13-02-2013, 02:22 PM
Explain the functional units of a basic computer with a neat diagram.
[attachment=50696]
CPU: This is the computational unit and is the computer's heart. This entity controls the operations of the computer and performs its data processing functions. It is usually referred to as a processor. All the actions of all components are controlled by the control unit of CPU.
CPU comprises two units called Arithmetic Logic Unit (ALU), where all the arithmetic and logical operations are performed and the Control Unit (CU) which coordinates with all other units for proper system
operation.
•Memory: Memory is used to store the instructions, data and the result as well. Memory unit is an integral part of a computer system. The main function of a memory unit is to store the information needed by the system.
Input/output interface: They are used to move data from the computer and from its external environment. The external environment may be an input or an output device like Printer, displays, keyboard etc.
•System interconnection: This constitutes some mechanism that provide for communication among CPU, Memory & I/O. These can be referred to as a system BUS. Traditionally the computer system consists of a single CPU. But some machines like multiprocessing involves the use of multiple CPU’s and share a single memory.
Central Processing Unit
Its major structural components are Control unit, ALU, Registers and CPU
interconnections.
Arithmetic logic unit (ALU)
The ALU is a collection of logic circuits designed to perform arithmetic (addition, subtraction, multiplication, and division) and logical operations (not, and, or, and exclusive-or). It's basically the calculator of the CPU. When an arithmetic or logical operation is required, the values and
command are sent to the ALU for processing.
•Control Unit:
The purpose of control unit is to control the system operations by routing the selected data items to the selected processing hardware at the right time. Control unit acts as nerve centre for the other units.
•Instruction decoder:
All instructions are stored as binary values. The instruction decoder receives the instruction from memory, interprets the value to see what instruction is to be performed, and tells the ALU and the registers which circuits to energize in order to perform the function.
•Registers:
The registers are used to store the data, addresses, and flags that are in use, by the CPU.
Memory Units
Memory is basically a large array of bytes. The main function of a memory unit is to store the information needed by the system. Information stored can be data, an instruction that is nothing but programs and may be some garbage. Memory system of a computer can be broadly classified into four groups.
•Internal Memory
Internal memory refers to a set of CPU registers. These serve as working memory, storing temporary results during the computation process. They form a general purpose register file for storing the data as it is processed. Since the cost of these registers is very high only few registers can be used in the CPU.
•Primary Memory
Primary memory is also called as main memory, which operates at electronic speeds. CPU can directly access the program stored in the primary memory. Main memory consists of a large number of semiconductor storage cells. Each cell is capable of storing one bit of information. Word is a group of these cells. Main memory is organized so that the contents of one word, containing n bits, can be stored or retrieved in one basic operation.
•Secondary Memory
This memory type is much larger in capacity and also much slower than the main memory. Secondary memory stores system programs, large data files and the information which is not regularly used by the CPU. When the capacity of the main memory is exceeded, the additional
information is stored in the secondary memory. Information from the secondary memory is accessed indirectly through the I/O programs that transfer the information between the main memory and secondary memory. Examples for secondary memory devices are magnetic hard
disks and CD-ROMs.
•Cache Memory
The performance of a computer system will be severely affected if the speed disparity between the processor and the main memory is significant. The system performance can be improved by placing a small, fast acting buffer memory between the processor and the main memory.
This buffer memory is called as cache memory. Cost of this memory is very high.
Input Devices:
Computer accepts the coded information through the input unit. It has the capability of reading the instructions and data to be processed. The most commonly used input device is the keyboard of a video terminal. This is electronically connected to the processing part of a computer. The keyboard is wired such that whenever a key is pressed the corresponding letter or digit is automatically translated into its corresponding code and is directly sent either to memory or the processor.
Output Devices
Output unit displays the processed results. Examples are video terminals and graphic displays.
I/O devices do not alter the information content or the meaning of the data. Some devices can be used as output only e.g. graphic displays. Following are the Input / Output techniques
o Programmed Interrupt driven
o Direct Memory Access (DMA)
System Interconnection / BUS
“A bus is a communication pathway connecting two or more devices.” A key characteristic of a bus is that it is a shared transmission medium. Multiple devices connect to the bus, and a signal transmitted by any one device is available for reception by all other devices attached to the bus. If two devices transmit during the same time period, their signals will overlap and
become garbled. Thus, only one device at a time can successfully transmit. The communication between the external environment and CPU is established through the System Bus. System bus is classified into three different types, depending on whether it carries Data, Control, or Address
information
[attachment=50696]
CPU: This is the computational unit and is the computer's heart. This entity controls the operations of the computer and performs its data processing functions. It is usually referred to as a processor. All the actions of all components are controlled by the control unit of CPU.
CPU comprises two units called Arithmetic Logic Unit (ALU), where all the arithmetic and logical operations are performed and the Control Unit (CU) which coordinates with all other units for proper system
operation.
•Memory: Memory is used to store the instructions, data and the result as well. Memory unit is an integral part of a computer system. The main function of a memory unit is to store the information needed by the system.
Input/output interface: They are used to move data from the computer and from its external environment. The external environment may be an input or an output device like Printer, displays, keyboard etc.
•System interconnection: This constitutes some mechanism that provide for communication among CPU, Memory & I/O. These can be referred to as a system BUS. Traditionally the computer system consists of a single CPU. But some machines like multiprocessing involves the use of multiple CPU’s and share a single memory.
Central Processing Unit
Its major structural components are Control unit, ALU, Registers and CPU
interconnections.
Arithmetic logic unit (ALU)
The ALU is a collection of logic circuits designed to perform arithmetic (addition, subtraction, multiplication, and division) and logical operations (not, and, or, and exclusive-or). It's basically the calculator of the CPU. When an arithmetic or logical operation is required, the values and
command are sent to the ALU for processing.
•Control Unit:
The purpose of control unit is to control the system operations by routing the selected data items to the selected processing hardware at the right time. Control unit acts as nerve centre for the other units.
•Instruction decoder:
All instructions are stored as binary values. The instruction decoder receives the instruction from memory, interprets the value to see what instruction is to be performed, and tells the ALU and the registers which circuits to energize in order to perform the function.
•Registers:
The registers are used to store the data, addresses, and flags that are in use, by the CPU.
Memory Units
Memory is basically a large array of bytes. The main function of a memory unit is to store the information needed by the system. Information stored can be data, an instruction that is nothing but programs and may be some garbage. Memory system of a computer can be broadly classified into four groups.
•Internal Memory
Internal memory refers to a set of CPU registers. These serve as working memory, storing temporary results during the computation process. They form a general purpose register file for storing the data as it is processed. Since the cost of these registers is very high only few registers can be used in the CPU.
•Primary Memory
Primary memory is also called as main memory, which operates at electronic speeds. CPU can directly access the program stored in the primary memory. Main memory consists of a large number of semiconductor storage cells. Each cell is capable of storing one bit of information. Word is a group of these cells. Main memory is organized so that the contents of one word, containing n bits, can be stored or retrieved in one basic operation.
•Secondary Memory
This memory type is much larger in capacity and also much slower than the main memory. Secondary memory stores system programs, large data files and the information which is not regularly used by the CPU. When the capacity of the main memory is exceeded, the additional
information is stored in the secondary memory. Information from the secondary memory is accessed indirectly through the I/O programs that transfer the information between the main memory and secondary memory. Examples for secondary memory devices are magnetic hard
disks and CD-ROMs.
•Cache Memory
The performance of a computer system will be severely affected if the speed disparity between the processor and the main memory is significant. The system performance can be improved by placing a small, fast acting buffer memory between the processor and the main memory.
This buffer memory is called as cache memory. Cost of this memory is very high.
Input Devices:
Computer accepts the coded information through the input unit. It has the capability of reading the instructions and data to be processed. The most commonly used input device is the keyboard of a video terminal. This is electronically connected to the processing part of a computer. The keyboard is wired such that whenever a key is pressed the corresponding letter or digit is automatically translated into its corresponding code and is directly sent either to memory or the processor.
Output Devices
Output unit displays the processed results. Examples are video terminals and graphic displays.
I/O devices do not alter the information content or the meaning of the data. Some devices can be used as output only e.g. graphic displays. Following are the Input / Output techniques
o Programmed Interrupt driven
o Direct Memory Access (DMA)
System Interconnection / BUS
“A bus is a communication pathway connecting two or more devices.” A key characteristic of a bus is that it is a shared transmission medium. Multiple devices connect to the bus, and a signal transmitted by any one device is available for reception by all other devices attached to the bus. If two devices transmit during the same time period, their signals will overlap and
become garbled. Thus, only one device at a time can successfully transmit. The communication between the external environment and CPU is established through the System Bus. System bus is classified into three different types, depending on whether it carries Data, Control, or Address
information