Switch statement/choice coding March 2, 2006
1
The
The switch
switch Statement and
Statement and
Programming Choice Structures
Programming Choice Structures
Larry Caretto
Computer Science 106
Computing in Engineering
and Science
March 2, 2006
2
Outline
• Review choice programming
– Statements (if, if-else, if-else-if)
– Conditions; relational and logical operators
– Type bool variables
– Nested if statements
• End-of-file tests
• Programming exercises
3
Review Choice (if statements)
• Three structures if, if-else, and if-else-if
• Based on statement if (<condition>)
• Condition used relational operators (<,
>, <=, >=, ==, !=) and logical operators
not(!) and(&&) or(||)
• Condition evaluates to true or false
• In if-else and if-else-if only one block of
code is executed
4
Review Type bool Variables
• Type bool variables have two possible
values: true and false
• Can be used to hold result of
expressions that give these values
• leapYear = year % 4 == 0 && ( year %
100 != 0 || year % 400 == 0 )
• Test bool variables in if statements and
use with logical operators
if ( leapYear && month == 2 ) days = 29;
5
Review DeMorgan’s Laws
• Have two bool expressions, a and b,
that can have values of true or false
• Combinations of conditions for a and b
satisfy both of the following
• !(a && b) = !a || !b
• !(a || b) = !a && !b
• Proved these using truth table
• Application to data validation follows
6
Review Data Validation
• Apply DeMorgan’s Law to Validation
badData = x < Min || x > Max;
goodData = x >= Min && x <= Max;
goodData = !badData;
goodData = !(x < Min || x > Max);
!(a|| b) = !a&& !b
goodData = !(x < Min) && !(x>Max)
goodData = x >= Min && x <= Max
