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Main » 2013 » August » 11 » COMPUTER HARDWARE
9:10 PM COMPUTER HARDWARE |
HARDWARE
Hardware is the various physical components that comprise a computer system, as opposed to
the non-tangible software elements. Most of these physical components are physically separated
from the peripheral to the main circuitry that does the arithmetical and logical processing but
they are the most familiar bits of a computer.
2.1 COMPUTER DEVICES
A computer consists of several interconnected devices or components. They are five basic
components, namely, central processing unit, primary storage, secondary storage, input devices,
and output devices. This physical equipment that make up a computer is called hardware.
Secondary storage, input and output devices are often called peripheral equipment. The CPU and
primary storage contain electronic circuits that store and process data or program instruction. The
circuits are formed from place of silicon which is non-metal element. A piece of silicon
containing electronic circuits is called an integrated circuit or a chip. The computer chips for the
CPU is called processor chips. In microcomputer, the entire CPU contains only one-processor
chips and is called microprocessor. In mini computer, mainframe computer or super computer,
the CPU may require several processor chips.
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Primary storage is composed of many chips for example; a microcomputer may have more than
sixteen chips. Each chip is called memory chip and is capable of storing a certain amount of data.
The amount of data depends on different types of chips. All the memory chips are made up
primary storage (RAM). In microcomputers, the microprocessor and the memory chips are
mounted on one board, called the Motherboard or mainboard. The chips in the CPU and primary
storage are connected by a set of wires called a bus. Data is sent back and forth between
components over the bus.
There are some other chips that are needed to control input/output devices and secondary
storage. Some of these chips are built-in Mainboard or are in a separate board. They are called
add-on-boards or cards, and are plugged into sockets on the mainboard. These sockets which are
called expansion slots are connected to the other components by the bus. The combination of all
these chips on or outside motherboard form computer devices. They are enclosed in a computer
casing. Other devices such as output devices (Monitor, Printer), Input device (keyboard, Mouse),
speakers are plugged into computer devices to form personal computer system.
Note in Microcomputer or stand-alone computer CPU may be regarded as microprocessor.
Primary storage may be regarded as Random Access Memory. Secondary Storage may be
regarded as Hard disk, Floppy disk or Compact disk.
2.2 CPU – CENTRAL PROCESSING UNIT
The Central Processing Unit s also called Processor. This is the brain or heart of the computer
equipment. The CPU carries out the calculations for the program and controls the other
components of the system. It does the function by organising circuits into two main units, called
Arithmetic logic unit and control unit.
The ALU contains circuits that do arithmetic and perform logical operations. The control unit
contains circuits that analysed and execute instructions.
The Arithmetic Logic Unit
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The ALU contains arithmetic circuits that can subtract multiply and divide two numbers. More
complex operations such as finding the square root of a number are done by sequence of their
basic operations. The ALU has logic circuits that can compare two numbers to determine if they
are equal or if one number is greater than storage locations called storage registers for storing
numbers used in calculations and for storing the results of calculations. To perform a calculation
or logical operation, number is transferred from primary storage to storage registers in the ALU.
These numbers are sent to the appropriate arithmetic or logic circuit. The results are sent back to
the storage registers. The results are transferred from the storage registers to primary storage.
The Control Unit
The control Unit controls the whole computer system by performing the following functions:
- directs and coordinates all operation called for by the program
- activates the appropriate circuits necessary for inputs and output devices.
- Causes the entire computer system to operate in an automatic manner.
The control unit contains a temporary storage location called an instruction register for storing
the instruction being executed. It also contains circuits called the instruction decoder – which
analyse the instruction register and cause it to be executed. The control unit executes each
instruction by following the same basic sequence of steps:
- the next instruction in the program is retrieved for primary storage and stored in the
instruction register
- the instruction is sent to the instruction decoder where it is analysed.
- The decoder sends signals to the ALU, primary storage, I/O devices, and secondary storage,
that cause the actions required by the instructions to be performed.
These steps are repeated for each instruction in the program until all instructions have been
executed.
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