Operators & Exressions

Operators

Introduction

An operator specifies an operation to be performed. C is rich in operator. Operators join the various variables and constants to from an expression.

Some operator requires one operand and some require more than one operands.

An operator is a symbol that tells the computer to perform certain mathematical or logical manipulation in data stored in variables.

C is extremely rich in operators It has as many as 45 different operators.

Operators Arithmetic operators Arithmetic Operators are used to Arithmetical calculation. There are five Arithmetic operators in C: Operator Purpose + Addition - Subtraction * Multiplication / Division % Remainder after integer division Operators Relational operators Relational operators are used to compare two operands and to check whether they are equal, unequal, greater than and lesser than other. There are 6 relational operators: Operator Meaning < Less than > Greater than <= Less than equal to >= Greater than equal to == Equal to != Not equal to The value of the relational operator is either one or zero. If the relation is true, result is 1 otherwise it is 0. Operators Logical operators Logical operators are used to combine two or more relational expressions. There are three logical operators: Operator Meaning && Logical And || Logical or ! Logical not The expression which combines two or more relational expressions is termed as logical expression or compound relational expression. The result of a logical expression is either one or zero. Example: a) if (age > 50 && weight < 80) b) if (a < 0 || ch = = 'a') c) if ( ! (a < 0)) Operators Increment & Decrement operators These types of operators operate on only one operand, therefore these operators are also called Unary operators. These two powerful operators in C are + + (Increment), _ _ (Decrement). Operands must be declared as variables not a constant. These operators may be used either after or before the operand. When they are used before the operand, it is termed as Prefix while when they are used after the operand they are termed as Postfix. In prefix operations the value of operator is incremented or decremented first and then the expression is evaluated. Prefix operators has the effect of Change then use. In postfix operation the expression is evaluated first and then the value of operator is either incremented or decremented. Postfix operators has the effect of Use Then Change. e.g.: b=a++; this is postfix increment expression. In the expression firstly b=1; thena=a+1; will be executed , while in prefix increment expression b=--a; firstly a =a-1;then b=a; will be executed. An example program clarifies the Postfix and Prefix operators: Output of the program: Operators Bitwise operators The smallest element in memory on which we are able to operate as yield is a byte; and we operate on it by use of the data type char Bitwise operator is used for manipulation of data at bit level. These operators are used for testing the bits, shifting them right to left. Bitwise operatormay not be applied to float or double data type. This is a powerful feature of C to manipulate a bit. The programmer can access and manipulate individual bits within a piece of data. Some of the bitwise operators in C are: Operator Meaning & Bitwise Logical AND | Bitwise Logical OR ^ Bitwise Logical XOR << Left Shift >> Right Shift ~ Once Compliment Operators Conditional & ternary operators The conditional operator? and: are sometimes called ternary operators. A ternary operator is one which contains three operands. The general form of ternary operator is: exp 1 ? exp 2 : exp 3 The operator works as, if exp 1 is evaluated first. If the result is true then exp 2 is executed, otherwise exp 3 is executed. A program of ternary operator: Output of the program: Operators The comma operators This operator is used to link the related expression together the expression is separated by the, operator. An example program showing uses of comma operator: Output of the program: Here firstly value 1 is assigned to a, followed by this 2 is assigned to b, and then the result of a+b is assigned to c. The comma operator is often used in conjunction with a control statement called For. Operators Size of operator The size of operator returns a number of bytes the operand occupies in memory. The operand may be a variable, a constant or a data type qualifier. It is a compile time operator. An example of size of operator: Output of size of operator: The output of the above program is 2 because int occupies two byte in memory. The size of operator is generally used to determine the length of entities called arrays and structures when their size is not known to the programmer. Operators Assignment operator Assignment operators are used to assign the result of an expression to a variable. The most commonly used assignment operator is (=). eg:      i=i+10;       i=i+10 is an assignment expression which assigns the value of i+10 to i. Expression like   i=i+10,  i=i-5,  i=i*2 etc. can be rewritten using shorthand assignment operators. e.g.:   i=i+5 is equivalent to i+=5             i=i*(y+1)  is equivalent to   i*=(y+1) Operator Precedence: While executing an arithmetic statement which has two or more operators, we may have some problems about how exactly does it get executed. To answer these questions satisfactorily we have to understand the precedence of operators. Precedence defines the sequence in which operators are to be applied on the operands. Operators of same precedence are evaluated from left to right or right to left, depending upon the level. This is known as associativity property of an operator. Summary of precedence of associativity is given below: Description Operator Associativity Function Expression ( ) Left to Right Array Expression [ ] Left to Right Structure Operator -> Left to Right Structure Operator . Left to Right Description Operator Associativity Unary minus - Right to Left Increment/Decrement ++/-- Right to Left One's Compliment ~ Right to Left Negation ! Right to Left Address of & Right to Left Value at address * Right to Left Type cast (type) Right to Left Size in bytes sizeof Right to Left Description Operator Associativity Multiplication * Left to Right Division / Left to Right Modulus % Left to Right Addition + Left to Right Subtraction - Left to Right Description Operator Associativity Left Shift << Left to Right Right Shift >> Left to Right Description Operator Associativity Less Than < Left to Right Less Than Equal to <= Left to Right Greater than > Left to Right Greater than Equal to >= Left to Right Description Operator Associavity Equal to == Left to Right Not equal to != Left to Right Description Operator Associavity Bitwise AND & Left to Right Bitwise XOR ^ Left to Right Description Operator Associavity Bitwise OR ^ Left to Right Description Operator Associavity Logical AND && Left to Right Logical OR || Left to Right Description Operator Associavity Conditional ?: Right to Left Description Operator Associavity Assignment = Right to Left Assignment *=   /=   %= Right to Left Assignment +=   -=   &= Right to Left Assignment ^=   |= Right to Left Assignment <<=   >>= Right to Left Description Operator Associavity Comma , Right to Left Operators Type modifier The basic data types may have modifier preceding them to indicate special properties of the object being declared. These modifiers change the meaning of the basic data types to suit the specific needs. These modifiers are unsigned, signed, long and short. It is also possible to give these modifiers in combination, e.g., unsigned long int. eg:- Modifier for char Data Type main() { char ch=291; printf("%d\t%c\n",ch,ch); } output:- 35 Here ch has been defined as a char ,and char cannot take a value bigger than +128.That is why assigned value of ch is 291 and is considered to be 35 (291-128-128). Data type Range Bytes occupied Format signed char -128 to +127 1 %c unsigned char 0 to 255 1 %c short signed int -32768 to 32767 2 %d short unsigned int 0 to 65535 2 %u long signed int -2147483648 to +2147483647 4 %ld long unsigned int 0 to 4294967295 4 %lu float -3.4e38 to 3.4e38 4 %f double -1.7e4932 to +1.7e308 8 %lf long double -1.7e4932 to 1.7e4932 10 %lf Expressions   Evaluation of expression   An expression is a combination of variables, constants and operators arranged according to the syntax of the language.   C can handle any complex expression with ease.   It is little bit different from algebraic expression.   Algebraic Expressions C Expressions axb-cxd a*b-c*d (m+n)(a+b) (m+n)*(a+b)   Evaluation of expression:   We can evaluate an expression by using assignment statement. As   Variable = Expression.   e.g. :   Temp = ((f * cos(x)/sin (y))+(g * sin(x)/cos(y)))   All relevant variables must be assigned values before the evaluation of the expression.   Type conversion in expression:   To effectively develop C programs, it would be necessary for you to understand the rules that are used for the implicit conversion of operands.   If an expression contains an operation between an int and a float, the int would be automatically promoted to a float before carrying out of operation.         Expressions   Automatic type conversion   If the operands are of different types the lower type is automatically converted to thehigher type before the operation proceeds The result is of the higher type   Given below is the sequence of rules that are applied by evaluating expressions.   Operator 1 Operator 2 Result Long Double any Long Double Double any Double Float any Float Unsigned Long Int any Unsigned Long In Long Int any Long Int Unsigned Int any Unsigned Int   Final result of an expression to the type of the variable on the left of the assignment signed before assigning the value to it.   However, the following changes are introduced during the final assignment:   1. Float to Int causes truncation of the fractional part.   2. Double to float causes rounding of digits.   3. Long int to int causes dropping of the excess higher order bits   Type Casting:   Casting a value is a forcing a type conversion in a way that is different from the automatic conversion and this process is called type cast. This should be clear from the following examples:   An example of automatic conversion:     Output of automatic conversion:     The answer turns out to be 1.000000 and not 1.5 this is because, 6 and 4 are both integers, and hence 6/4 yields an integer, 1.   This 1 when stored in a is converted to 1.000000. But what if you don't want the question to be truncated. One solution is to make either x or y as a float.   The general form of casting is:   (type_desired) expression; where type_desired : standard C data types and expression: constant, variables or an expression.   An example of type casting:     Output of type casting example:     Type Definition using typedef   C allows us to create data types via the typedef statement.   The format of typedef statement is:   typedef data type new_type_name;   Example:   typedef int units; units bat1,bat2; /*this statement is equivalent to int bat1,bat2*/