not const
sizeof x // Number of bytes used to represent object x
sizeof(T) // Number of bytes to represent type T
++x // Add 1 to x, evaluates to new value (prefix)
--x // Subtract 1 from x, evaluates to new value
~x // Bitwise complement of x
!x // true if x is 0, else false (1 or 0 in C)
-x // Unary minus
+x // Unary plus (default)
&x // Address of x
*p // Contents of address p (*&x equals x)
new T // Address of newly allocated T object
new T(x, y) // Address of a T initialized with x, y
new T[x] // Address of allocated n-element array of T
delete p // Destroy and free object at address p
delete[] p // Destroy and free array of objects at p
(T) x // Convert x to T (obsolete, use .._cast<T>(x))
x * y // Multiply
x / y // Divide (integers round toward 0)
x % y // Modulo (result has sign of x)
x + y // Add, or \&x[y]
x - y // Subtract, or number of elements from *x to *y
x << y // x shifted y bits to left (x * pow(2, y))
x >> y // x shifted y bits to right (x / pow(2, y))
x < y // Less than
x <= y // Less than or equal to
x > y // Greater than
x >= y // Greater than or equal to
x & y // Bitwise and (3 & 6 is 2)
x ^ y // Bitwise exclusive or (3 ^ 6 is 5)
x | y // Bitwise or (3 | 6 is 7)
x && y // x and then y (evaluates y only if x (not 0))
x || y // x or else y (evaluates y only if x is false (0))
x = y // Assign y to x, returns new value of x
x += y // x = x + y, also -= *= /= <<= >>= &= |= ^=
x ? y : z // y if x is true (nonzero), else z
throw x // Throw exception, aborts if not caught
x , y // evaluates x and y, returns y (seldom used)class T { // A new type
private: // Section accessible only to T's member functions
protected: // Also accessible to classes derived from T
public: // Accessible to all
int x; // Member data
void f(); // Member function
void g() {return;} // Inline member function
void h() const; // Does not modify any data members
int operator+(int y); // t+y means t.operator+(y)
int operator-(); // -t means t.operator-()
T(): x(1) {} // Constructor with initialization list
T(const T& t): x(t.x) {} // Copy constructor
T& operator=(const T& t)
{x=t.x; return *this; } // Assignment operator
~T(); // Destructor (automatic cleanup routine)
explicit T(int a); // Allow t=T(3) but not t=3
T(float x): T((int)x) {} // Delegate constructor to T(int)
operator int() const
{return x;} // Allows int(t)
friend void i(); // Global function i() has private access
friend class U; // Members of class U have private access
static int y; // Data shared by all T objects
static void l(); // Shared code. May access y but not x
class Z {}; // Nested class T::Z
typedef int V; // T::V means int
};
void T::f() { // Code for member function f of class T
this->x = x;} // this is address of self (means x=x;)
int T::y = 2; // Initialization of static member (required)
T::l(); // Call to static member
T t; // Create object t implicit call constructor
t.f(); // Call method f on object t
struct T { // Equivalent to: class T { public:
virtual void i(); // May be overridden at run time by derived class
virtual void g()=0; }; // Must be overridden (pure virtual)
class U: public T { // Derived class U inherits all members of base T
public:
void g(int) override; }; // Override method g
class V: private T {}; // Inherited members of T become private
class W: public T, public U {}; // Multiple inheritance
class X: public virtual T {}; // Classes derived from X have base T directlyAll classes have a default copy constructor, assignment operator, and destructor, which perform the corresponding operations on each data member and each base class as shown above. There is also a default no-argument constructor (required to create arrays) if the class has no constructors. Constructors, assignment, and destructors do not inherit.
template <class T> T f(T t); // Overload f for all types
template <class T> class X { // Class with type parameter T
X(T t); }; // A constructor
template <class T> X<T>::X(T t) {}
// Definition of constructor
X<int> x(3); // An object of type "X of int"
template <class T, class U=T, int n=0>
// Template with default parametersnamespace N {class T {};} // Hide name T
N::T t; // Use name T in namespace N
using namespace N; // Make T visible without N::Dynamic memory management.
#include <memory> // Include memory (std namespace)
shared_ptr<int> x; // Empty shared_ptr to a integer on heap. Uses reference counting for cleaning up objects.
x = make_shared<int>(12); // Allocate value 12 on heap
shared_ptr<int> y = x; // Copy shared_ptr, implicit changes reference count to 2.
cout << *y; // Dereference y to print '12'
if (y.get() == x.get()) { // Raw pointers (here x == y)
cout << "Same";
}
y.reset(); // Eliminate one owner of object
if (y.get() != x.get()) {
cout << "Different";
}
if (y == nullptr) { // Can compare against nullptr (here returns true)
cout << "Empty";
}
y = make_shared<int>(15); // Assign new value
cout << *y; // Dereference x to print '15'
cout << *x; // Dereference x to print '12'
weak_ptr<int> w; // Create empty weak pointer
w = y; // w has weak reference to y.
if (shared_ptr<int> s = w.lock()) { // Has to be copied into a shared_ptr before usage
cout << *s;
}
unique_ptr<int> z; // Create empty unique pointers
unique_ptr<int> q;
z = make_unique<int>(16); // Allocate int (16) on heap. Only one reference allowed.
q = move(z); // Move reference from z to q.
if (z == nullptr){
cout << "Z null";
}
cout << *q;
shared_ptr<B> r;
r = dynamic_pointer_cast<B>(t); // Converts t to a shared_ptr<B>Variable sized character array.
#include <string> // Include string (std namespace)
string s1, s2="hello"; // Create strings
s1.size(), s2.size(); // Number of characters: 0, 5
s1 += s2 + ' ' + "world"; // Concatenation
s1 == "hello world" // Comparison, also <, >, !=, etc.
s1[0]; // 'h'
s1.substr(m, n); // Substring of size n starting at s1[m]
s1.c_str(); // Convert to const char*
s1 = to_string(12.05); // Converts number to string
getline(cin, s); // Read line ending in '\n'
Fixed-size contiguous array with overhead-free random access.
Excels in fast traversal and good for linear searches.
size has to be a constant expression (= known at compile time).
Does not support size-changing operations (resize, insert, erase, …).
Potentially slow if element type has high copy/assignment cost (reordering elements requires copying/moving them)
#include <array> // Include vector (std namespace)
std::array<int,6> a {4,8,15,16,23,42};
// Create array with values 4,8,15,16..
a.size(); // Number of elements (6)
a[0]; // 4
a[3]; // 16
a.front(); // 4
a.back(); // 42
Dynamic contiguous array/stack with built in memory allocation. Amortized O(1) growth strategy. C++'s default container.
#include <vector> // Include vector (std namespace)
vector<int> a(10); // a[0]..a[9] are int (default size is 0)
vector<int> b{1,2,3}; // Create vector with values 1,2,3
a.size(); // Number of elements (10)
a.push_back(3); // Increase size to 11, a[10]=3
a.back()=4; // a[10]=4;
a.pop_back(); // Decrease size by 1
a.front(); // a[0];
a[20]=1; // Crash: not bounds checked
a.at(20)=1; // Like a[20] but throws out_of_range()
for (int& p : a)
p=0; // C++11: Set all elements of a to 0
for (vector<int>::iterator p=a.begin(); p!=a.end(); ++p)
*p=0; // C++03: Set all elements of a to 0
vector<int> b(a.begin(), a.end()); // b is copy of a
vector<T> c(n, x); // c[0]..c[n-1] init to x
T d[10]; vector<T> e(d, d+10); // e is initialized from d
Constant-time random access (extremely small overhead). Good insertion and deletion performance at both ends.
deque<T> is like vector<T>, but also supports:
#include <deque> // Include deque (std namespace)
a.push_front(x); // Puts x at a[0], shifts elements toward back
a.pop_front(); // Removes a[0], shifts toward front
Doubly-linked list; O(1) insert, erase & splicing; in practice often slower than vector. Restructuring operations don't require elements to be moved/copied (good for storing large objects with high copy/assignment cost). Constant-time splicing (of complete lists).
#include <list> // Include list (std namespace)
std::list<int> l {3};
l.push_back(2); // Adds a new element ‘2’ at the end of the list
l.push_front(4); // Adds a new element ‘4’ at the beginning of the list
l.splice(begin(l)+1,
list<int>{8, 4, 7}); // Used to transfer elements from one list to another
l.reverse(); // Reverses the list
l.sort(); // Sorts the list in increasing order
l.unique(); // Removes all duplicate consecutive elements from the list
]
Singly-linked list; O(1) insert, erase & splicing; needs less memory than list; in practice often slower than vector.
#include <forward_list> // Include list (std namespace)
std::forward_list<int> l {23,42,4}; // Create list with values 23,42,4
l.insert_after(begin(l), 5); // Puts values into second position overwriting 42
l.insert_after(before_begin(l), 88); // Puts value in the first position overwriting 23
l.erase_after(begin(l)); // Removes second element#include <utility> // Include utility (std namespace)
pair<string, int> a("hello", 7); // A 2-element struct
a.first; // "hello"
a.second; // 7
Associative array usually implemented as binary search trees - avg. time complexity: O(log n).
#include <map> // Include map (std namespace)
map<string, int> a; // Map from string to int
a["hello"] = 3; // Add or replace element a["hello"]
for (auto& p:a)
cout << p.first << p.second; // Prints hello, 3
a.size(); // 1
Associative array usually implemented as hash table - avg. time complexity: O(1)
#include <unordered_map> // Include map (std namespace)
unordered_map<string, int> a; // Map from string to int
a["hello"] = 3; // Add or replace element a["hello"]
for (auto& p:a)
cout << p.first << p.second; // Prints hello, 3
a.size(); // 1
Store unique elements - usually implemented as binary search trees - avg. time complexity: O(log n)
#include <set> // Include set (std namespace)
set<int> s; // Set of integers
s.insert(123); // Add element to set
if (s.find(123) != s.end()) // Search for an element
s.erase(123);
cout << s.size(); // Number of elements in set
Store unique elements - usually implemented as a hash set - avg. time complexity: O(1)
#include <unordered_set> // Include set (std namespace)
unordered_set<int> s; // Set of integers
s.insert(123); // Add element to set
if (s.find(123) != s.end()) // Search for an element
s.erase(123);
cout << s.size(); // Number of elements in setFloating point math.
#include <cmath> // Include cmath (std namespace)
sin(x); cos(x); tan(x); // Trig functions, x (double) is in radians
asin(x); acos(x); atan(x); // Inverses
atan2(y, x); // atan(y/x)
sinh(x); cosh(x); tanh(x); // Hyperbolic sin, cos, tan functions
exp(x); log(x); log10(x); // e to the x, log base e, log base 10
pow(x, y); sqrt(x); // x to the y, square root
ceil(x); floor(x); // Round up or down (as a double)
fabs(x); fmod(x, y); // Absolute value, x mod yDebugging aid.
#include <cassert> // Include iostream (std namespace)
assert(e); // If e is false, print message and abort
#define NDEBUG // (before #include <assert.h>), turn off assertReplaces stdio.h.
#include <iostream> // Include iostream (std namespace)
cin >> x >> y; // Read words x and y (any type) from stdin
cout << "x=" << 3 << endl; // Write line to stdout
cerr << x << y << flush; // Write to stderr and flush
c = cin.get(); // c = getchar();
cin.get(c); // Read char
cin.getline(s, n, '\n'); // Read line into char s[n] to '\n' (default)
if (cin) // Good state (not EOF)?
// To read/write any type T:
istream& operator>>(istream& i, T& x) {i >> ...; x=...; return i;}
ostream& operator<<(ostream& o, const T& x) {return o << ...;}File I/O works like cin, cout as above.
#include <fstream> // Include filestream (std namespace)
ifstream f1("filename"); // Open text file for reading
if (f1) // Test if open and input available
f1 >> x; // Read object from file
f1.get(s); // Read char or line
f1.getline(s, n); // Read line into string s[n]
ofstream f2("filename"); // Open file for writing
if (f2) f2 << x; // Write to fileA collection of 60 algorithms on sequences with iterators
#include <algorithm> // Include algorithm (std namespace)
min(x, y); max(x, y); // Smaller/larger of x, y (any type defining <)
swap(x, y); // Exchange values of variables x and y
sort(a, a+n); // Sort array a[0]..a[n-1] by <
sort(a.begin(), a.end()); // Sort vector or deque
reverse(a.begin(), a.end()); // Reverse vector or dequeTime related library.
#include <chrono> // Include chrono
using namespace std::chrono; // Use namespace
auto from = // Get current time_point
high_resolution_clock::now();
// ... do some work
auto to = // Get current time_point
high_resolution_clock::now();
using ms = // Define ms as floating point duration
duration<float, milliseconds::period>;
// Compute duration in milliseconds
cout << duration_cast<ms>(to - from)
.count() << "ms";Multi-threading library.
#include <thread> // Include thread
unsigned c =
hardware_concurrency(); // Hardware threads (or 0 for unknown)
auto lambdaFn = [](){ // Lambda function used for thread body
cout << "Hello multithreading";
};
thread t(lambdaFn); // Create and run thread with lambda
t.join(); // Wait for t finishes
// --- shared resource example ---
mutex mut; // Mutex for synchronization
condition_variable cond; // Shared condition variable
const char* sharedMes // Shared resource
= nullptr;
auto pingPongFn = // thread body (lambda). Print someone else's message
[&](const char* mes){
while (true){
unique_lock<mutex> lock(mut);// locks the mutex
do {
cond.wait(lock, [&](){ // wait for condition to be true (unlocks while waiting which allows other threads to modify)
return sharedMes != mes; // statement for when to continue
});
} while (sharedMes == mes); // prevents spurious wakeup
cout << sharedMes << endl;
sharedMes = mes;
lock.unlock(); // no need to have lock on notify
cond.notify_all(); // notify all condition has changed
}
};
sharedMes = "ping";
thread t1(pingPongFn, sharedMes); // start example with 3 concurrent threads
thread t2(pingPongFn, "pong");
thread t3(pingPongFn, "boing");Thread support library.
#include <future> // Include future
function<int(int)> fib = // Create lambda function
[&](int i){
if (i <= 1){
return 1;
}
return fib(i-1)
+ fib(i-2);
};
future<int> fut = // result of async function
async(launch::async, fib, 4); // start async function in other thread
// do some other work
cout << fut.get(); // get result of async function. Wait if needed.- 📺️ C++ Tutorial for Beginners - Learn C++ in 1 Hour
- Using C++ on Linux in VS Code
- Visual Studio Code C++ December 2021 Update: clang-tidy
- Google C++ Style Guide
- Google C++ Style Guide [with code highlight]
- Bjarne Stroustrup's C++ Style and Technique FAQ
- STL Algorithms
- mortennobel/cpp-Cheat sheet
- C++ Cheat Sheets & Infographics
- CMake Tutorial
- 📑 C++ Beginner's Guide