CSC 103

Lecture 5

Introduction to Computers and Programming

Evaluate yourself!

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Point out the errors, if any, in the following C statements:

(a) int = 314.562 * 150 ;

(b) name = ‘Ajay’ ;

(c) varchar = ‘3’ ;

(d) 3.14 * r * r * h = vol_of_cyl ;

(e) k = ( a * b ) ( c + ( 2.5a + b ) ( d + e ) ;

(f) m_inst = rate of interest * amount in rs ;

Operators

Operators are symbols that can be used to perform certain calculations. They are always in between expressions.

Operators can be classified according to The number of their operands Unary (one operand)

Binary (two operands)

The type of their operands and of their output Arithmetic

Relational

Logical

Bitwise

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Assignment operator: =

Binary operator used to assign a value to a variable.

Its left operand is the destination variable

Its right operand is an expression.

int var;

var = 10;

COPY

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Arithmetic operators

They operate on numbers and the result is a number.

The type of the result depends on the types of the operands.

If the types of the operands differ, one is "promoted" to other.

The "smaller" type is promoted to the "larger" one. char int float double

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Arithmetic operators: +, *

+ is the addition operator

* is the multiplication operator

They are both binary

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Arithmetic operator:

This operator has two meanings:

subtraction operator (binary)

negation operator (unary)

e.g. 31 - 2

e.g. -10

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Arithmetic operator: /

Division operator

CAREFUL! The result of integer division is an integer:

e.g. 5 / 2 is 2, not 2.5

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Arithmetic operator: %

The modulus (remainder) operator.

It computes the remainder after the first operand is divided by the second

works only with integers

It is useful for making cycles of numbers: For an int variable x :

if x is: 0 1 2 3 4 5 6 7 8 x%3 is: 0 1 2 0 1 2 0 1 2

e.g. 5 % 2 is 1,

6 % 2 is 0

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An Example

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#include <stdio.h>

void main (void)

{

int a = 25, b = 5, c = 10, d = 7;

printf ("a %% b = %i\n", a % b);

printf ("a %% c = %i\n", a % c);

printf ("a %% d = %i\n", a % d);

printf ("a / d * d + a %% d = %i\n",

a / d * d + a % d);

}

Output: a % b = 0 a % c = 5 a % d = 4 a / d * d + a % d = 25

Using Arithmetic Operators

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#include <stdio.h> void main (void) { int a = 100, b = 2, c = 25, d = 4,result; result = a - b; // subtraction printf ("a - b = %i\n", result); result = b * c; // multiplication printf ("b * c = %i\n", result); result = a / c; // division printf ("a / c = %i\n", result); result = a + b * c; // precedence printf ("a + b * c = %i\n", result); printf ("a * b + c * d = %i\n", a * b + c * d); }

Output:

a - b = 98

b * c = 50

a / c = 4

a + b * c = 150

a * b + c * d = 300

Relational operators

These perform comparisons and the result is what is called a Boolean: a value TRUE or FALSE

FALSE is represented by 0; anything else is TRUE The relational operators are:

< (less than) <= (less than or equal to) > (greater than) >= (greater than or equal to) == (equal to) != (not equal to)

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Logical operators

These have boolean operands and the result is also a boolean.

The basic boolean operators are:

&& (logical AND)

|| (logical OR)

! (logical NOT) -- unary

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Special assignment operators

write a += b; instead of a = a + b;

write a -= b; instead of a = a - b;

write a *= b; instead of a = a * b;

write a /= b; instead of a = a / b;

write a %= b; instead of a = a % b;

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Special assignment operators Increment, decrement operators: ++, --

Instead of a = a + 1 you can write a++ or ++a

Instead of a = a - 1 you can write a-- or --a

What is the difference?

num = 10;

ans = num++;

num = 10;

ans = ++num;

First increment num,

then assign num to ans.

In the end,

num = 11

ans = 11

First assign num to ans,

then increment num.

In the end,

num =11

ans = 10

post-increment pre-increment

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Operator Hierarchy

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This expression

z = a * b + c / d is same as;

z = (a * b) + (c / d)

Solve Following Expressions;

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&

Solution

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In C Language

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Associativity of Operators

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We can have same priority operators in an expression

Then we check associativity of operators

There are two rules:

Left to Right means that the operators are performed from left to right

Right to Left means that the operators are performed from right to left