Type casting
Sometimes we need to force the compiler to explicitly convert the value from one type to another where the compiler will not do it automatically.
float result;
result = (float) 21/5;
Here the variable result is a float type and in the expression the division is in forcing to return a float value while both operands are of type integer. In this example the cast operation explicitly converts 21 to a float and causes the division to be carried out as a floating-point division.
char ch = 'A';
int x, y = 5, z = 9;
float f;
x = (int)ch;
f = (float) y * z;
Comparison Between Implicit Typecasting and Explicit Typecasting
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Implicit typecasting
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Explicit typecasting
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(1) It is done by compiler automatically.
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(a) It is done by programmer.
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(2) Needs less coding,
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(b) Need extra coding.
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(3) In general, implicit tasking is employed automatically.
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(c) In general, implicit tasking is employed By programmer for specific purpose.
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(4) The programming environments attributes, initial values are assigned by the system.
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(d) The programming environments attributes, initial values are assigned and set by the programmer.
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(5) No skills are required, in this case for the programmer
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(e) High skills and complete understanding of the program and operating system are the needs of the programmer
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Rules for Evaluation of Expression
1. First, parenthesized sub expression from left to right is evaluated.
2. If parenthesis is nested, the evaluation begins with the innermost sub-expression.
3. The precedence rule is applied in determining the order of application of operators in evaluating sub expression.
4. The associativity rule is applied when two or more operators of the same precedence level appear in a sub expression.
5. Arithmetic expressions are evaluated from left to right using the rules of precedence.
6. When parenthesis is used, the expressions within parenthesis assume highest priority.
Operator Precedence and Associativity
Each operator in C has a precedence associated with it. This precedence is used to determine how an expression involving more than one operator is evaluated. There are distinct levels of precedence and an operator may belong to one of these levels. The operators at the higher level of precedence are evaluated first. The operators of the same precedence are evaluated either from left to right and from right to left depending on the level. This is known as the associativity property of an operator.
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Operators
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Description
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Associativity
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Priority
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()
[]
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Function Call
Array element reference
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Left to right
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1
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+
-
++
--
!
~
*
&
sizeof
(type)
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Unary plus
Unary minus
Increment
Decrement
Logical negation
Ones Complement
Pointer reference (indirection)
Address
Size of an object
Type cast (Conversion)
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Right to Left
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2
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*
/
%
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Multiplication
Division
Modulus
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Left to right
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3
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+
-
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Addition
Subtraction
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Left to right
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4
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<<
>>
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Left Shift
Right Shift
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Left to right
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5
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<
<=
>
>=
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Less than
Less than or equal to
Greater than
Greater than or equal to
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Left to right
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6
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==
!=
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Equality
Inequality
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Left to right
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7
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&
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Bitwise AND
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Left to right
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8
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^
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Bitwise XOR
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Left to right
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9
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Bitwise OR
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Left to right
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10
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&&
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Logical AND
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Left to right
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11
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||
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Logical OR
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Left to right
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12
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?:
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Conditional expression
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Right to left
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13
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=
*=, /=, %=
+=, -=, &=
^=, |=
<<=, >>=
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Assignment operators
Short hand operators
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Right to left
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14
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,
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Comma operator
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Left to Right
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15
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