5. The IF Statement

Question 1

control structures: a computer can proceed

Answer 1

• in a sequence
• selectively (branch) - making a choice
• repetitively (iteratively) - looping

Question 2

If-Else statement

Answer 2

allows you to do diff things depending on a condition

Question 3

condition

Answer 3

an expression whose value is true or false

Question 4

symbols for conditions

Answer 4

>
<
== 
!=
>=
<= 
!> 
etc

Question 5

note on ==

Answer 5

cannot use = for conditions, as = is used for assigning

Question 6

combining else and if

Answer 6

if ..
else if…
else ..

Question 7

logical (boolean) expressions)

Answer 7

data type bool has logical values true and false

Question 8

bool, true, false

Answer 8

reserved words

Question 9

identifier true

Answer 9

has the value 1

Question 10

identifier false

Answer 10

has the value 0

Question 11

regional operators

Answer 11

allow comparisons
req 2 operands
return 1 if expresion true, 0 otherwise

Question 12

comparing diff data types

Answer 12

unpredictable results produced

Question 13

regional operators

Answer 13

==
!=
<
<=
>
>=

Question 14

logical (boolean) operators

Answer 14

enable you to combine logical expressions

Question 15

logical operators list

Answer 15

! (not)
&& (and)
|| (or)

Question 16

putting !

Answer 16

putting ! in front of a logical expression reverses its value

Question 17

eg of using logical operators

Answer 17

(x > 0 && x <= 50)

cannot write this:
0 < x <= 50)

Question 18

precedence of operators

Answer 18

evaluated left to right

parentheses can override precedence

Question 19

short-circuit evaluation

Answer 19

evaluation of logical expression stops when value of expression known

• if first part of && false, whole lot is false
• if first part of || true, whole lot is true

Question 20

{ } and if statements

Answer 20

only use { } if you need to group together multiple statements within the if statement. Don’t use if there is only 1 statement in a branch

Question 21

IF syntax

Answer 21

• condition must be in ()
• no ; after the condition
• can leave out ELSE if not needed

Question 22

the keyword CONST

Answer 22

useful for values that are used multiple times in the program

Question 23

using CONST

Answer 23

instead of if (temp > 37) ...
use if (temp > NORMAL_TEMP), with NORMAL_TEMP being assigned to be 37 at the start

as it is more readable, otherwise significance of 37 not clear. Also makes it easier to change later on if you wanted to, for example, change it to 38

Question 24

Notes on constants

Answer 24

common practice to name constants with all capitals

eg. PI, NORMAL_TEMP, TAXRATE, PRSI

Question 25

Using const example

Answer 25

const double NORMAL_TEMP = 37;