1.Computer system
computer operates under the control of instuctions stored in its own memory,which can accept data ,manipulate the data according to specified rules ,produce results ,and store the results for future use.
computer system consists of input devices,output devices ,storage devices,and system unit which is made up by CPU,memory,and other electronics.
2.Information system
Information system consists of hardware ,software,human,procedure,and data.
From data to information :data processing
Information processing cycle:input—process—output—storage
A.Hardware:
input devices&&output devices
System unit:
CPU(central processing uint):can fetch each instruction ,decode the information and excute the information.
There’re tow basic components:central unit and arithmetic-logic unit(CU&&ALU):
ALU:
CU:
Machine cycle:
What’s machine cycle ?
The computer uses addresses to keep track of the characters of data or instructions in main memory.
An address is the location,designated by a unique number,in main memory in which a character of data or part of an instruction is stored during processing.
To process each character ,the processor’s control unit retrieves thar character from its address in main memory and places it into a register.
1.CU(instruction cycle):fetch an instruction from main memory;
decode the instruction and store them;
2.ALU(execute cycle)：executes the instruction(performs the operation on the data);stores the processed results in a register.
Register:
1.Registers are special highspeed circuitry areas that temporarily store data during processing and provide working area for computation.
2.Both CU and ALU countain registers.
3.It could be said that main memory which is outside the processor ,hold material that will be used a little bit later .Registrs,which are contained in the processor ,hold material that is to be processed immediately.
Moterboard:
In a microcomputer ,the motherboard countains the processor chip,the chips for computer memory,and chips that handle basic input and output.
Circuits etched into the motherbourd act like wires ,providing a path so the computer can transport data from one chip to another as needed for processing.
It countains expansion slots that allow you to connect peripheral devices to the computer.
Microprocessor:
1.Is’s an intergrated circuit designed to process instructions.
2.Is’s a very complex integrated circuit,countaining as many as million miniaturized electronic components.
ROM&&RAM:
ROM chips coutain the programs that start the computer ,run system diagnostics,and control lowlevel input and output activities.R
RAM temporarily holds volatile data that is waiting to be processed.
CMOS
CMOS memory contains essential information that is required every time the computer system is turned on.
It is powered by a battery and does not lose its contents when the power is turned off.Its contents can be changed to reflect changes in the computer system such as increase RAMand new hardware devices.
CPU speed is influenced by :Clock rate ,word size ,cache and instruction set size
Word size refers to the number of bits the CPUcan manipulate at one time.
Cache(SRAM)is special high speed memory that gives CPU more rapid access to data.
Output device:
Translates the processed information from the computer into a form that humans can understand.
Input device:
Translates data and programs that humans can understand into a form that the computer can process.
memory:
Holds to data and program instructions for processing data.
wordsize:
This is the number of bits that can be accessed at one time by the CPU.
ROM:
A CPU can only read, or retrieve, programs written on this type of memory chip.
RAM:
This type of memory is volatile, and all data stored in this fashion are lost when the
computer is turned off.
CMOS:It contains essential information that is required every time the computer system
is turned on.
expansion card :
These plug into slots inside the system unit and allow the user to expand the computer’
capabilities .
cache : Memory used to store the most frequently accessed information stored in RAM.
bus: A data roadway between various system components along which bits travel.
B.Software:
1.Category:
System sftware &&Application software
2.Components:
Program,data and document
