Introduction

• Variables and constants linked with operators
1. Arithmetic expressions
• Uses arithmetic operators
• Can evaluate to any value
2. Logical expressions
• Uses relational and logical operators
• Evaluates to 1 or 0 (true or false) only
3. Assignment expression
• Uses assignment operators
• Evaluates to value depending on assignment

Arithmatic Operators

  Example:9/5 will be 1, not 1.8
  int a=9, b=5;
  printf("%d", a/b);
  will print 1 and not 1.8

Assignment Operators

• Uses the assignment operator (=)
• General syntax:
variable_name = expression
• Left of = is called l-value,must be a modifiable variable
• Right of = is called r-value ,can be any expression
• Examples:

velocity = 20
b = 15; temp = 12.5
A = A + 10
v = u + f * t
s = u * t + 0.5 * f * t * t

• An assignment expression evaluates to a value same as any other expression
• Value of an assignment expression is the value assigned to the l-value
• Example: value of

a = 3 is 3
b = 2*4 -6 is 2
n = 2*u + 3*v - w is whatever the arithmetic expression 2*u + 3*v - w evaluates to given the current values stored in variables u, v, w

• Several variables can be assigned the same value using multiple assignment operators

a = b = c = 5;
flag1 = flag2 = 'y';
speed = flow = 0.0;

• Easy to understand if you remember that
• the assignment expression has a value
• Multiple assignment operators are right-to-left associative

More Assignment Operators

• +=, -=, *=, /=, %=
• Operators for special type of assignments
• a += b is the same as a = a + b
• Same for -=, *=, /=, and %=
• Exact same rules apply for multiple assignment operators

Logical Operators

Logical Expressions

((count <= 100) || (count>= 200))
((math+phys+chem)/3 >= 60)
((sex == 'M') && (age >= 21))
((marks >== 80) && (marks < 90))
((balance > 5000) | | (no_of_trans > 25))
(!(grade == 'A'))

Unary negation operator (!)

• Single operand
1. Value is 0 if operand is non-zero
2. Value is 1 if operand is 0

Example

• (4 > 3) && (100 != 200)
1. 4 > 3 is true, so value 1
2. 100 != 200 is true so value 1
3. Both operands 1 for &&, so final value 1
• (!10) && (10 + 20 != 200)
1. 10 is non-0, so value !10 is 0
2. 10 + 20 != 200 is true so value 1
3. Both operands NOT 1 for &&, so final value 0
• (!10) || (10 + 20 != 200)

Same as above, but at least one value non-0, so final value 1

Increment and Decrement Operators

• Both of these are unary operators; they operate on a single operand
• The increment operator causes its operand to be increased by 1
Example: a++, ++count
• The decrement operator causes its operand to be decreased by 1.
Example: i--, --distance

pre-increment v/s post-increment

• Operator written before the operand (++i, --i)
• Called pre-increment operator (also sometimes called prefix ++ and prefix --)
• Operand will be altered in value before it is utilized in the program
• Operator written after the operand (i++, i--)
• Called post-increment operator (also sometimes called postfix ++ and postfix --)
• operand will be altered in value after it is utilized in the program

Relational Operators

• Uses relational and logical operators in addition
• Informally, specifies a condition which can be true or false
• Evaluates to value 0 or 1
1. 0 implies the condition is false
2. 1 implies the condition is true

Relational Operators Symbol & Name

Used to compare two quantities.

Examples:

10 > 20 is false, so value is 0
25 < 35.5 is true, so value is 1
12 > (7 + 5) is false, so value is 0
32 != 21 is true, so value is 1

When arithmetic expressions are used on either side of a relational operator, the arithmetic expressions will be evaluated first and then the results compared a + b > c - d is the same as (a+b) > (c+d).

Bitwise Operators

Note:For calculating two operand with Bitwise operator convert number firstly into binaray number afterthat apply operation on every single bits according to below mention table.

Type Casting

Illustration 3.1
  #include<stdio.h >
    int main() {
    int a = 25, b = 10;
    float result;
    result = a/b;
    printf("The result is %f\n", result);
    return 0;
}
       

        Output:The result is 2.000000
       

• Convert a variable from one data type to another data type
• Cast operator: (type_name) expression

• Implicit casting

• Compiler can implicitly cast the values in an expression based on the declared variable type
• Implicit casting sequence priority:int -> long -> float -> double
• The implicit type for (a*b) is float for below example
int a = 10;
float b = 2.0;
• Rule: The final type of an expression is the highest priority type among all the variable types in the expression

    Illustration 3.2
    #include<stdio.h >
    int main() {
    int a = 55, b = 10;
    float result;
    result = (float) a/b;
    printf("The result is %f\n", result);
    return 0;
    }
          

    output:The result is 5.500000
  

Illustration 3.3
int main() {
int a = 25;
float b = 10.0;
float result;
result = a/b;
printf("The result is %f\n", result);
return 0;
}

        Output:The result is 2.500000
      

Statements in C

Parts of C program that tell the computer what to do

• Different types
• Declaration statements
• Declares variables etc.
• Assignment statement
• Assignment expression, followed by a
• Control statements
• For branching and looping, like if-else, for, while, do-while(to be seen later)
• Input/Output
• Read/print,like printf/scanf

A Special Operator: AddressOf (&)

• Remember that each variable is stored at a location with an unique address
• Putting & before a variable name gives the address of the variable (where it is stored, not the value)
• It Can be put before any variable(with no blank in between)

      int a =10;
      printf("Value of a is %d, and address of a is %d\n", a, &a);
      

Expression Evalation Order of Operator & Associativity Table

Chapter 3 Quiz