Monday, October 26, 2015

TUGAS : MASUKKAN RISALAH DALAM SAMPUL SURAT

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Friday, May 8, 2015

Translator Job

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Maths Questions Solver

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Friday, April 1, 2011

SYSTEM CONCEPT

Define computer system

A Computer System is defined as combination of component designed to process data and store files.


Meaning of input, process,output and storage
1. INPUT 
                  Any data and instructions entered into the memory of a computer. There are 
                  four types of input which are: text, graphics, audio and video.
Example of devices:
Keyboard, mouse, digital camera, joystick, trackball, touch screen, microphone, pointing stick, graphic tablet and scanner, barcode reader.

2. PROCESS
CPU or Central Processing Unit/ Processor/ Microprocessor is an electronic component on a computer’s motherboard that interprets and carries out the basic instructions that operate the computer.
Example of devices:
Intel® Core™2 Duo Processor, AMD Athlon, G4, Mac

3. OUTPUT 
The result of raw input data that has been processed by the Central Processing Unit (CPU) into meaningful information.
Example of devices:
Speaker, monitor, LCD projector, printer and plotter




4. STORAGE 
                  A location in which data, instructions, and information are saved for future
                  use.
Example of devices:


                  CDROM, diskette, hard disk, flash disk.


Describe the information processing cycle which includes ipnut,process, output and storage


Information processing cycle of computer can be well described by the following points:
(1) input, (2) processing, (3) output and (4) storage

  1. Input-entering data into the computer.
  2. Processing-performing operations on the data.
  3. Output-presenting the results.
User will input the data to be processed by the processor.
The storage holds databases, files & programs. The output devices present the processed data as useful information products for the user.

Blog diagram of the information processing cycle















MACHINE CYCLE
Basic operation called Machine Cycle
FETCHING : the process of obtaining a program instruction or data item from memory
DECODING : the process of translating a program instruction into signal that the
computer can execute
EXECUTING : the process of implementing the instructions in a program
STORING : the process of writing the result to the storage or memory

Fetching-Mengambil - proses mendapatkan arahan program atau item data dari memori/ingatan
Decoding- proses menterjemah arahan pogram menjadi isyarat untuk dilaksanakan komputer
Executing-Pelaksanaan -Proses pelaksanaan arahan di dalam sebuah program
Storing-Menyimpan - proses penulisan hasil untuk simpanan atau memori

Data presentation

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 b 
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 combinations 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.

Introduction to BINARY CODING

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.

State the unit of data measurement

1
Bit
Single Binary Digit (1 or 0)
2
Byte
1 Byte = 8 bits
3
Kilobyte (KB)
1 KB = 1024 bytes or 1 KB = 10 bytes
4
Megabyte
1 MB = 1 048 576 bytes or 1 MB = 20bytes
1 MB = 1024 KB
5
Gigabyte
1 GB = 1 073 741 824 bytes or 1 GB = 230 bytes
6
Terabyte (TB)
1 TB = 1 099 511 627 776 bytes or 1 TB =40 bytes




State the units of clock speed measurement

When we hear about a computer’s ‘speed’, they mean how fast it can
process data. In other words, this means the speed that the computer can
turn data into information.
Every microprocessor contains a system clock. The system clock controls the speed of
all the operations within a computer.The speed of the clock in measured by how many
cycles per second the clock makes.

MEGAHERTZ (MHz)
Mega is prefix that stands for million. Example àone computer that operates at 933 MHz
has 933 million clock cycles in one second.

GIGAHERTZ (GHz)
Giga is prefix that stands for billion 1 GHz equal to one billion cycles of the system clock
For example, a microprocessor that runs at 200 GHz executes 200 billion cycles per
second. This is what they a talking about if they say a computer is a 2.4 GHz machine.
Its clock rate is 2.4 billion cycles per second.In relation with megahertz, 1.0 GHz is 
equivalent to 1000 MHz. GHz is most often used as a measurement of a pc processor
chip & power, with bigger numbers meaning more speed and higher price

Hertz & Second
The clock speed unit is measured in hertz.
1 Hertz =121 cycle1 second"> 1 cycle / 1 se

1 Megahertz (MHz) = 1,000,000 cycles / 1 second 121,000,000 cycles1 second">
1 GHz = 1,000,000,000 cycles / 1 second 121,000,000,000 cycles1 second">
1 GHz = 1 000 MHz

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 hackers, crackers and script kiddie.
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.

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. 

c) NETWORK SECURITY The transfer of data through network has become a common practice and the need to implement network security has become significant. 
PERSONAL COMPUTER SECURITY CHECKLISTIn 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

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

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

e) WORM• a program that copies and spreads itself through a network

Primary Differences Between Worms And viruses
Worm and VirusWorm operates through the network.Virus spreads through any medium.
Worm spreads copies of itself as a standalone program.Spreads copies of itself as a program that attaches to other programs.


HACKERHacking 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.

NATURAL AND ENVIRONMENTAL THREATSComputers 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

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

SECURITY MEASURES

Security measures means the precautionary measures taken towards possible danger or damage. There are 6 types of security measures.


1) DATA BACKUP
Data Backup is a program of file duplication. Backups of data applications are necessary so that they can be recovered in case of an emergency.



2) CRYPTOGRAPHY
Cryptography is a process of hiding information by altering the actual information into different representation, for example, an APA can be written as I? X. Almost all cryptosystems depend on a key such as a password like the numbers or a phrase that can be used to encrypt or decrypt a message.The traditional type of cryptosystem used on a computer network is called a symmetric secret key system.



3) ANTIVIRUS
An antivirus program protects a computer against viruses by identifying and removing any computer viruses found in the computer memory, on storage media or incoming e-mail files. An antivirus program scans for programs that attempt to modify the boot program, the operating system and other programs that normally are read from but not modified.



IDENTIFYING VIRUS
Two technique are used to identify the virus.



If an antivirus program identifies an infected file, it attempts to remove its virus, worm or Trojan horse. If the antivirus program cannot remove the infection, it often quarantines the infected file. Quarantine is a separate area of a hard disk that holds the infected file until the infection can be removed. This step ensures other files will not become infected. Patents for inventions Utility, design or plant patents that protect inventions and improvements to existing inventions



4) ANTI-SPYWARE
Spyware is a program placed on a computer without the user’s knowledge. It secretly collects information about the user.The spyware program communicates information to the outside source.An anti-spyware application program sometime called tracking software or a spybot is used to remove spyware.



Among of the popular anti-spyware programs are:
• Spybot Search and Destroy
• Ad-aware
• Spyware Blaster



5) FIREWALL
Firewall is a piece of hardware or software which functions in a networked environment to prevent some communications forbidden by the security policy.Firewall implement a security policy. It might permit limited access from in or outside the network perimeters or from certain user or for certain activities.


6) HUMAN ASPECTS OF SECURITY MEASURES

Human aspects refer to the user and also the intruder of a computer system.
It is one of the hardest aspects to give protection to.The most common problem is the lack of achieving a good information security procedure