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Cheat Sheet

C++ All-In-One For Dummies

From C++ All-in-One For Dummies, 3rd Edition by John Paul Mueller

C++ is a popular programming language because it’s powerful, fast, easy to use, standardized, and more. Whether you are new to C++ programming or an advanced user, check out the following information on C++ mistakes, header files, and syntax. All information pertains to Windows, Mac, and Linux computers.

The 10 Most Common C++ Mistakes

Although many C++ programmers take measures to prevent bugs, mistakes still slip through. This list of the ten most common mistakes while writing C++ code can help both new and veteran programmers:

  1. You forgot to declare the variable.

  2. You used the wrong uppercase and lowercase letters; for example, you typed Main when you meant main.

  3. You used one equal sign (=) when you were supposed to use two (==), either in an if statement or in a for loop.

  4. You forgot #include <iostream> or using namespace std;.

  5. You dropped the laptop in the swimming pool.

  6. You forgot to call new and just started using the pointer anyway.

  7. You forgot the word public: in your classes so everything turned up private.

  8. You let the dog eat the remote.

  9. You forgot to type the parentheses when calling a function that takes no parameters.

  10. You forgot a semicolon, probably at the end of a class declaration.

The Usual C++ Header Files

In C++, a header file holds forward declarations of identifiers. Here are some of the most common C++ header files that you’ll be using, along with their correct spellings. These aren’t by any means all of them, but they are the most common:

  • Include <string> if you’re going to be using the string class.

  • Include <iostream> when you want to use cout and cin.

  • Include <fstream> when you want to read or write files.

  • Include <iomanip> if you want advanced manipulator usage in your streams.

  • Include <stdlib.h> for general operations, including system(“PAUSE”).

C++ Syntax that You May Have Forgotten

Remembering a bunch of C++ syntax can make you "loopy." The following samples show the syntax of some of the more easily forgotten C++ situations: a for loop, a while loop, and a switch statement; a class and the code for a member function; a base class and a derived class; a function, function pointer type, and pointer to the function; and a class template and then a class based on the template.

Here’s a for loop:

int i;
for (i=0; i<10; i++) {
    cout << i << endl;

Here’s a while loop that counts from 10 down to 1:

int i = 10;
while (i > 0) {
    cout << i << endl;

And here’s a switch statement:

switch (x) {
case 1:
    cout << “1” << endl;
case 2:
    cout << “2” << endl;
    cout << “Something else” << endl;

Here’s a class and the code for a member function:

class MyClass {
    int x;
    void MyFunction(int y);
void MyClass::MyFunction(int y) {
    x = y;

Here’s a base class and a derived class:

class MyBase {
   // derived classes can
   // not access this
   int a;   
   // derived classes can 
   // access this
   int b;   
class Derived : public MyBase {
    void test() {
        b = 10;

Here’s a function, a function pointer type, and a pointer to the function:

int function(char x) {
    return (int)x;
typedef int (* funcptr)(char);
funcptr MyPtr = function;

And here’s a class template and then a class based on the template:

template <typename T>
class MyTemplate {
    T a;
MyTemplate<int> X;
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