1. Basic Notions Review
what is a variable? value? address? memory location?
what is an identifier? variable name? keyword?
what is legal identifier? what identifiers are legal?
what are C-style, Camel Back-style identifiers?
what is variable type? what types have we studied?
what is variable declaration? where (in the program) is a variable declaration placed?
what is an assignment?
what is a stream? input stream? output stream? cout? cin?
what is an extraction/insertion operator?
what is an escape sequence?
what is an input token?

2. Types, Expressions, More on Assignment

3. int, double and Others
type is the kind of data that is stored in variables
int - whole numbers
double – numbers with fractions (called floating point)
since the storage is limited, fraction can contain only a limited number of digits (usually up to 14)
two ways to write a double number in C++
regular:
dot needs to be there
scientific or floating point (explicitly states mantissa and exponent):
5.89e5 .045E-4 5e+5 dot does not need to be there
mantissa is limited in size.
the largest allowable number differs for every architecture. Usually:
int - up to 32767
double - up to 10308
int or double (or any other type in C++) cannot contain a comma
other possible types are short, float and long double
in this course, use int

4. Character Type // asks for initials and outputs greeting
a variable stores a single character, e.g. ’a’, ’A’, ’%’, ’1’
declared char varName;
note that ’1’is also a character, not the same thing as numeric type 1
note also that ”1” is a string, not a character
// asks for initials and outputs greeting
#include <iostream>
main (){
char first, second;
cout << ”Enter your initials: ”;
cin >> first >> second;
cout << ”Hello ” << first << second << endl;
cout << ”pleased to meet you\n”; }

5. bool Type
bool (short for boolean) is used for branching and looping statements
a boolean variable can have only two values true or false
bool result;
result = true;
true and false are keywords and cannot be used as identifiers

6. Literal Constants an explicitly stated value is a literal constant
examples: ’a’ true
a literal constant has value and type
what are the types of the above constants?

7. Named Constants there are problems with using literal constants
9.8 does not give an idea as to what it means in the program
hard to modify if used in multiple places in program
named constant gives a name to a value; have to be declared:
const int windowCount = 5;
const double taxRate = 9.8;
style:
use named constants rather than literal constants
use constants rather than variables

8. Type Compatibility
as a rule you cannot store a value of one type in a variable of another type
trying to do it leads to type mismatch
int intvar;
intvar = 2.99;
compiler prints this:
warning: assignment to ’int' from ’double'
but still compiles the program discarding the fractional part
it is usually a bad idea (but some programmers do it) to store char values in variables of type int, bools can also be in int. Even though you compiler allows it, it obscures the meaning of the variables and should be avoided

9. Expressions expression is a mechanism of calculating new values
expression (similar to variable and constant) has type and value
simplest expression
literal constant
named constant
complex expression consists of operands joined by operators
operand – (sub) expression
operator – computes new values based on operands
arity - number of operands the operator uses
binary operator – two operands
unary operator – one operand

10. Binary Integer Operators
Operator Example
addition a+4 b+1
subtraction count
multiplication * 5*6 width*height
division / 12/3 4/5
remainder % 10% %4
for positive integers: if the integer division is not even, then the fractional part of the result is discarded: 12/5 produces 2
note that the fractional part is discarded and the result is never rounded up:
11/3 which should be (3.6666…) produces 3 not 4
the remainder can be used to “catch” the “missing” fraction 12%5 produces 2

11. Binary Double/Mixed Operators
Operator Example
addition
subtraction
multiplication * 5.4*2.3
division / / 5.0
there is no remainder operator with floating point
if there are integer and floating-point operands then the integers are first converted (by compiler) to floating-point operands and then the expression is evaluated: * is converted to * 2.0

12. Unary Operators, Precedence
precedence (order of execution) follows mathematical conventions: 1. Unary +, Binary *, /, % 3. Binary - and +
you can use () to change precedence:
(2+3)*2 changes default precedence
2 / is equivalent to (2 / 3) * 4 (-8) * % (7 % 4)

13. Whole Numbers in Division
when you divide int by int the result is int. It may be problematic in expression and the problem is hard to spot
the compiler would not complain
this program converts feet into miles. Is there anything wrong with it?
double totalPrice;
int feet;
cin >> feet;
totalPrice = 5000 * (feet/5280);

14. Assignment Conversions
if double expression is assigned to an integer variable, its fractional part is dropped
if int expression is assigned to a double variable, the expression is converted to double with zero fractional part
consider
double y = 2.7; int i = 15; int j = 10; i = y; // i is now 2 cout << i << endl; y = j; // y is now cout << y << endl;

15. Compound Assignment
compound assignment - joins assignment with another operator
syntax: variable operator = expression;
operator takes variable and expression as operands
computes the value, assigns it to variable
can be used for different types: int and double
shorthand for regular assignment
examples:
int i = 3; i += 4; // equivalent to i=i+4;
cout << i << endl; double a = 3.2; a *= 2.0; // equivalent to a=a*2.0; cout << a << endl;
examples of other compound assignments:
time /= rush_factor;
change %=100;
amount *= cnt1 + cnt2; // what is this equivalent to?

16. Increment and Decrement
increment – increase value by one, unary operator: ++
decrement – decrease value by one, unary operator: --
can be used
as a standalone statement ++k; or --k;
in an expression a = ++k + 5; or a = --k + 5;
two forms: prefix – preceding operand, and postfix/suffix – following operand
both forms can be used in standalone statements and expressions
no difference in standalone statements (stylistic preference)
in expressions,
in prefix form, the operation applies before value used in expression
int k=5;
a = ++k+5; // a is 11, k is 6
in suffix form, the operation applies after value is used in expression
a = k++ +5; // a is 10, k is 6
modern style: avoid postfix form (may be inefficient for complex types)

17. Increment and Decrement Example
int k;
k=4; ++k; // k is 5
k++; // k is 6 cout << k << endl; int i; i= k++; // i is 6, k is 7 cout << i << " " << k << endl; int j; j= ++k; // j is 8, k is 8 cout << j << " " << k << endl;

18. Initialization any declared variable contains a value
what is wrong with this code?
int desiredNumber;
desiredNumber=desiredNumber+5;
initialization – assigning a value to the variable at its declaration
two forms:
primary
int count=0, limit=10;
double distance=5.723, pi=3.14;
double step=limit/2.0;
alternative
int count(0), limit(10);
double distance(5.723), pi(3.14);
double step(limit/2.0);