C Operators, Expressions and Statements                                     Chapter 5

Objectives of this chapter:

• C Operators 
• Arithmetic Operators
• Assignment Operators 
• Logical Operators 
• Relational Operators 
• Bitwise Operators 
• Increement / Decrement Operators 
• Conditional Operators 
• Sizeof Operator 
• Operator Precedence and Associativity 
• Type Conversion and Mixed Expression. 

Operators

• C is rich with numerous operators that can be used in expressions and statements. 
• C uses operators to represent arithmetic operations. 
• The following C Operators are listed in order of decreasing precedence. 

Arithmetic Operators :

• examples: 

Assignment Operators:

• examples: 

Logical Operators:

• an int value is used to representr Boolean values in C language. long and unsigned. 
• a nonzero value is treated as true in C language. 
• a zero value is treated as false in C language. 
• examples 

Relational Operators:

< <= > >= == !=

• examples: 

Bitwise operators:

Bitwise compelement : ~

• This unary operator changes each bit that is a 1 to a 0 and 0 to 1. 

Bitwise AND : &

• This binary operator produces a new value by making a bit by bit comparison between the two operands. For each bit posigion the resulting bit is a 1 only if both corresponding bits in the operands are 1. 

Bitwise OR: |

• This binary operator produces a new valuie by making a bit-by-bit comparison between the two operands. For each bit position, the resulting but is a 1 if either of the corresponding bits in the operands is a bit 1. 

Bitwise Exclusive OR: ^

• this binary operator produces a new value by making a bit-by-bit comparison between the two operands. For each bit position, the resulting bit is a 1 if one or the other (but not both) of the corresponding bits in the operands is a bit 1. 

#include <stdio.h>

main()
{
        int a,b,c;
        a = 0xABCD;
        b = 0xFF00;

        c = ~a;
        printf("~a = %#X\n",c);
        c = a & b;
        printf("~a = %#X\n",c);
        c = a | b;
        printf("~a = %#X\n",c);
        c = a ^ b;
        printf("~a = %#X\n",c);
}

Output:

~a = 0x5432
a & b = 0xABCD
a | b = OxFFCD
a ^ b = Ox54CD

Increment and Decrement operators

• the increment operator (++) increments or increases the value of its operand by one. 
• the decrement operator (--) decrements or decreases the value of its operand by one. 
• there are twi varieties of the ++ and -- operator: 

• the variable's contents is incremented or decremented before using its value in an expression. 

• in the example above, y is increment by 1 first, then multiply y by 2 and assign the result to x. 

• the variable's contents is incremented or decremented before using its value in an expression. 

• in the example above, y is increment by 1 first, then multiply y by 2 and assign the result to x after the affected variable. 

• the variable's contents is used first and is incremented or decremented after the expression has been evaluated. 

• in the example above, y multiplied by two first, and the result is assigned to x, then y is decremented 1. 

• if the increment or decrement operator is used by itself in a statement, for example: 

• there is no difference if the prefix or postfix form is used, both will have the final effect of incrementing or decrementing the variable by one. 

Conditional expression operator:

• the shorthand way to express the if-else statement. 

Type cast operator

• this operator converts its operands value to the type specified by the enclosed keyword. 

sizeof operator

Operator precedence and associativity

• operator precedence refers to which operator is evaluated first in an expression. operators grouped together have the same level of precedence. For example, the relational operators have the same level of precedence but have a higher precedence over the assignment operators. 

• since the * operator has a higher precendence over the - operator, c * d evaluated first, then this result is subtracted from b. 

• operator associativity refers to which operator is evaluated first in an expression that have two or more operators of the same level of precedence. 

• C languange allows for mixed data types in an expression. 

• These different data types in the expression are then converted to be of the same type. 
• C uses a set of rules to convert these different types automatically. 

1. if char and short int (signed or unsigned) are used in an expression, it is automatically converted to int. 
2. a promotion of a data type occurs when a type is converted to a larger type. 
3. in any operation involvinig two different types, both values are converted to the "higher" ranking of the two types. 
4. The ranking of types are as follows (from highest to lowest): 

• long double 
• double 
• float 
• unsigned long int 
• long int 
• unsigned long int 
• long int 
• unsigned int 
• int 

• in an assignment statement, the final result of the calculation is converted to the type of the varialbe that is being assigned a value. 
• this process can result in a promotion or a demotion, in which the value is converted to a lower ranking type.