c language - operators

7/29/2019 C language - operators

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Operators

Kinds of Operators

Precedence of Operators

Type Casting


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Classifications

Arithmetic operators

Relational operators

Logical operators

Assignment operators

Increment and decrement operators

Conditional operators

Bitwise operators

Special operators


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Arithmetic Operators

Operator for arithmetic operation Unary operator : +, -

Binary term operator : +, -, *, /, %

% is purely integer operator.

7/4 = 1 ; 4%7 = 4;9.0 / 2= 4.5; 7%4 = 3;

9/4 = 2 ; 9/2.0 = 4.5;

4/7 = 0; 9.0/2.0 = 4.5;

9.0 % 2;

9%2.0;

9.0%2.0;

a-b a+b a%b

a*b -a*b a/b


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Integer arithmetic

Note: In modulo division, the sign of the resultis always the sign of the first operand

(dividend).

6/3 = 2

-6/3 = -2

6/-3 = -2

-6/-3 = 2

7%3 = 1

-7%3 = -1

7%-3 = 1

-7%-3 = -1


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Precedence of arithmetic operators

Left to right evaluationEx:

1. a = 9, b = 12, c = 3

x = a b/3 + c*2 - 1

High priority * / %

Low priority + -


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Precedence of arithmetic operators

Order of evaluation can be changed byintroducing parentheses

Ex:

1. a = 9, b = 12, c = 3

x = a b/(3 + c)*(2 1)

For nested parentheses, inner most

parentheses will be first evaluated.

Ex:

x = 9 ((12/3) + 3*2) 1


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Relational Operators

Compare two value.

Result : true (1)or false (0).

Zero is false, non zero integer is true.


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Examples:

7>=4 = 1; 7>=7 = 1;

94 = 1

7>9 = 0;

7


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Logical Operators

Operators

&& Logical AND ! Logical NOT

|| Logical OR

An expression which combines two or more relational

expressions is called as logical expression or compoundrelational expression.

a < b && b < c


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Logical Operators

Truth tableOp1 Op2 Op1 && Op2 Op1 || Op2

Non zero Non zero 1 1

Non zero 0 0 1

0 Non zero 0 1

0 0 0 0


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Assignment Operators

Ex:

Expr1 = Expr1 op Expr2 Expr1 op= Expr 2

x = x * y + 1; x *= y + 1;

x = x * (y+1)

sum = sum + i ; sum += i ;


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Increment & Decrement Operators

Operator++, --

Prefix operator (evaluation and then assignment)

Postfix operator (assignment and then evaluation)

Cannot use at expression, only at variable

Cannot apply at real type

n = 1;

x = ++n; // x=2, n=2

n = 1;

x = n++; // x=1, n=2

(a + b)++ // error


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Increment & Decrement Operators

Examples:

1. a[i++] = 10;

2. m = n++ -j+10;

=> a[i] = 10;

i = i+1


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What is the output of the following C

segments: ( Be careful )

x = 0 ;

if ( x++ )

y = 1;

else

y = -1;

printf (x=%d,y=%d\n, x,y);


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What is the output of the following C

segments: ( Be careful )

x = 0 ;

if (++x)

y = 1;

else

y = -1;

printf (x=%d,y=%d\n, x,y);


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The Conditional Operator

Expr1 ? Expr2 : Expr3 (3 Terms Operator)

m = a > b ? (c > a ? c : a) : (c > b ? c : b) ;

max = x > y ? x : y ;

if (x > y)

max = x;

else

max = y;


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Bitwise Operators

Operand should be integer type


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Bitwise Operators

Precedence

Operator Precedence

~

> >>>

&

^

|

(H)

(L)


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Bitwise Operators

Bitwise AND

10012 & 00112 = 00012

To extract the special area in variable by masking thatarea

Bit OR

10012 | 00112 = 10112

Exclusive OR

10012 ^ 00112 = 10102

1s Complement

~ 000010102 = 111101012


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Bitwise Operators

Bitwise Shift Operator

Shift left()

x > y = x / 2y


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Special operators

1. The Comma operator:

used to link the related expressions together.

Evaluated left to right has lowest precedence, parentheses are

necessary.

Ex:value = (x=10,y=5,x+y);


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Special operators

2. The sizeof operator:

It returns the number of bytes the operand

occupies.

the operand can be a variable, constant or a

data type qualifier.

Ex:

m = sizeof(sum);

n = sizeof(long int);

k = sizeof(235L);

Category Operator Associativity


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Category Operator Associativity

Postfix () [] -> . ++ - - Left to right

Unary+ - ! ~ ++ - - (type) * &

sizeofRight to left

Multiplicative * / % Left to rightAdditive + - Left to right

Shift > Left to right

Relational < >= Left to right

Equality == != Left to right

Bitwise AND & Left to right

Bitwise XOR ^ Left to right

Bitwise OR | Left to right

Logical AND && Left to right

Logical OR || Left to right

Conditional ?: Right to left

Assignment= += -= *= /= %= >>=


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Operator Precedence

Example:

3 + 4*5 6/2 + 7*8

3 + 20 - 6/2 + 7*83 + 20 - 3 + 7*8

3 + 20 - 3 + 56

23 -3 +5620 + 56

76


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Operator Precedence

Example:

x = y += z -= 4

x = y += (z -= 4)x = (y += (z -= 4))

(x = y += (z -= 4))


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Operator Precedence

a = x + y - z ; // Left Association

b = -x ; // Right Association

c = -x++ ;

d = -++x ;

e = -x + z ;

e = ++z + z--;

f= p++ + p++;


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Type conversionAutomatic type conversion

Operands of lower type is automatically

converted to higher type and result is of

higher type.

1. Float to int causes truncation of fractional

part.

2. Double to float causes rounding of digits.

3. Long int to int causes dropping of excess

higher order bits.

T i


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Type conversion

Example:

int i,x;

float f;

double d;long int l;

Expression:

x = l / i + i * f - d

long

long

float

float

float

float

int double

double


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Type ConversionCasting a value

The process of local conversion is known as casting a

value.


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Type ConversionCasting a value

Examples:

x = (int)7.5

A = (int)21.3/ (int)4.5

B = (double)sum/n

Y = (int)(a + b)

P = cos ((double)x)


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Managing I/O: Input-Output

Statements, formatted I/O.


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getchar()

Used to read a single character from the

standard input unit (keyboard)

#include

Ex: char name;

name=getchar();

Variable name = getchar();


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Character test functions

char character;

character=getchar();

isalpha(character): it assumes a non-zero

value(TRUE) if the argument character

contains an alphabet, otherwise it assumes

zero.

isdigit(character)


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Function Test

isalnum(c) Is c an alphanumeric character?

isalpha(c) Is c an alphabetic character?

isdigit(c) Is c a digit?islower(c) Is c a lower case letter?

isprint(c) Is c a printable character?

ispunct(c) Is c a punctuation mark ?

isspace(c) Is c a white space character?

isupper(c) Is c an upper case letter?


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char c;c=getchar();

if(isalpha(c)>0)

printf(letter);

else

if(isdigit(c)>0)

printf(digit);

else

printf(not alphanumeric);


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putchar()

Used to write characters one at a time to the

terminal

Ex: answer = Y;

putchar(answer);

putchar(variable name );


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putchar()

Ex:

char alphabet;

alphabet = getchar();

if(islower(alphabet))

putchar(alphabet);


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Formatted Input: Scanf () function

Its an input function, used to read values in

run time.

Its a call by address function.

It is predefined function in stdio.h

If & is missing, variable contains garbage value.

scanf (control string, &var1, &var2,-------);


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Field specifications

The field specification for reading an integer

number is

% wc

%conversion specification

w field width of the number to be read

d data type character in integer modec character mode

s string mode

% wd % ws

I /O Formats


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I /O Formats

% is called format specifier.

%d : Decimal integer

%0 : Octal integer

%0x : Hexadecimal integer

Data type format

Int %d

Float %f

Char %c

Long %ld

Double %lf

Unsigned %u

String %s


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Scanf () function

Example2: int a, b, c;

scanf(%d %d %d, & a, &b, &c);

Example3: int d, m, y;

scanf(%d, %d ,%d, & a, &b, &c);

Example4: int x; float y; char ch;

scanf(%d %f %c, & x, &y, &ch);Order of the variables and order of formats must

match.


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Try this..

1. scanf(%2d %5d, &a,&b);

Input1: 50 31426

Input2: 31426 50

2. scanf(%d %*d %d, &a, &b);Input: 123 456 789

skipped because of*


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gets()

recieves a string from keyboard until the user

presses enter key.

Spaces and tabs are acceptable as part of

input string.

f(% ) ( )


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scanf(%s, a); gets(a);

If user enters sankar dayal

sharma, only sankar is stored in

array a.

a

entire sankar dayal sharma is

stored in array a.

a

scanf() reads characters until

user press space bar.

gets() reads characters until

user presses enter key.

scanf() reads only one word. gets() function can read

multiword strings.

gets(arrayname)

Formatted function Unformatted function

Sankar \0

Sankar dayal sharma \0


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Formatted output: Printf()

It is an output function.

Its a call by value function.

It is predefined function in stdio.h.

Example: int a = 25;

Printf(%d,a);

printf(control string, arg1, arg2,-------);


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printf()

Type the following and observe the results:

int x = 25; float y = 10.68f; char ch = g;

1. printf(%d %f %c,x,y,ch);

2. printf(%d\n %f\n %c,x,y,ch);

3. printf(%d\t %f \t%c,x,y,ch);

4. printf(%d, %f, %c,x,y,ch);\n and \t cannot be used in scanf() but can be

used in printf.

printf(result is %d\n,x*2+y);


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scanf() printf()

Input function Output function

To read values at run time To display values

Call by address function. Call by value function.

deals with keyboard deals with monitor

We cant write \n and \t Not allowed

It can contain onlyvariables.

It can contain variables,messages and expressions.


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puts()

It outputs a string to the screen.

puts(GRIET);


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puts()

Type the following and observe the results:

1. Printf(hyd\n);

Printf(sec\n);

Printf(cyb\n);

2. Puts(hyd);

Puts(sec);Puts(cyb);

3 printf(%d );


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3. printf( %d , . );

printf(%d,A);

printf(%d,7);printf(%d,\0);

4. printf(%c,\0);

5. float a = 123.6789;

printf(%.2f,a);

printf(%.3f,a);

printf(%f,a);


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6. int a=4567;

printf(%7d,a);

printf(%.07d,a);

printf(%2d,a);

printf(%d,a);

Try this..Display 07:08:09


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7. printf(\\n);

printf(\\);

printf(\);

printf(%%);

printf();

printf(%);printf(\%);

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