1. Summary Two basic concepts: variables and assignments Basic types:
int, double, char (string), …
Some C++ practical issues:
division rule, operator precedence

2. Expression and statement
An expression has a value which is the result of some operation(s) on the associated operands.
4, x-y, 2-a-(b*c)
A statement is a sentence that acts as a command
it does not have a value
it always ends in a ‘;’
cin >> x;
x = 5;
int x;

3. Boolean type and expressions

4. Boolean type: bool
C++ contains a type (new!) named bool which can have one of two values
true (corresponding to non-zero value)
false (corresponding to zero value)
Boolean operators
Logical and: &&
Logical or: ||
Logical not: !
Examples
bool P = true; bool Q = false; bool R = true; bool S = P && Q; bool T = (!Q) || R; bool U = !(R && !Q);

5. Boolean expressions
Arithmetic expression: use arithmetic operators +,-,*,/, to produce a number as the final result
A Boolean expression has one of the two values: true or false
use relational operators <,>, ==, …
and boolean operators AND (&&), OR (||), NOT (!)

6. Using Relational Operators
Relational operators are used to compare two values
Math C++ Plain English
= == equals [example: if(a==b) ]
[ (a=b) means put the value of b into a ]
< < less than
 <= less than or equal to
> > greater than
 >= greater than or equal to
 != not equal to

7. Examples:
numberOfStudents < 200
10 > 20
20 * j == 10 + i

8. Using Boolean (logical) operators
Boolean operators can be used to form more complex conditional expressions
Logical AND operator  &&
Logical OR operator  ||
Logical NOT operator  !
Examples: (x>5) && (x<10)
(x>10) || (x<5)
!(x>5)
Warning!
& and | are also operators

9. Operator Precedence Answer: Which comes first? * / % + -
* / %
+ -
< <= >= >
== != =
Answer:

10. Summary of Operator Precedence
Precedence of operators (from highest to lowest)
Parentheses ( … )
Unary operators !
Multiplicative operators * / %
Additive operators + -
Relational ordering < <= >= >
Relational equality == !=
Logical and &&
Logical or ||
Assignment =
arithmetic
relational
logical

11. Example: 5 != 6 || 7 <= 3 (5 !=6) || (7 <= 3)
5 * == 13 && 12 < 19 || !false == 5 < 24

12. Flow control

13. Introduction Three program structures or constructs: Sequence
Statements in the given order
Conditional statement (branching)
Chooses between two (or more) sequences depending on some condition
if <condition exists> {
<do P> }
else {
<do Q>
Iteration statement (looping)
repetitively execute a given sequence
while <condition exists> {

14. Structured programming
Any program can be written as a sequence of three basic program structures!!!
1. sequences,
2. conditionals,
3. and iterations
Program
Structure 1
Program
Structure 3
Program
Structure 1
Program
Structure 2

15. The fundamental conditional if-else Statement
Choose between two alternative actions
depending on a test (on the values of variables).
Expression
Action1
Action2
true
false
Syntax
if (Expression)
Action1 else Action2
If Expression is true then execute Action1 otherwise execute Action2
Example
if(v == 0)
cout << "v is 0";
else
cout << "v is not 0";

16. It’s common in everyday life …?
if <it's sunny>{
<go to beach with sun block> }
else{
<go to beach with umbrella>

17. Example: Absolute Value (1st )
// program to read number & print its absolute value
#include <iostream>
using namespace std;
int main(){
int value;
int absvalue;
cout << "Enter integer: ";
cin >> value;
if (value < 0)
absvalue = -value;
else absvalue = value;
cout << "The absolute value is " << absvalue << endl;
return 0; }

18. When the action is more than one statement …
Put multiple action statements within braces
if <it's raining> {
<take umbrella>
<wear raincoat> }
else {
<take sunbathing stuff>

19. Example: Absolute Value (2nd)
// program to read number & print its absolute value
#include <iostream>
using namespace std;
int main(){
int value;
int absvalue; // absolute value
cout << "Enter integer: ";
cin >> value;
if (value < 0) {
absvalue = -value;
cout << "The input value is negative and its absolute value is " << absvalue << endl; }
else {
absvalue = value;
cout << "The input value is positive and its absolute value is " << absvalue << endl;
return 0;

20. Summary of the conditional if-else Statement
if (cond1)
B else C D
A A
B or C
D D =

21. Nested if-else Statements
Nested means that one complete statement is inside another
if cond1 { A;
if cond2 { B; }
else { C D

22. Example double score; cin >> score; if(score >= 90.0)
cout << "Grade = A" << endl;
else if(score >= 80.0)
cout << "Grade = B" << endl;
else if(score >= 70.0)
cout << "Grade = C" << endl;
else if(score >= 60.0)
cout << "Grade = D" << endl;
else
cout << "Grade = F" << endl;