[C++] Chap 01 - C++ Basics

Variables

• Identifiers :
  • starts with letter or underscore(_), the rest characters must be letters, digits, underscore.
  • Case-sensitive
• Variables
  • A memory location to store data for a program
  • Must declare first
• Escape Sequences
  • “Extend” the character set
  • Uses Backslash (\)

Assignment rules / Compatibility

int variable;
intvariable = 2.99; 
// Type mismatch, but only integer part is stored.

• Some special cases are allowed

double doublevar;
doublevar = 2;

• Literals : considered “constants” (cannot be changed)
  • E.g) 2, 5.75, ‘Z’, “Hello World”

Arithmetic Precision

• “Highest-order operand” determines type of arithmetic “precision” performed

double x = 1/2/3.0/4; 
// Calculations are done "one-by-one" 1/2=0, 0/3.0=0.0, 0.0/4=0.0

Type casting

• Implicit (Automatic Type casting)
  • 17/5.5 → cast 17 to 17.0 ( “double” precision division is performed)
• Explicit type casting
  • (double)17/5.5

double a;
a=((double)9/5);
a=(9/(double)5);
a=(double)(9/5); // X
a=(9.0/5);

Increment, Decrement Operators

• Post / Pre Increment / Decrement
• Postfix : RValue, Increase value after line
• Prefix : Lvalue, Increase before execution

Console Input/Output

• cin , cout, cerr
• Must have the following lines :

#include <iostream>
using namespace std;

• cout
  • New lines in output : ‘\n’ or <<endl
  • Cascading is allowed : <<a << b
• cin
  • Extraction Operator >>
  • Must input “to a variable”
• Cout Formatting

cout.setf(ios::fixed);
cout.setf(ios::showpoint);
cout.precision(2); // shows two digits under decimal point

Comment

• // or /* */

Libraries

• C++ standard libraries : #include <LIBRARY_NAME>

Namespaces

• Collection of name definitions
• using namespace std;