This is a draft cheat sheet. It is a work in progress and is not finished yet.
Common Data Types
bool |
1 byte |
char |
1 byte |
int |
4 bytes (at least 2 bytes) |
long int |
4 bytes |
long long int |
8 bytes |
Header Files & Common Includes
#include <filename> |
#include <iostream> // cin & cout |
#include <fsream> // file streams |
#include <vector> // vectors |
#include <string> // strings |
Operators
a + b |
Addition |
a - b |
Subtraction |
a * b |
Multiplication |
a / b |
Division |
a % b |
Modulus |
a -= b |
(a-b) store in a |
a += b |
(a+b) store in a |
a /= b |
(a/b) store in a |
a *= b |
(a*b) store in a |
a++ |
(a+1) store in a |
a-- |
(a-1) store in a |
File IO
int main() {
// this makes a new file stream
fstream fileStream;
// open text.txt to write to
fileStream.open("test.txt", ios::out);
if (fileStream.is_open()) {
cout << "File opened!" << endl;
}
// write a line to the file
fileStream << "Hello!\n";
// must close to free the resource
fileStream.close();
return 0;
}
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Note that you must close the file before you can open a new new one. ios::out means you want to write to the file and ios::in means you want to read from the file. You write to a file stream the same way you write to cout.
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Classes
class some_name {
private:
int m_some_data1;
double m_some_data2;
public:
// this is a constructor
some_name(int a, double b) {
m_some_data1 = a;
m_some_data2 = b;
}
// getters
int get_some_data1() {
return m_some_data1;
}
double get_some_data2() {
return m_some_data2;
}
};
int main() {
/* makes a new object called name
which is of some_name type */
some_name name(0, 2.1);
return 0;
}
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Classes are just like user defined types like int or double. When an object is created it calls the constructor. The constructor is a function with the same name as the class.
Comparison Operators
a < b |
True if a is less than b |
a <= b |
True if a is less than or = to b |
a > b |
True if a is greater than b |
a >= b |
True if a is greater than or = to b |
a == b |
True if a equals b |
a && b |
True if a and b are true |
a || b |
True if a or b are true |
Note: If they do not meet the criteria to be true, they are false
Pointers
int main() {
int x = 3;
// & gets the memory address of x
int* pointer_to_x = &x;
/ pointers must be dereferenced with *
before they are accessed. */
*pointer = 5;
return 0;
}
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Note that pointers only hold a memory address. They cannot store anything else. In order to actually get the data at the address they must dereference it using the * operator.
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Pointers and References
int* ptr = mem_address; |
pointer definition |
int& ref = other_var; |
lvalue reference |
Note: pointers hold a single memory address that you can change while a reference holds a single unchangeable memory address.
Pointers
int main() {
int x = 3;
// & gets the memory address of x
int* pointer_to_x = &x;
/ pointers must be dereferenced with *
before they are accessed. */
*pointer = 5;
return 0;
}
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Note that pointers only hold a memory address. They cannot store anything else. In order to actually get the data at the address they must dereference it using the * operator.
Functions & Prototypes
void foo(); // prototype
void bar(int i); // prototype w/ params
void foo() { // foo definition
std::cout << "Foo function\n";
}
void bar(int i) { // bar definition
std::cout << "Bar: " << i << "\n";
}
int main() { // main definition
foo(); // calls foo function
bar(2); // calls bar with 2
return 0;
}
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All programs must have a main function. This is the first function that gets called. All functions except main() should have a prototype.
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