Download Recitation 1

CS 007: Introduction to
Computer Programming
Ihsan Ayyub Qazi
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Who am I, and Who are You?
Who am I?
2nd Year PhD Student in the CS Dept
Did my undergrad in CS and MATH
Research Interests
Computer Networks and Distributed Systems
Other interests
Sports (Volleyball, Racket Ball etc)
Who are you, and what do you do?
Introductions…
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Other Information
Office: 6803 SENSQ
Email: [email protected]
Office Hours:
Wed 2:30PM - 5:40PM (10 min break)
or by appointment
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Agenda for Today’s class
Review
Exercises
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Recall: Goals of the Course
To write computer programs in Java
To
recognize and create
well-written
Set of (computer understandable)
A programming language
instructions to perform
a task or
a
programs
in
good
programming
style
set of tasks
Hands-on experience with several
stages of the life-cycle of a computer
program, including planning,
implementation, and debugging
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Example Java Program
public class Number
{
public static void main(String [] args)
{
int age = 25;
int height = 75;
int sum = age + height;
}
}
Punctuation
Key Words Names
Programmer-Defined
Syntax
Operator
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Last Time..
// This is a simple Java program.
public class Hello
{
public static void main(String [] args)
{
System.out.println(“Hello World”);
}
}
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Compiling and Running
HelloWorld.java
javac HelloWorld.java
compile
source code
run
java HelloWorld
HelloWorld.class
bytecode
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Variables
 In a computer program a variable is a named storage
location in the computer’s memory. Each variable has a
type and a name
 A variable should be declared and initialized
 Variable Declaration:
 char a;
 char is the variable type and a is the variable name
 Variables must be declared before they can be used
 Variable Initialization:
 a = ‘z’; // Assigning value to a variable
 The equal sign is an operator that stores the value on its
right into the variable named on its left.
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Primitive Data Types Java
Data Type
Description
Boolean
true or false
char
A character
int
Integer
(4 bytes)
short
(2 bytes)
Short integer
long (8 bytes)
Long integer
float
Single precision floating point
(4 bytes)
Double (8 bytes) Double precision floating point
byte (1 byte)
limited range (Integer)
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What Is A Byte?
 The smallest data unit in a computer is a bit (1
or 0)
 8 bits are called a byte
 Computers store numbers in binary
0 = 0 in binary
1 = 1 in binary
2 = 10 in binary
3 = 11 in binary
4 = 100 in binary
 Difference between counting using decimal
umbers and binary numbers
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Special Cases
float number = 23.5; ERROR
float number = 23.5f; CORRECT
float number = 23.5F; CORRECT
 long bigNumber = 9223372036854775807; ERROR
 long bigNumber = 9223372036854775807L; CORRECT
 long bigNumber = 9223372036854775807l;CORRECT
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The boolean Data Type
 a boolean variable can have two values:
true
false
 Example:
boolean bool;
bool = true;
System.out.println(bool);
bool = false;
System.out.println(bool);
true
false
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The char Data Type
 used to store characters
 character literals are enclosed in single
quotes
 Example:
char letter;
A
letter = 'A';
b
System.out.println(letter);
letter = ‘b';
System.out.println(letter);
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The char Data Type
Characters are internally represented
by numbers.
Java uses Unicode which is a set of
numbers that are used as codes for
representing characters
Example: 65 is the code for A, 66 is the code
for B
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The char Data Type
 variables of char type can be defined using
either literal characters or their
corresponding numeric codes
Example:
char letter;
letter = 65;
System.out.println(letter)
letter = 66;
System.out.println(letter);
A
B
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Arithmetic operators
Operator
Meaning
Type
Example
+
Addition
Binary total = cost+tax;
-
Subtraction
Binary cost = total-tax;
*
Multiplication Binary Tax = cost*rate;
/
Division
Binary saleprice=original/2;
%
Modulus
Binary remainder=value%3;
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The % Operator
Returns the remainder of a division
operation involving two integers
Common operation in computer science
Examples;
4%5 is 4
30%6 is 0
22%7 is 1
3205%100 is 5
3205%10 is 5
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Operator Precedence
1. Evaluate – (unary negation) from right
to left
2. Evaluate * / % from left to right
3. Evaluate + - from left to right
 Note: If equal precedence, evaluate
from left to right except for
negations where we evaluate from
right to left
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Precedence Examples
Polynomial = 1+2*3+ 6/2 – 2;
Polynomial has the value of 1+6+3-2=8
Polynomial = –1 + 5 – 2; // 2
Polynomial = –(–3) + –(–5); //8
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Grouping With Parentheses
You can use parentheses to force the
evaluation of enclosed operations
before others
Examples:
x * ( y + z*z ) instead of x*y + z*z
x * ( y * ( z + 165 ) + 85 ) – 65
Average = (a +b +c ) /3;
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The Math class
value = Math.pow(x,y); // now value
holds x to the power of y
value = Math.sqrt(x); //now value holds
the square root of x
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Combined Assignment Operators
+=
x += 1;
x = x + 1;
–=
x –= 1;
x = x – 1;
*=
x *= 1;
x = x * 1;
/=
x /= 1;
x = x / 1;
%=
x %= 1;
x = x % 1;
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Exercise 1: Swap the values of two
integers
 public class Swap{
public static void main (String args [])
{
 int x, y, z;
 x = 5;
 y = 8;
 System.out.println("x="+x+" y="+y);
 z = x;
 x = y;
 Y = z;
 System.out.println("x="+x+" y="+y);
}
}
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Exercise 2: Compute the average and
Standard Deviation of three numbers
Note: Make use of Math.pow() and
Math.sqrt()
Assume
double x = 4.0
double y = 5.0
double z = 6.0
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Solution
 public class Multiply{
 public static void main (String args [])
 {

double x=4.0, y=5.0, z=6.0;

double av, sd;


av = (x+y+z)/3.0;

sd = Math.pow((x-av),2) + Math.pow((y-av),2) + Math.pow((z-av),2);

sd = sd/3.0;

sd = Math.sqrt(sd);


System.out.println("Average = "+av);

System.out.println("Standard Deviation = "+sd);
 }
 }
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Exercise 3: Determining Prime
Numbers
 Assume that you are given numbers 5,6,…10
 Determine which of them are prime
 A prime number is a positive integer p>1 that has no
positive integer divisors other than 1 and p itself
 Hint:
 Use % (modulus) operator
 For each number p compute
 p % 2, p % 3,…, p % (p-1)
 Examples
5%1=0
5%2=1
7%6=1
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Thanks !!
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