Data Measurement

Why is 1024 bytes = 1KB?

KILOBYTE (KB)
In mathematics, 1 KB = 1000 bytes.
In computer, 1 KB = 1024 bytes or
can be said as:

This is how we get the calculation for 1024 bytes.

MEGABYTE (MB)
1 MB = 1 048 576 bytes or it can be said as:

GIGABYTE (GB)
1 GB = 1 073 741 824 bytes or it can be said as:

1 GB = 230 bytes

TERABYTE (TB)
1 TB = 1 099 511 627 776 bytes or it can be said as:

1 TB = 240 bytes

1 byte = 8-bits

Data Representation

BINARY DIGIT

Computers recognize only two discrete states: on and off. These states can be represented by two digits, 0 and 1. Each 0 or 1 is called a bit in the binary system.




Bit is the smallest unit of data a computer can process. Bit is a short for binary digit. The binary system has a base of 2 with the two digits (0 and 1). Combinations of 0s and 1s represent larger numbers.

BIT

A bit is the smallest unit of data that the computer can process. Bit is a short for binary digit. A bit is represented by the numbers 1 and 0. These numbers represent the binary system. They correspond to the states of on and off, true and false, or yes and no. All digital data use the binary system to process the information. This information include letters, digits or special character.

BYTE

• Byte is a unit of information built from bits. One byte is equals to 8 bits. Eight bits that are grouped together as a unit. A byte provides enough different combinations of 0s and 1s to represent 256 individual characters.

• One byte represents a single character such as the number 3, letter or a $ symbol. Bits and bytes are the basis for representing all meaningful information and programs on computers.

CHARACTER

8 bits = 1 byte

One byte represents one character such as A, 7, 9 and +.Eight bits that are grouped together as a unit. A byte provides enough different combination of 0s and 1s to represent 256 individual characters.
For example, the capital letter F is represented by the binary code 01000110 that can be understood by the computer system. Eight bits grouped together as a unit are called a byte. A byte represents a single character in the computer.

CHARACTER CODES

There are three character codes to represent characters which are ASCII, EBCDIC and Unicode. Each byte contains eight bits. A byte provides enough different combination of 0s and 1s to represent 256 characters.

The combinations of 0s and 1s are defined by patterns. These patterns are called coding scheme. The 256-character capability of ASCII and EBCDIC is too small to handle the characters that are used by other languages such as Arabic, Japanese and Chinese.

The Unicode coding scheme is designed to solve this problem. It uses two bytes (16 bits) to represent one character. Unicode will have more than 65,000 different characters. This can cover all the world’s languages.

Clock Speed Measurement

EVOLUTION OF COMMUNICATION

When people talk about a computer’s “speed”, they mean how fast it can process data. In other words, this means the speed the computer can turn data into information.

Enjoy this video!!

Every microprocessor contains a system clock. The system clock controls the speed of all the operations within a computer. The speed of the clock is measured by how many cycles per second the clock makes.

HERTZ AND SECONDS ---::> The clock speed unit is measured in hertz. A hertz is one cycle per second.

MEGAHERTZ (MHz) :::::> Mega is a prefix that stands for million. Thus, megahertz (MHz) equals to one million cycles of the system clock. A computer that operates at 933 MHz (megahertz) has 933 million clock cycles in one second.

GIGAHERTZ (GHz)

• Giga is a prefix that stands for billion.Gigahertz (GHz) equals to one billion cycles of the system clock.In relation with megahertz,1.0 GHz is equivalent to 1000 MHz.
• For example, a microprocessor that runs at 200 GHz executes 200 billion cycles per second. This is what they are talking about if they say a computer is a 2.4 GHz machine. Its clock rate is 2.4 billion cycles per second.
• GHz is most often used as a measurement of a PC processor chip and power, with bigger numbers meaning more speed and higher price.

PROCESSING SPEED

The system clock is one of the major factors that influence the computer speed. A CPU with a higher clock speed can process more instructions per second than a CPU with a lower clock speed. For example, a 1 GHz CPU is faster than a CPU operating at 800 MHz. The speed of the system clock affects only the CPU. It has no effect on peripherals such as a printer or disk drive.

MICROPROCESSOR SPEED

1. One way of comparing the performance of personal computers is by comparing their microprocessor speeds. Microprocessor speeds are determined by their clock speed and are usually expressed in gigahertz (GHz), billion of machine cycles per second.
2. For example, a personal computer that is listed at 2.2 GHz has a processor capable of handling 2.2 billion machine cycles per second. A top speed personal computer can be much faster, with newer ones exceeding 3.0 GHz.
3. Direct comparison of clock is meaningful between identical microprocessor.
4. Thus, it is accurate to say that a Pentium 4 running at 2.4 GHz is approximately one-third faster than a Pentium 4 running at 1.8 GHz.

SPEED AND PATH

The combination of speed and number of paths determines the total processing speed or channel bandwidth. This is because different processors often use different architectures. For this reason, a 1.4 GHz Pentium 4 performs better than a 1.4 GHz Pentium 3, but it is not as fast as a 1.4 GHz Power PC G4 processor.

Introduction to Binary Coding

COMMUNICATION CODES

1. Smoke signals, Morse code and semaphore are some of the communication codes used by people in the early days. In the information digital era, people send information via electronic devices such as through the computers.

1. Computers use binary codes to communicate. One of the widely used binary codes is the American Standard Code for Information Interchange (ASCII).

HISTORY OF CHARACTER CODES

Before people used binary codes such as ASCII to communicate via computers, character codes were widely used as a medium of communication. Let’s look at some of the character codes used prior to the use of ASCII.

WHAT IS ASCII?

• ASCII pronounced as "ask-key" stands for the American Standard Code for Information Interchange and was proposed by ASA (American Standard Association) in 963 and was finalised in 1968.ASCII is a standard of 7-bit code used to represent characters, which include letters, numbers and punctuation marks.

• 7 bits allow the computer to encode a total of 128 characters for the numbers 0-9, uppercase and lowercase letters A-Z and a few punctuation symbols. However this 128 bit code only suitable for english language speaking users.
  
• IBM and Apple expanded the amount of space reserved for the character codes to 8-bits, equivalent to 1 byte.

FUNCTIONS OF ASCII
ASCII was established to achieve compatibility between various types of data processing equipment making it possible for the components to communicate with each other successfully.

ASCII enables manufacturers to produce components that are assured to operate correctly in a computer.

ASCII makes it possible for humans to interact with a computer. It also enables users to purchase components that are compatible with their computer configurations.


HOW ASCII WORKS IN A COMPUTER SYSTEM?

When you press a key, for example the letter D on your keyboard, the electronic signal is sent to the CPU for the computer to process and store in memory. Every character is converted to its corresponding binary form. The computer the processes the letter as a byte., which actually a series of on and off of electrical states. When the computer is finished processing the byte, the software installed in the system convert the byte back which is then displayed in the screen. In this example, the letter D is converted to 01000100.

Computer Security

DEFINITION OF COMPUTER SECURITY
Computer security means protecting our computer systems and the information they contain against unwanted access, damage, destruction or modification.

We need to protect our computer from any intruders such as hack

ers, crackers and script kiddie.
We do not want strangers to read our e-mail, use our computer to
attack other systems, send forged e-mail from our computer, or examine personal information stored on our computer such as financial statements.

TYPES OF COMPUTER SECURITY
Three types of computer security are:

a) hardware security b) software security/data security c) network security

a) HARDWARE SECURITY
Hardware security refers to security measures used to protect the hardware specifically the computer and its related documents. The examples of security measures used to protect the hardware include PC-locks, keyboard-locks, smart cards and biometric devices.

PC-Lock

Keyboard-Lock

Smart Card

Biometric devices

b) SOFTWARE AND DATA SECURITY
Software and data security refers to the security measures used to protect the software and the loss of data files. Examples of security measures used to protect the software are activation code and serial number. An example of security measure used to protect the loss of data files is the disaster recovery plan method. The idea of this plan is to store data, program and other important documents in a safe place that will not be affected by any major destruction.

Data Recovery Plan

c) NETWORK SECURITY
The transfer of data through network has become a common practice and the need to implement network security has become significant. Network security refers to security measures used to protect the network system. One example of network security measures is firewall. With firewall, network resources can be protected from the outsiders.

PERSONAL COMPUTER SECURITY CHECKLIST

In order to make sure our computers are secured, here are the computer

security checklist to follow.

- Do not eat, drink or smoke near the computer
- Do not place the computer near open windows or doors
- Do not subject the computer to extreme temperatures

- Clean the equipment regularly
- Place a cable lock on the computer
- Use a surge protector
- Store disks properly in a locked container

- Maintain backup copies of all files
- Stores copies of critical files off sites
- Scan a floppy disk before you open it
- Do not open any unknown email received

Primary Differences Between Worms And viruses

Let's watch a video before we go further.....

Worm

• Operates through the network
• Spreads copies of itself as a standalone program

Virus

• Spreads through any medium
• Spreads copies of itself as a program that attaches to other programs

HOPE YOU ENJOY THIS!!



THEFT
Two types of computer theft:

1) Computer is used to steal money, goods, information and resources.
2) Stealing of computer, especially notebook and PDAs.

Three approaches to prevent theft:

1) Prevent access by using locks, smart-card or password
2) Prevent portability by restricting the hardware from being moved
3) Detect and guard all exits and record any hardware transported

Introduction to Computer Threats

The computer is a great tool to store important information. In certain cases, the information is very vital that losing it will harm the computer system.

Computer threats can come from many ways either from human or natural disasters. For example, when someone is stealing your account information from a trusted bank, this threat is considered as a human threat. However, when your computer is soaked in heavy rain, then that is a natural disaster threat.



MALICIOUS CODE

Malicious code is also known as a rogue program. It is a threat to computing assets by causing undesired effects in the programmer’s part. The effect is caused by an agent, with the intention to cause damage.

The agent for malicious code is the writer of the code, or any person who causes its distribution. There are various kinds of malicious code. They include virus, Trojan horse, logic door, trapdoor and backdoor, worm and many others.

a) VIRUS
· a program that can pass on the malicious code to other programs by modifying them
· attaches itself to the program, usually files with .doc, .xls and .exe extensions
· destroys or co-exists with the program
· can overtake the entire computing system and spread to other systems


b) TROJAN HORSE
· a program which can perform useful and unexpected action
· must be installed by users or intruders before it can affect the system’s assets
· an example of a Trojan horse is the login script that requests for users’ login ID and password
· the information is then used for malicious purposes


c) LOGIC BOMB
· logic bomb is a malicious code that goes off when a specific condition occurs.
· an example of a logic bomb is the time bomb
· it goes off and causes threats at a specified time or date


e) TRAPDOOR OR BACKDOOR
· a feature in a program that allows someone to access the program with special privileges

f) WORM
· a program that copies and spreads itself through a network


HACKER

Hacking is a source of threat to security in computer. It is defined as unauthorised access to the computer system by a hacker.Hackers are persons who learn about the computer system in detail. They write program referred to as hacks. Hackers may use a modem or cable to hack the targeted computers.

How Hacker Attack Your PC??

NATURAL AND ENVIRONMENTAL THREATS
Computers are also threatened by natural or environmental disaster. Be it at home, stores, offices and also automobiles.Examples of natural and environmental disasters:
- Flood
- Fire
- Earthquakes, storms and tornados
- Excessive Heat
- Inadequate Power Supply

Computer Hardware

Hardware refers to the equipment associated with the computer system for examples monitor and keyboard.

Computer System consists of four major hardware component :

1. Input devices

Input devices. From Left: microphone, joystick, videocam, mouse and keyboard.

When data is entered into the computer system, it is called an input. Input comes in various text, graphic, audio and video. Input devices are needed to input data into the computer system.




2. Processor

Random Access Memory (RAM)

The system’s primary storage, Random Access Memory (RAM) can only hold data temporarily.

3. Output Devices

• Output is the result of raw input data that has been processed by the Central Processing Unit (CPU) into meaningful information
• Common forms of output are text, graphic, audio, video and animation

4. Storage

• Storage is a location which data, instruction and information a held for future use
• Every computer uses storage to hold system software and application software
• A storage medium also called secondary storage is the physical material in the computer that keep data, instruction and information

System Concept

• A computer system is defined as combination of components designed to process data and store files.
  
• A computer system consists of four major hardware components; input devices, output devices, processor and storage devices.
• A computer system requires hardware, software and a user to fully function.

Information Processing Cycle