Basic c operators

Chapter 4: Basic C Operators
In this chapter, you will learn about:
Arithmetic operators
Unary operators
Binary operators
Assignment operators
Equalities and relational operators
Logical operators
Conditional operator

Principles of Programming - NI July2005 1

Arithmetic Operators I
In C, we have the following operators (note
that all these example are using 9 as the
value of its first operand)


Arithmetic Operators II
There are 2 types of arithmetic operators
in C:
unary operators
operators that require only one operand.
binary operators.
operators that require two operands.


Unary Operator
C Operation Operator Example
Positive + a = +3
Negative - b = -a
Increment ++ i++
Decrement -- i--

The first assigns positive 3 to a
The second assigns the negative value of a to b.
i++ is equivalent to i = i + 1
i-- is equivalent to i = i-1


PRE- / POST-Increment
It is also possible to use ++i and --i instead of
i++ and i--
However, the two forms have a slightly yet
important difference.
Consider this example:
int a = 9;
printf(“%dn”, a++);
printf(“%d”, a);
The output would be:
9
10

PRE- / POST-Increment cont…
But if we have:
int a = 9;
printf(“%dn”, ++a);
printf(“%d”, a);
The output would be:
10
10
a++ would return the current value of a and
then increment the value of a
++a on the other hand increment the value of
a before returning the value


The following table illustrates the difference between the prefix and postfix
modes of the increment and decrement operator.

int R = 10, count=10;

++ Or -- Equivalent R value Count
Statement Statements value
R = count++; R = count;
10 11
count = count + 1
R = ++count; count = count + 1;
11 11
R = count;
R = count --; R = count;
10 9
count = count – 1;
R = --count; Count = count – 1;
9 9
R = count;


Binary Operators
C Operation Operator Example:
Addition + a+3
Subtraction - a-6
Multiplication * a*b
Division / a/c
Modulus % a%x

The division of variables of type int will always
produce a variable of type int as the result.
You could only use modulus (%) operation
on int variables.


Assignment Operators
Assignment operators are used to combine the
'=' operator with one of the binary arithmetic
operators
In the following slide, All operations starting from
c=9
Operator Example Equivalent Results
Statement
+= c += 7 c=c+7 c = 16
-= c -= 8 c=c–8 c=1
*= c *= 10 c = c * 10 c = 90
/= c /= 5 c=c/5 c=1
%= c %= 5 c=c%5 c=4

Precedence Rules
Precedence rules come into play when there is a mixed
of arithmetic operators in one statement. For example:
x = 3 * a - ++b%3;
The rules specify which of the operators will be
evaluated first.

Precedence Operator Associativity
Level
1 (highest) () left to right
2 unary right to left
3 * / % left to right
4 + - left to right
5 (lowest) = += -= *= /= %= right to left


Precedence Rules cont…
For example: x = 3 * a - ++b % 3;
how would this statement be evaluated?

If we intend to have the statement evaluated
differently from the way specified by the
precedence rules, we need to specify it using
parentheses ( )
Using parenthesis, we will have
x = 3 * ((a - ++b)%3);
The expression inside a parentheses will be
evaluated first.
The inner parentheses will be evaluated
earlier compared to the outer parentheses.


Equality and Relational Operators
Equality Operators:
Operator Example Meaning
== x == y x is equal to y
!= x != y x is not equal to y

Relational Operators:
Operator Example Meaning
> x>y x is greater than y
< x<y x is less than y
>= x >= y x is greater than or equal to y
<= x <= y x is less than or equal to y


Logical Operators
Logical operators are useful when we want to
test multiple conditions.
There are 3 types of logical operators and they
work the same way as the boolean AND, OR and
NOT operators.
&& - Logical AND
All the conditions must be true for the whole
expression to be true.
Example: if (a == 10 && b == 9 && d == 1)
means the if statement is only true when a ==
10 and b == 9 and d == 1.


Logical Operators cont…
|| - Logical OR
The truth of one condition is enough to make
the whole expression true.
Example: if (a == 10 || b == 9 || d == 1)
means the if statement is true when either
one of a, b or d has the right value.
! - Logical NOT (also called logical negation)
Reverse the meaning of a condition
Example: if (!(points > 90))
means if points not bigger than 90.


Conditional Operator
The conditional operator (?:) is used to
simplify an if/else statement.
Syntax:
Condition ? Expression1 : Expression2
The statement above is equivalent to:
if (Condition)
Expression1
else
Expression2


Conditional Operator cont…
Example 1:
if/else statement:
if (total > 60)
grade = ‘P’
else
grade = ‘F’;
conditional statement:
total > 60 ? grade = ‘P’: grade = ‘F’;
OR
grade = total > 60 ? ‘P’: ‘F’;

Conditional Operator cont…
Example 2:
if/else statement:
if (total > 60)
printf(“Passed!!n”);
else
printf(“Failed!!n”);

Conditional Statement:
printf(“%s!!n”, total > 60? “Passed”: “Failed”);


SUMMARY
This chapter exposed you the operators used
in C
Arithmetic operators
Assignment operators
Equalities and relational operators
Logical operators
Conditional operator
Precedence levels come into play when there
is a mixed of arithmetic operators in one
statement.
Pre/post fix - effects the result of statement


Basic c operators

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Basic c operators