第1个回答 2010-01-06
Information literacy
Knowing how to find data from several sources, select relevant material, analyse and organise it into a form that can be used to make decisions.
Computers have become the tools people use to access and manage information.
Information technologists are people who analyse and design the tools.
What is a computer?
Tradition definitions of computers include
• A machine that accepts data and processes it into use information.
• A computer is a binary, digital, electronic, stored program machine.
• While a computer is commonly a digital machine, analogue machine do exist.
An electronic device, operating under the control of instructions stored in its own memory unit, that can accept data (input), process data arithmetically and logically, produce results (output) from the processing and stores results for future use. Many computers receive and send data (communicate) across networks LAN and Wan.
A computer system consists of hardware and software.
What is hardware?
Hardware
Hardware is physical devices or components that can be physically handled – you can thou it.
Input Devices
Input devices convert data that humans collect into coded electrical signals that a computer can process.
The central processing unit
The electronic processing takes place in the CPU. The CPU consists of
• A control unit that controls all of the computer’s functions and an
• Arithmetic and logical unit (ALU) that performs any calculation
Memory
Memory holds all programs and
What is RAM currently open?
Data (notes)
Word processor
O.S
Output devices
Output devices convert the computer’s electronic signals back into information
Secondary storage devices
These devices store programs and data permanently. The programs and data are not necessarily (or likely to be) in current use. E.g. DVD CD
Communication devices
These devices enable a computer to connect to another computer.
List the six different type of hardware?
Secondary storage(external), input, processor, output , memory, Communication.
Name eight pieces of hardware
USB, keyboard, monitor, screen, RAM, ROM, VDU, Modem.
The system unit and peripheral devices
The system unit is the computer box.
Peripheral devices are any devices around the outside, or in other words, plugged into the (back of) the machine. Peripheral devices include the key board, mouse, printer, joy stick and others.
Peripheral devices are any devices around the outside, or in other words, plugged into the (back of) the machine. Peripheral devices include the keyboard, mouse, printer, joy stick and others.
What else does a computer have?
Software
Software is a computer program ,which is a detailed set of instructions that directs a computer to perform the tasks necessary to process data into information. These instructions are written in languages that computer can interpret. Software includes computer games, a word processing packing, an accounting package, amongst
Definition of a computer system
• A computer system is the configuration of hardware and software, functioning together, to process data into useful information, in order to achieve a purpose for a human user.
What is data?
• Data is raw facts, be they numbers, words, images and sounds, that can be input into a computer.
e.g. Mary
a name is a piece of data
What is information?
• Information is processed data, that has meaning and is useful.
e.g. John is a
list of names who scored an A grade on an exam
John A
Chai A
Pam A
e.g. Commodore $23 500
Magna $21 500
Falcon $19 800
The system unit contains the
• Motherboard
• CPU
• Memory
• Other electronics
It is where the computer program instructions are executed and the data is manipulated
The Processor
CPU
The CPU interprets and carries out basic instructions that operate the computer, the CPU contain the
• Control unit and the
• Arithmetic logic unit
Control unit
The control unit directs and coordinates the computer’s operations.
For every single instruction, the control unit repeats four basic operations,
• Fetching
• Decoding
• Executing
• Storing
CPU speed
The CPU’s speed may be measured in MIPS
The number of millions of instructions per second
Arithmetic/logic unit
The ALU performs all calculations, which involve
• Arithmetic operations 2+3
• Comparison operations age>=17
• Logical operations pass
Processing instructions
A CPU may begin executing a second machine cycle before completing the first-referred to as pipelining.
Current CPU’s can pipeline up to 4 instructions.
Storage within the CPU
Registers temporarily hold data and instructions.
The computer’s clock
A System clock is necessary to control the timing of all computer operations.
Each tick of the clock is referred to as a clock cycle.
Clock speed is the speed at which a processor executes instructions.
A hertz is one cycle per second and a megahertz is 1024 by1024 and a gigahertz is 1024 by 1024 by1024.
Memory
Memory is the temporary storage place for data and (program) instructions.
Memory is measured in
• Kilobytes 1024 bytes 2^10
• Megabytes 1024* 1024 bytes 2^20
• Gigabytes 1024*1024*1024 bytes 2^30
Representation of data
Digital computers are built from many small electronic circuits. Each circuit, at any point of time can be turned OFF or ON.
Hence these devices are called two state devices.
Binary Digit 0and 1
Each off or on digital value is called a bit, short for binary digit.
A 1 bit computer would be able to distinguish between two values-characters, symbols or numbers. Hardly sufficient for the characters on the keyboard
Bits Characters
1 2
2 4
3 8
4 16
5 32
6 64
7 128
8 256