UNIT 1:Types of computerNotesMainframe - Larger, powerful, expensive- Multi-user system-used by many people at the same time - Used for processing very large amounts of data- The most po
Trang 1I UNIT 1:
Types of computer Notes
Mainframe - Larger, powerful, expensive
- Multi-user system-used by many people at the same time
- Used for processing very large amounts of data
- The most powerful mainframes are called supercomputers
Minicomputer - Used like mainframe
- Not as big, powerful or expensive as mainframes
- Less common now because microcomputer have improved
Microcomputers or
Personal computers
(PCs)
- The most common type of computer
- Smaller, cheaper, and less powerful than mainframes and minicomputers
Types of portable Notes
Laptop - About the size of a small typewriter
- Less common now because smaller and lighter portable are available
Notebook - About the size of a piece of writing paper
- The most common type of portable Subnotebook - Not quite as big as notebook Can fix into a jacket pocket Handheld or Palmtop - Small enough to fit into the palm of one hand
- Not easy to type with because of their size
- Often used as personal organizers
II UNIT 2:
a ROM and RAM?
- ROM (Read Only Memory): can hold data and programs even when the power in cut and it is used as permanent storage
- RAM (Random Access Memory): all data and programs are last when power supply is cut So it is just used as temporary storage RAM is faster than ROM
b What is computer?
- Computers are electronic machines which can accept data in a certain form, process the data and give the results of the processing in a specified format as information
c 3 basic steps are involved in the process
- First, data is fed into the computer’s memory
- Then, when the program is run, the computer performs a set of instructions and
processes data
- Finally, we can see the results (the output) on the screen or in printed form (see the diagram above)
Trang 2d Software and Hardware.
- Information in the form of data and programs is known as software
- The electronic and mechanical parts that make up a computer system are called hardware
e CPU, Main Memory, Peripherals, Storage devices, Disk drives, Input devices, Output devices
- CPU: Perhaps the most influential component is the central processing unit (CPU) Its function is to execute program instructions and coordinate the activities of all the other units
- Main memory: The main memory holds the instruction and data which are currently being processed by the CPU
- Peripherals: The peripherals are the physical units attached to computer They include storage devices and input/output devices
- Storage devices: Storage devices (floppy, hard or optical disk) provide a permanent storage of both data and programs
- Disk drivers: Disk drivers are used to handle on or more floppy disks
- Input devices: Input devices enable data to go into the computer’s memory The most common input devices are the mouse and the keyboard
- Output devices: Output devices enable us to extract the finished product from the system
f Computer crimes include
1 hacking – unauthorized access to computer system and tampering with other users data
2 pirating, i.e illegally copying and selling programs
3 intentionally attempting to spread viruses
g What is virus
- Viruses are programs that have been written to make a computer be have in an
unexpected and undesired way
h Can viruses be found and removed? How can they be removed?
- Viruses can be found and removed by anti-virus programs, which scan disks and files looking for programming code that is known to be long to particular virus programs
- When a piece of virus code in found, the virus can be identified, and an appropriate program run to delete the virus code from the disk or file
i How to avoid viruses?
- Don’t open email attachments from strangers and take care when down loading files from the website
- Remember also to update your anti-virus software as often as possible
- Becareful to check the virus when using USB
Trang 3III UNIT 3:
a Joy tick
A joystick is another input device you can connect to a computer system The joystick is able to move in eight directions Joysticks are mostly used in computer games to control the way a picture on the screen moves Sometimes two joysticks are connected to a computer so two people can play the games at the same time
b Trackball
A trackball works in exactly the same way as a mouse, except that the ball is on top The user rolls the ball around with her hand to operate it If you use a trackball, you don't need any extra space on your desk to move it around (like you do with a mouse) trackballs are often used on small portable computers and on some video game
machines
c Lightpen
A lightpen can be used to draw pictures directly on to a computer screen or to read the pattern on a barcode A lightpen that can read barcodes detects the difference between the light reflected from a black barcode line and its lighter background
d Scanner
Using a scanner you can input printed drawing, photographs, or text directly into a computer A scanner works like a photocopier - a light is shown on the material and the scanner detects the reflected light You can use a scanner with optical character
recognition (OCR) software to input the scanned text into a word processing package
e Steps in voice input
- Step 1: When you speak, you produce audio waves
- Step 2: A microphone changes these waves into electrical waves
- Step 3: The speech recognition board processes the waves from the microphone to form a binary code for each word you say A binary code is a pattern of zero and ones Each word has its own code
- Step 4: The computer compares the code with other codes in its memory to identify each word
- Step 5: When it finds the correct word it displays it on the monitor screen
f Flatbed scanner and Colour scanner
- Flatbed scanner:
In a flatbed scanner, the paper with the image is placed face down on a glass screen similar to a photocopier Beneath the glass are the lighting and measurement devices Once the scanner is activated, it reads the image as a series of dots and then generates
a digitized image that is sent to the computer and stored as a file The manufacturer usually includes software which offers different ways of treating the scanned image
- Colour scanner:
A colour scanner operates by using three rotating lamps, each of which has a different coloured filter: red, green and blue The resulting three separate images are combined into one by appropriate software
Trang 4g Digital and Film camera
- Digital camera:
Digital camera don’t use film, more expensive to buy than film camera, the cost for each picture is lowes It’s also easy to take a picture, but the quality of digital camera picture
is lower than film camera
- Film camera:
Film camera use film so that cost for each picture is expensive It’s cheaper to buy than digital camera but not easy to take a picture However, the quality of film camera picture are higher than digital camera
IV UNIT 4:
a Three different types of printers:
- Dot-matrix printer:
Dot-matrix printers are the cheapest kind of printer, but their print quality is low and they are slow and noisy They're cheap to run
- Inkjet printer:
Pay a bit more for an inkjet and you get better quality and quieter operation but inkjets are relatively slow and also expensive to run They're good choice for colour
- Laser printer:
A laser printer gives you the best quality of output It prints faster than either of the other two types of printer and it costs less to run than an inkjet It's great for black and white It costs almost twice as much
b Key board:
- Alphanumeric keys: arranged in the same order as a type writer
- Function keys: used by various programs to instruct the PC to perform specific tasks, such as save, copy, cut paste, help,…
- Numeric keypad: set of numeric or editing keys The Num Lock key is used to switch from numbers to editing functions
- Editing keys: cursor and other keys usually used within word processors to page up and down in a long document or to edit text (using Insert or Delete keys)
- Special keys: used to issue commands or to produce alternative characters in key combinations, for example, the Alt key
V UNIT 5:
a Summary of storage devices
Floppies are very cheap, but they are slow and have a limited capacity Hard disks are fast and can store large amounts of data but they are fixed inside the computer, so you cannot use them to transfer data You can transfer data with removable hard disks,
so they are expensive CD-ROM disks can hold quite large amounts of data, however, they are usually read-only because you cannot change the information on them
Magneto-optical disks are like CD-ROMs but you can write data on to them They are removable and have large capacities But they are expensive and do not conform to a standard Therefore they are not very common Magnetic tape is cheap and has a large capacity, but it does not allow random access and drives are very slow For this
reason it is only suitable for backups
Trang 5b Floppy disk:
Most computers use floppy disks Floppies conform to a standard and you can use them
to carry data from one place to another They are also very cheap, but they are slow and have a limited capacity
c Fixed hard disk:
Almost all desktop computers have hard disks They are fast and can store much
greater amounts of data than floppies, but they are fixed inside the computer and you cannot use them to transfer data
d Removable hard disk:
You can move data from place to place using removable hard disks They are almost as fast as fixed hard disks and also have high capacities, but they are relatively expensive They do not all conform to one standard and they are not very common
e CD-ROM disk:
CD-ROM disks are very common and conform to a standard They are removable and can hold large amounts of data They are also cheap to make However, they are
usually read-only You cannot change the information on them They are also slow compared to hard disks
f Magneto-optical disk:
Magneto-optical disks are like CD-ROMs, but you can write data on to them They are removable, have large capacities, and last for a long time, but they are expensive and
do not all conform to one standard For this reason they are not very common
g Magnetic tape:
Magnetic tape is a cheap medium You can use it to store very large amounts of data, but it does not allow random access Every time you read or write a piece of data, you start at the beginning of the tape Tape drives are slow Therefore, it is only suitable for doing backups
VI UNIT 7:
a What is a network?
A network is simply two or more computers linked together It allows users to share not only data files and software applications, but also hardware like printers and other computer resources such as fax
b LAN and WAN
- A network that is connected over a small area - e.g one building – is called a local area network (LAN)
- A network connected over a large area, e.g different buildings, different citis, or even different countries, is known as a wide area network (WAN)
Trang 6c Topology
- Star topology:
A star topology has a server computer at the centre and a separate cable connecting the server to each of the other computers in the network The central server controls the flow of data in the network If the central server fails, the whole network will fail
- Ring topology:
In a ring topology, each computer is connected to its neighbour in a circle The data flows in one direction round the ring If a cable breaks of the computers fails, the whole network will be affected
- Bus topology:
A bus topology has all the computers connected to a common cable The data travels in both directions along the cable If a computer fails or we remove one from the network,
it won't affect the other computers Most networks are usually a combination of star, ring and bus topologies to overcome some of these problems
d Password:
- Password should:
+ be at least 6 characters long
+ have a mixture of numbers and letters
+ have a mixture of capital and small letters
+ be easy to remember
- Password should not:
+ be a word from a dictionary
+ be a common name
+ include space, hyphens, dots, or symbols with a special meaning in computing