FUNDAMENTAL OF COMPUTER STUDIES PART-3
TYPES OF
COMPUTERS
Analog computer
These systems
were the first type to be produced. It is an electronic machine capable of
performing arithmetic functions on numbers which are represented by some
physical quantities such as temperature, pressure, voltage, etc. Analog refers
to circuits or numerical values that have a continuous range. Popular analog computer
used in the 20th century was the slide rule.
Digital
Computers
Virtually all
modern computers are digital. Digital refers to the processes in computers that
manipulate binary numbers (0s or 1s), which represent switches that are turned
on or off by electrical current. A bit can have the value 0 or the value 1, but
nothing in between 0 and 1. A desk lamp can serve as an example of the difference
between analog and digital. If the lamp has a simple on/off switch, then the
lamp system is digital, because the lamp either produces light at a given
moment or it does not. If a dimmer replaces the on/off switch, then the lamp is
digital, because the amount of light can vary continuously from on to off and
all intensities in between. Digital computers are more common in use and it
will be our focus of discussion.
Hybrid Computer
This is when a
computer make is of both analog and digital components and techniques. Such computer
require analog to digital and digital to analog converter which will make
analog and digital data palatable to it. The basic classification nowadays uses
the following.
1. The Desktop
A computer is
referred to as "desktop" when it is relatively small enough to be
positioned on top
of a table where
a person is working. Such a computer can also be placed on the floor or somewhere
under, or aside of, the table, in which case the monitor would be placed on top
of the table. This is the most common type of computers used in the office or
at home. A desktop computer is made of different parts that are connected with
cables.
2. The Laptop
A computer is
called laptop when it combines the CPU, the monitor, the keyboard, and the
mouse in one unit to be so small that you can carry it on your laps when
traveling or commuting. A laptop is also called a notebook. Other parts, such
as an external mouse, an external keyboard, or peripherals such as a printer or
a projector, can be connected to the laptop. A laptop is only physically
smaller than a desktop but, everything considered, it can do anything that a
desktop can do.
3. The Server
A server is a
computer that holds information that other computers, called workstations, can
retrieve. Such workstations are connected to the server using various means.
This means that they could be connected using cable, wireless connection, etc.
Only computers that maintain a type of connection with the server can get the
information that is stored in the server.
Normally,
although not particularly recommended, any computer, including a desktop or
even a laptop can be used as a server, as long as it can do the job required. A
server is more defined by the program (called an
operating system) that is
installed in it, not how the machine looks.
Any type of computer, including a
desktop, a laptop, a CD or DVD machine, etc can be connected to a server.
The person who sets up a server
also defines the types of connections it is made for.
4. The Mainframe
A mainframe is a computer,
usually physically big, that does almost all the jobs for other types of computers
that are connected to it. This is a broad definition but other aspects are
involved. Like a server, the program (operating system) that runs in the
mainframe defines its role.
ANATOMY OF COMPUTER SYSTEM
A typical computer system irrespective of its size, class or type consists of hardware and software,
integrated and harmonized together to perform computational work (scientific or military) or data processing.
COMPUTER HARDWARE
Hardware system: Computer hardware consists of the components that can be physically handled. It
refers to the physical units or machine of functional units, which makes up the computer configuration which is done to suit the goals and objectives of the user. The function of these components is typically divided into three main categories: input, output, and storage. Components in these categories connect to microprocessors, specifically, the computer’s central processing unit (CPU), the electronic circuitry that provides the computational ability and control of the computer, via wires or circuitry called a bus. Hardware may be classified into Central Processing Units (CPU) and the peripherals. The CPU entails Control Unit (CU), Arithmetic and Logic Unit (ALU) and the Internal Memory Unit (IMU) or main memory. The peripherals consist of the input, output and Auxiliary Storage Units.
Strictly speaking, computer is made up of five district elements to include:
1. A central processing unit (ALU and CU)
2. Input unit
3. Output unit
4. Storage unit (Internal and Auxiliary)
5. The communication network; “Bus” that links all the elements of the system, and connects the
6. External world. (Cables and Cords)
MOTHERBOARD: The motherboard is a printed circuit board that connects other components through the use of traces, or electrical pathways. The motherboard is indispensable to the computer and provides the main computing capability. Personal computers normally have one central processing unit (CPU) on the motherboard.
THE CENTRAL PROCESSING UNIT (CPU)
This is the main brain of the computer that accepts data, performs operations on the data and sends out the result.Information from an input device or from the computer’s memory is communicated via the bus to the Central Processing Unit (CPU), which is the part of the computer that translates commands and runs programs. It consists of ALU and CU, and a single chip or series of chips that performs arithmetic and logical calculations and controls the operations of the other elements of the system.
Most CPU chips are composed of four functional sections:
1. ALU: Calculating ability either arithmetical or logical operations.
2. Registers: Temporary storage areas that hold data, keep tracks of instruction, and hold the location and results of these operations.
3. Control section: Times and regulates the operation of the entire computer system, by using its instruction decoder to read patterns of data in a designated register and translate the patterns into activities, such as addition or comparison. It also uses its interrupt input to indicate the order in which individual operations uses the CPU and regulates the amount of CPU time allotted to each operation.
4. Internal Bus: Network of communication lines that connects the internal elements of the processor and also leads to external connectors that links the processor to the other element of the computer.
The main functions of the microprocessor (CPU clips) includes the following.
a. Control use of the main storage in storing data and instructions (i.e the ROM).
b. Control the sequence of operations.
c. Give commands to all parts of the computer system.
d. Carry out processing.
INPUT DEVICES
Input unit consists of external devices—that is, components outside the computer’s CPU. It provides or fetches information and instructions to the computer. These include keyboard, mouse (mechanical/ optomechanical/ opticals), light pen, joystick, scanner, microphones (voice recognition modules), Optical Character Reader (OCR), Magnetic Ink Character Reader Recognition (MICR), bar code reader, badge reader, digitizer, touch screen and optical mark reader (OMR).
A. Light pen: This is a stylus with a light sensitive tip that is used to draw directly on a computer’s video screen or to select information on the screen by pressing a clip in the light pen or by pressing the light pen against the surface of the screen. The pen contains light sensors that identify which portion of the screen it is passed over. It is mostly used with Laptop.
B. Mouse: This is a pointing device designed to be gripped by one hand. It has a detection device (usually a ball) on the bottom that enables the user to control the motion of an on-screen pointer, or cursor, by moving the mouse on a flat surface. As the device moves across the surface, the cursor moves across the screen. To select items or choose commands on the screen, the user presses a button on the mouse.
C. Joystick is a pointing device composed of a lever that moves in multiple directions to navigate a cursor or other graphical object on a computer screen.
D. Keyboard: Keyboard is typewriter-like devices that allows the user to type in text, numeric and execute commands with the aid of the functional keys on the keyboard.
E. Optical Scanner: This is light-sensing equipment that converts images such as a picture or text into electronic signals that can be manipulated by a computer. For example, a photograph can be scanned into a computer and then included in a text document created on that computer. The two most common scanner types are the flatbed scanner, which is similar to an office photocopier, and the handheld scanner, which is passed manually across the image to be processed.
F. Microphone: This is a device for converting sound into signals that can then be stored, manipulated, and played back by the computer. A voice recognition module is a device that converts spoken words into information that the computer can recognize and process.
G. Modem: It stands for modulator-demodulator, is a device that connects a computer to a telephone line or cable television network and allows information to be transmitted to or received from another
computer. Each computer that sends or receives information must be connected to a modem.
