1. Decisions, decisions, decisions
(it’s all in the bool!!)

2. Review – Boolean expressions
Boolean expressions are created using relational and logical operators
There are six relational operators –
==, >, <, >=, <=, !=
There are four logical operators (logical connectors) but we mostly use three
&&, ||, !, ^

3. Assume the following variable declarations:
int var1 = 10;
int var2 = 15;
bool result;
result = (var1 == 10) ; // is a true assertion so result gets a true (non-zero) value
Result = (var2 == 10); // is NOT a true assertion so result gets a false (0) value

4. Assume the following variable declarations:
int var1 = 10;
int var2 = 15;
bool result;
result = (var1 == 10) && (var1 != var2); // value of result ??
result = (var2 < var1) || (var2 != var1); // value of result??
result = (var2 > var1) ! (var2 == 25); // value of result??

5. Use of Boolean expressions to control operations
Decision structures
If (condition) {
true statements }
else
false statements

6. While structure while ( condition ) true statement; or {
true statements; }

7. Three Considerations when using Iterative control structures
Initialize the control variable – prior to entering the control structure the controlling variable MUST be initialized (given a starting value)
Test the controlling variable in the condition – if not sure use a constant for the limit then substitute a limiting variable
Modify the control variable within the controlled block of code – otherwise you may generate an “infinite loop”.

8. Some examples: int limit = 10; int ctr = 0; while( ctr < 10 ) {
cout << “counter = “ << ctr << endl;
ctr++; } OR
cout << “counter = “ << ctr++ << endl;

9. } while( ctr < limit );
The do – while – the condition (test) is after the execution of the block.
Example: do {
cout << “counter = “ << ctr << endl;
ctr++;
} while( ctr < limit );
Note the test is after the block and there is a semi-colon at the end of the condition.

10. The BIG 3 Summary and Comparison

11. And the switch() Used for multiple tests
Sometimes used instead of nested if – else
Uses an ordinal expression (variable) instead of a Boolean
Uses four terms (or words) – in no special order –
switch() - starts the switch structure and defines the ordinal statement
case – identifies the beginning of the programming sequence to be executed
break – terminates the execution of the local code block
default –executes if no match is found

12. switch() example switch(resp.at(0)) do {
cout << "Enter 1, 2, 3 or <E>xit: "; getline(cin,resp);
switch(resp.at(0))
{ // start of switch block
case '1':
cout << "A one was entered" << endl;
break;
case '2':
cout << "A two was typed in" << endl;
case '3':
cout << "A three was encountered" << endl;
case 'E':
case 'e':
default:
cout << "ERROR - Will Robinson" << endl;
cout << "Enter 1, 2, 3 or <E>xit: "; getline(cin, resp);
}while((resp.at(0)!= '1')&&(resp.at(0)!= '2')&&(resp.at(0)!= '3')&&(resp.at(0)!= 'E')&&(resp.at(0)!= 'e')); }
}while( (resp.at(0)!= 'E')&&(resp.at(0)!= 'e') );

13. Check out Rock, Paper, Scissors