Ifs and Logic

1
Ifs and Logic

• Or
• Is it True or False.

2
Comparison operators

• A gt B is false (value of 0)
• D gt A is true (value of 1)
• 4 4 is true
• 5 lt 3 is false (value of 0)
• a ! A is true
• note true is the integer value 1 and false is
  the integer value 0

3
Logical operators

• is AND
• is OR
• are valuated before unless parentheses are
  used.

4
DeMorgans Law

• NOT (A AND B)(NOT A) OR (NOT B)
• NOT (A OR B)(NOT A) AND (NOT B)
• A NOT (NOT A)
• A AND B NOT( (NOT A) OR NOT(B))

5
Many forms of IF

• if (condition) single_statement
• if (condition)
  single1 else
  single2
• if (condition)
  many statements else
  many other statements

6
Good practice

• A block of code is fount between and
• Good practice is to code if else with blocks
• if (condition)
  many statements else
  many other statements
• This is true even if a block is empty.

7
else if

• if (condition)
  single1 else if (condition2)
  single2 else if (condition3) single
  3 else single4

8
Flow Charts

• Conventional
• Nassi-Schneiderman

9
switch

• switch(k)
• case 1
• cout ltlt Hiltltendl
• break
• case 4
• cout ltlt Good-byltlt endl
• break
• default
• cout ltltTry Againltltendl

10
switch components

• switch (expression)
• case value1
• many_statements
• break
• case values 2
• many_ statements

11

• break
• default
• many statements

12
To Do

• Modify the average of 3 exams to display a letter
  grade of A, B, C, D or F if the average is 90 or
  better 80 or better etc.
• Write a program that will input an integer and
  display odd if it is odd and even if it is
  even. This is a good program to use the
  division.