Computer system
Computer system
A computer system consists of a computer and supporting devices for input/ output of data.
The basic organization of any computer system shown in the following diagram
Input device --- computer --- out put device
The input device supplies the data, as obtained from us, to the computer. Most commonly used input devices are – teletypewriter, video display unit ( VDU ). We specify the data in a form which we use in our everyday life, that is, in the numeric and alphabetic form. These are converted into the forms which the computer can understand. Data are stored in the computer in the binary form. After the computer has processed the data results are obtained on the output devices. Commonly used devices are printer, VCD and teleprinter. The results obtained are in the human readable form. Computer data is changed into this form by electronic circuits called decoders.
The computer does all the computing data processing work. Its component are :
Arithmetical and logical unit (ALU)
This unit consists of complicated electronic circuits designed using the concepts of boolean algebra. All arithmetical operations- addition, subtraction, multiplication, division and logical operations- comparison, decision, etc, are performed by this unit.
Control unit (CU)
All control unit also consists of electronic circuits. It acts as a supervisor in a computer system. The ALU and the CU are also referred to as central processing unit ( CPU)
Main memory unit (MMU)
This unit store all the data which are to be produced and the program instructions for carrying out the processing computing work. The main memory is also referred to as primary or main storage . It is extremely fast.
Computer memories
The memory unit is an extremely important part of any computer. In the past, commonly used memories were magnetic cores. But now -a- days, all systems use semi- conducting memories. With these, it is possible to have very large and extremely fast memories.
Semi- conductor memory
Semi – conductor memory consists electronic circuits prepared on silicon chips. The electronic circuit is called a flip – flop. A flip- flop is also called a storage cell. Millions of these storage cells can be paired on a single silicon chip. These are two basic types of semi – conductor storage devices. The common type is random access memory ( RAM), while the other is read only memory ( ROM).
RAM
In RAM, information may be read or written into the memory at random. It is volatile memory, that is , information stored in it is lost when the electric power to the circuit is switched off. Normally, user programs & data are stored in RAM.
ROM
Information is written permanently into the ROM. It cannot be changed easily. Data can be read from the ROM, but cannot be written there. It is a non- volatile memory. ROMs are normally used to store information the computer may need to access frequently for its operations.
Besides RAM and ROM , there are other special forms of semi – conducting memories such ad PROM , EPROM, etc. These are used in microcomputer and personal computers for special purposes.
A computer system consists of a computer and supporting devices for input/ output of data.
The basic organization of any computer system shown in the following diagram
Input device --- computer --- out put device
The input device supplies the data, as obtained from us, to the computer. Most commonly used input devices are – teletypewriter, video display unit ( VDU ). We specify the data in a form which we use in our everyday life, that is, in the numeric and alphabetic form. These are converted into the forms which the computer can understand. Data are stored in the computer in the binary form. After the computer has processed the data results are obtained on the output devices. Commonly used devices are printer, VCD and teleprinter. The results obtained are in the human readable form. Computer data is changed into this form by electronic circuits called decoders.
The computer does all the computing data processing work. Its component are :
Arithmetical and logical unit (ALU)
This unit consists of complicated electronic circuits designed using the concepts of boolean algebra. All arithmetical operations- addition, subtraction, multiplication, division and logical operations- comparison, decision, etc, are performed by this unit.
Control unit (CU)
All control unit also consists of electronic circuits. It acts as a supervisor in a computer system. The ALU and the CU are also referred to as central processing unit ( CPU)
Main memory unit (MMU)
This unit store all the data which are to be produced and the program instructions for carrying out the processing computing work. The main memory is also referred to as primary or main storage . It is extremely fast.
Computer memories
The memory unit is an extremely important part of any computer. In the past, commonly used memories were magnetic cores. But now -a- days, all systems use semi- conducting memories. With these, it is possible to have very large and extremely fast memories.
Semi- conductor memory
Semi – conductor memory consists electronic circuits prepared on silicon chips. The electronic circuit is called a flip – flop. A flip- flop is also called a storage cell. Millions of these storage cells can be paired on a single silicon chip. These are two basic types of semi – conductor storage devices. The common type is random access memory ( RAM), while the other is read only memory ( ROM).
RAM
In RAM, information may be read or written into the memory at random. It is volatile memory, that is , information stored in it is lost when the electric power to the circuit is switched off. Normally, user programs & data are stored in RAM.
ROM
Information is written permanently into the ROM. It cannot be changed easily. Data can be read from the ROM, but cannot be written there. It is a non- volatile memory. ROMs are normally used to store information the computer may need to access frequently for its operations.
Besides RAM and ROM , there are other special forms of semi – conducting memories such ad PROM , EPROM, etc. These are used in microcomputer and personal computers for special purposes.
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