4 Operators and Expressions

8/14/2019 4 Operators and Expressions

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4 Operators and Expressions

4.1

4.2

Operators

Arithmetic Operators4.2.1Unary Operator4.2.2Binary Operators4.2.3Increment and Decrement

Operator4.2.4Precedence of arithmetic

Operators

Relational Operators

Logical Operators

Assignment Operator

Precedence of Operators

Expressions

4.7.1Mixed Mode Expressions andCast

4.7.2Spacing and Parentheses

Sample Programs4.8.1Sample Program 14.8.2Sample Program 24.8.3Sample Program 3

Summary

Exercises

Learning Objectives

Upon successful completion of this chapter, students will be

able to:

Describe operatorsDemonstrate an understanding of arithmetic operators,

relational operators, and logical operatorUse assignment operatorDemonstrate an understanding of operator precedence

Describe the various forms of expression

4.3

4.4

4.5

4.6

4.7

4.8

4.9

4.10


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Fundamentals to Programming

In this chapter, we will discuss the operators and expressions, and the assignment statementin C++ programming language.

4.1 Operators

A mathematician uses more than just the variables. A mathematician can add them together,

subtract them, multiply them, and perform an almost endless list of other operations.

C++ offers the same set of basic operations. C++ programs can multiply, add, divide, and so

forth. Programs have to be able to perform these operations in order to get anything done.

4C++ is very rich in built-in operators. Operator triggers some computations when applied tooperands in an expression. The commonly used operators are as follows:

Arithmetic operators

Relational operatorsLogical operator

Assignment operator

Table 4-1 shows the commonly use operators in C++ programming language.

Arithmeticoperators

+-*

/%

Table 4-1

Relationaloperators

>=


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Operators and Expressions

Arithmetic Operator+-+-

*/

%

Table 4-2

DescriptionUnary plus

Unary minus

Addition

SubstractionMultiplication

Floating-point division (floating-point result)

Intreger division (no fraction part)Modulus (remainder from the integer division)

Arithmetics operators

The first two operators are unary operator. Unary oprarators just take one operand(argument). The remaining five are binary operators. Binary operators take two operands.

4.2.1 Unary Operator

The + and - operator can be unary or binary. A unary operator has only one operand (inother words, unary operators take a single argument) while a binary operator has twooperands. For example, the - operator in -5 can be considered as a unary operator to negatenumber 5, whereas the - operator in 4 -5 is a binary operator for subtracting 5 from 4.

You an assign a positive or negative number to a variable by using a unary + or-. For

instance,

m = +12

n = -12

// Assigns 'm' a positive 12

// Assigns 'n' a negative 12

4

Unary operators operate on a single value. Thus sizeof operator, decrement operator and

increment operator are unary operators.

Here is a program example using unary operator.

// Program that uses unary operator#include

main(){

intintintint

abcd

====

+10;-a;-b;-(-b);

====

"


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Here is the output.

abcd

====

10-a = -10-b = 10-(-b) = -10

4.2.2 Binary Operators

A binary operator is one that has two arguments. If you can say var1 op var2, op must

be a binary operator. The most common binary operators are the simple operations youperformed in grade school.

4 There are five standard arithmetic operators in C++ as shown in following table. Thearithmetic operators are use to manipulate values in programs.Operator Description+Addition

-Subtraction

*Multiplication

/Division

%Modulus

(remainder)

Table 4-3

Example25 + 2, the result is 27

25 - 2, the result is 23

25 * 2, the result is 50

25 / 2, the result is 11 for integer; 11.5 for floating point

25 % 2, the result is 1 (that is, 25 / 2 = 11 with

remainder of 1)

Binary arithmetic operators

When you divide two integers, the result will be an integer. In other words, any fractional

part of the result is lost. For example, the result of25 / 2 is 11, even though is 11.5 in amathematical expression.

When you use modulus operator with two integers, the result is an integer with the value ofthe remainder after division takes place, so the result of25 % 2 is 1.

Here are some examples of operations involving integer variables. The expressions on the left

evaluate to the values on the right. Let say

m=5n=2

Expressionm+nm-nm*nm/nm%n

Table 4-4

Result 7

3

10

2

1 Remainder is discarded

Produces remainder of division

Arithmetic operation involving integer variable

When the forward slash / is applied to integer operands, any remainder with be truncated

while the modulus (%) produces the remainder of the division.

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The modulus operator (%), increment operator (++) and decrement operator (--) only can beused with integers. You can not use with floating-point data.

Here is an example using arithmetic operators.

// Program using arithmetic operators# include

main(){

int value1 = 43, value2 = 10, sum;int difference, product, quotient, modulus;

sum = value1 + value2;difference = value1 - value2;product = value1 * value2;quotient = value1 / value2;modulus = value1 % value2;

cout


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Operator Called++Pre-increment

Expression++m

++ Post-increment m++

-- Pre-decrement --n

4 -- Post-decrement n--

Explanationm = 5, n = 2 6Increment m by 1, then thenew value of m in the

expression in which m

resides.

Use the current value of m in6

the expression in which mresides, then increment m by

1.

1Decrement n by 1, then usethe new value of n in the

expression in which n

resides.

Use the current value of n in1the expression in which n

resides, then decrement n by

1.

Table 4-5 The increment and decrement operators

For pre-increment and pre-decrement, (i.e., ++a or --a), the operation is performed and the

value is produced. For post-increment and post-decrement (i.e. a++ or a--), the value is

produced, then the operation is performed.

Here is an example using pre-increment and post-increment operator.

// Program to show pre-incrementing and post-incrementing operation

#include

main(){

int n;n = 5;cout


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Here is the output.

566

556

4.2.4 Precedence of arithmetic Operators

Arithmetic operators have the following precedence:

Highest Arithmetic Operator Operator

+ - ++ --UnaryOperators

Arithmetic multiply, divide, remainder (modulus) * / %

+-Arithmetic add

and subtract

4

LowestFigure 4-1 Precedence of arithmetic operators

When you combine mathematical operations in a single statement, you must understandoperator precedence, or the order in which parts of a mathematical expression are evaluated.

Multiplication, division and modulus always take place prior to addition and subtraction in an

expression. For the expression

int result = 2 + 3 * 4;

The results is 14, because the multiplication (3 * 4) occurs before adding 2. You can

override normal operator precedence by putting the operation to perform in parentheses. Theexpression

int result = (2 + 3) * 4;

results in 20, because the addition within the parentheses takes place first, and then that result(5) is multiplied by 4.

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4.3 Relational Operators

Relational operators are also known as comparison operators. A relational operator compares

two items. There are six relational operators in C++ as shown in the table below.

Operator===!=

Table 4-6

4

DescriptionLess Than

Greater ThanEqual to

Less than or equal to

Greater than on equal to

Not equal to

Relational operators

True Example347575

2== 7= 3!= 6

False Example823813

4== 9=2!= 3

The results of evaluation of a relational operation is either true (represented by 1) or false

(represented by 0).

When you use any of the operators that have two symbols (==, =, or !=), you cannotplace any whitespace (blank space) between the two symbols.

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Here is a sample program testing therelational operators.

// Program that testing the relational operators#include

main()

{cout


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Here is the output.

The results of evaluation of a relational operationtrue (represented by 1) or false (represented by 0).

Testing greater than

100 > 10 results in 110 > 100 results in 0100 > 100 results in 0

Testing less than10 < 100 results in 1100 < 10 results in 0100 < 100 results in 0

4Testing greater thanor equal to100 >= 10 results in 110 >= 100 results in 0100 >= 100 results in 1

Testing less than or equal to10


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Here is a sample program testing the logical operators.

// Program that testing the logical operators#include

main(){

// Output to screencout


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4.5 Assignment Operator

C++ has several assignment operators. The most commonly used assignment operator is =.

The assignment operator is used to change the value of a variable. Assignment operations

using = has the general form

identifier = expression;

where identifier generally represents a variable and expression represent a value, constant, a

variable or a more complex expression. Here are some examples of assignment operations.

4num_of_seat = 50;interest_rate = 0.05;char newline = '\n';area_of_rectangle = (width + height) * 2;salary = basic_pay + overtime_hours * overtime_rate;

There is a shorthand notation that combines the assignment operator (=) and an arithmeticoperator so that a given variable can have its value changed by adding, subtracting,

multiplying by, or dividing by a specified values. The general form is

identifier = arithmetic_operator (expression);

The expression can be another variable, a constant or more complicated arithmetic expression.

Below are examples:

Assignment Statementcount += 2;total -= discount;bonus *= 2;time /= rush_factor;change %= 100;amount *= count1 + count2;

Equivalent tocount = count + 2;total = total - discountbonus = bonus * 2;time = time / rush_factorchange = change % 100;amount = amount * (count1 + count 2)

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// Program that demonstrating the assignment operators#include

main(){

// Variable declaration and initializationfloat m = 0.0, n = 0.0, result = 0.0;

// Prompt for inputcoutm>>n;

// Testing the assignment (=) operatorresult = m + n;cout


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4.6 Precedence of Operators

The hierarchy of operator precedence from highest to lowest is summarized in figure below.

Highest Operator CategoryUnary OperatorsArithmetic multiply, divide, remainder

Arithmetic add and subtract

Relational operatorsLogical operators

Assignment

Precedence of operators

Operator++ -- + -*/%+-> < >= ++m * --n + 4&& p++ + q-- * 4 < x++ * y-- + 4;

cout


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4.7 Expressions

Expressions in C++ are formed by properly combining operators, variables and constants. As

in algebra, C++ expression can be complex. Parentheses are used to force the order of

evaluation. An expression may also contain spaces for readability. Here are some examplesof C++ expressions.

gross_pay deductions(basic_pay + hours * rate) (socso +epf)(k * k - 5 * j* h) >100(gender == 'm') && (age > 20)(size == 'M' || size = 'L') && price


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// Program to illustrate data conversion#include

main(){

int a = 5;float b = 2, c = 3.0, d;d = c + a / b;cout


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Here is the output.

Result = 15

4

95


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4.8 Sample Programs

4.8.1 Sample Program 1

Program 4-11 begins with a comment that explains what the program does. The body of the

main function includes a declaration section where the variables w, h, perimeter and

area are defined and initialized. It is follow by a sequence of executable statements. These

statements compute the perimeter and area. Finaly, it display results to screen.

// Program to compute perimeter and area#include

main()

{// Variable declaration and initializationfloat w = 0.0, h = 0.0, perimeter = 0.0, area = 0.0;

// Prompts for inputcoutw;couth;

// Computes the perimeterperimeter = 2 * (w + h);

// Computes the areaarea = w * h;

// Output results to screencout


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Program 3-11 begins with a comment that explains what the program does. The body of themain function includes a declaration section where the variables value1 and value2, and

are defined. It is follow by a sequence of executable statements. These statement display thecomparison results of variables value1 and value2.

// Program that comparing two numbers entered from keyboard#include

main(){

// Variable declaration and initializationfloat value1 = 0.0, value2 = 0.0;

// Input and output statements

coutvalue1;coutvalue2;

// Output result to screencout


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Program 4-13 computes the amount earned. The program starts with the declaration andinitialization of constant variable rate, and variable total and day. Given the number of

days worked and the daily rate, the program first converts or casts the value ofday (aninteger) to a floating-point number before using it in the multiplication. Finaly, it displays the

result to screen.

// Program to calculate the amount of money earned#include

main(){

// Constant & variable declaration and initializationconst float rate = 50.00;float total = 0.00;int day = 0;

// Prompts for inputcoutday;

// Computes the perimetertotal = (float) day * rate; // Converts day to floating point

// Output results to screencout


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4.9 Summary

The commonly used operators in C++ are arithmetic operators, relational operators,

logical operators, and assignment operators.

There are five standard arithmetic operators: +, -, *, /, %.

There are six comparison operators: >, =,


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4.10 Exercises

1. What is the numerical value of each of the following expressions as evaluated by the

C++ programming language?

a.

b.

c.

d.e.

f.

g.h.

i.

j.

a.

b.c.

d.

e.f.

g.

h.

i.j.

3+6*4

6/3*8

18 / 2 + 14 /2

16 % 217 % 2

28 % 5

28 % 5 * 3 + 120 / (4 +1)

(10 + 20) / 5

'B' - 'A'

27

1616

0

13

10

4

61

4

2. What is the value of each of the following expressions?

a.b.

c.

d.

e.f.

g.

h.

i.j.

a.b.

c.

d.e.

f.

g.

h.

i.

100

4>16= 42

6 == 9

2 + 5 == 78 + 3


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j. 0

3. Given integer variables x, y, and z with values 10, 7, and 2 respectively. Determinethe valued of each of the following arithmetic expressions.

a.b.c.

d.

e.f.

a.b.

c.

d.

e.f.

x + y - 2zx / z (x * x +y)(x * y) % z

5 * (x + y + z) x / z

x*yx*zy * (x + z) * (x y)

13535

0

90

50252

4

4. Using the values given in exercise 3, determine the values for the each af thefollowing expressions:

a.

b.c.

d.

e.

f.

a.b.

c.

d.e.

f.

x++

x < 2 && z > 5.0y >= x

z != 10

x < y || y > z

(z * 5) == x

110

0

11

1

5. The assignment operator in the C++ programming language is ____________.

a.

b.

c.d.

=

==

=>+=

6. The equal to comparison operator is ____________.

a.b.

c.

d.

===

!=

!!

101


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7. If you attempt to add a float, an int and a long, the result will be a(n) ____________.

a.b.

c.

d.

floatint

long

error message

8. Which assignment is correct?

a.

b.c.

d.

char code = 3;

char code = "three";char code = "3";

char code = '3';

49. What is the output of the following program lines?

a = 'b';b = 'c';c = a;cout

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4 Operators and Expressions