Introduction to Computers: Hardware, Software, and Storage, Lecture notes of Information and Communications Technology (ICT)

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INTRODUCTION

TO

COMPUTERS

Introduction

A computer is an electronic device that works under control of instructions (programs) which is stored in its own memory. It can accept and store data, perform arithmetic & logic operations on the data and give out the processed data through the output devices.

A computer is an integral part of information system. An information System is a system that accepts Input (data), perform operations on these input (processes) and produce the output (information).

An information system may also be termed as a computer system and is a combination of the following five elements:

 hardware  software  Data/Information.  procedures  people

A computer is made of several units to form a system. These parts are as follows;-

1. The System Unit which house the CPU.
2. Monitor/screen/VDU.

 Keyboard and mouse.

Peripheral devices are those hardware devices that are connected to the computer, but your computer can function without them, since they are not part of the computer. These devices are:-

1. printer
2. scanners
3. CD/DVD ROM s
4. Floppy drive etc.

4. CMOS RAM – Complementary Metal Oxide Semiconductor Random

Access Memory

Motherboards also include a small separate block of memory made from CMOS RAM chips which is kept alive by a battery (known as a CMOS battery) even when the PC’s power is off. This prevents reconfiguration when the PC is powered on CMOS devices require very little power to operate.

The CMOS RAM is used to store basic Information about the PC’s configuration for instance:-

 Floppy disk and hard disk drive types  Information about CPU  RAM size  Date and time  Serial and parallel port information  Plug and Play information(PnP)  Power Saving settings

The Other Important data kept in CMOS memory is the time and date , which is updated by a Real Time Clock (RTC). It is sustained by CMOS batteries as shown below.

5. IDE /SATA Cables

Integrated Drive Electronics {IDE} and S erial A dvance T echnology A ttachment {SATA} are computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives and optical drives. SATA has several advantages over the older interface – IDE for the following reasons:

 It reduced cable size and cost (seven conductors instead of 40).  Native hot swapping i.e. operate when computer is on.  Faster data transfer through higher signaling rates, and more efficient transfer through an (optional) I/O queuing protocol.

Computer terminologies.

1. HARDWARE

Is a term used to describe all the physical components that make up a computer system?

2. INSTRUCTIONS

These are commands issued to computer to perform certain operation and the computer will accept these instructions and perform them. These instructions are also referred to as programs (software)

3. SOFTWARE

It refers to various programs that are run by the computer. These are set of instruction written in the language of the computer and used to make the computer perform a specific task.

There are two types of software namely;-

1. System software-Computers’ programs
2. Application software-Users’ programs

System Software.

These are programs which were designed to provide an interface between the computer and the user to run other programs known as application software. They were designed to:-

1. Manage and control the computer hardware operations.
2. To load in application software in a computer.
3. To manage the computer data files.
4. Report the status of the computer.
5. Shows the memory capacity and usage.
6. Shows various files in the storage etc.

Example of system software include, operating systems {Windows, Linux, Mac MS-DOS etc.}, and the Utility software like Anti-virus programs.

Application Software :

This is a collection of related programs that are used to perform various jobs/tasks. They are programs written to solve specific problems like:-

What happens when you switch on the

computer?

The process of starting a computer is called booting. The computer first checks its memory (ROM) and some other components. After that, the drive begins to spin and the boot process will commence.

The system then reads drive C for the operating system. If it does not find it, in drive C, it checks others drives. On finding the OS, it reads COMMAND.COM. This is the command processor file. It contains all internal commands e.g. CLS, DATE, TIME etc.

After reading the command.com, it checks if autoexec.bat exists. If it does, it carries on the commands in that file. If it does not exist, it prompts for date, time after which the prompt appears.

Qualities of a computer.

1. A data processor: process raw facts and figures to produce information.
2. It is storage: stores information for later reference
3. It is automatic- can work with minimum human intervention once supplied with instruction and data.
4. It is electrical: it requires some sort of power to drive.

ADVANTAGES.

 Stores large chunks of information in a limited space.  Speed: performs tasks in a very short period.  Efficiency: creates an all-round saving on space and time.  Consistency: gives the same results given the same data and instruction (GIGO).  Secrecy: information is fairly protected if the computer system is well managed.  Versatility: can do the same thing over and over without getting worn out.  Flexibility: can perform a variety of jobs as long as there is a well-defined procedure.

DISADVANTAGES.

 Computer costs are expensive and maintenance is also high.  Reduce employment opportunity.  Needs expertise which is expensive to hire and maintain.  Loss of information if not well managed.  Social unrest- can cause of loss/redundancy.  Technology: due to change in technology, there is no guarantee that the already bought machine could become obsolete in a coup of months.

Classifications of Computers.

Computers can be classified using several criteria such as:

1. Size
2. Purpose
3. Type of Data they process and so on.
4. SIZE

There are four types of computers according to size. They are:-

Super Computers:

 They are the largest computers to be invented.  They are very expensive, very fast, and the most powerful computers in the world. They are quite rare as they are mainly used in scientific research stations i.e. nuclear stations and weather forecasting stations.

Mainframes:

 They are of medium size.  They are less expensive as compare to super computers.  Stores data on magnetic media.  They are used in places like insurance companies and airline reservations.

Mini-Computers:

 These are smaller and less powerful than mainframes.  They are multitasking i.e. several people can also use them from different locations at the same time.

Microcomputers (Personal Computers):

These are the smallest machines in the range of computers made to fit on desktop for an individual person’s use, while some are portable. They are the latest machines to be developed. An individual at work or home can use them.

They can be classified into two categories;

1. Desktop-Designed to be placed on the desk.
2. Laptops – Are Portable computers powered by rechargeable batteries and are smaller than desktop PCs. They range in size and can be called laptops, Notebooks and Sub- notebooks. Palmtops are the smallest PCs and are only about the size of a calculator.

Computer generation.

The first electronic computers were produced in the 1940s.Since then, radical changes in electronics have occurred. With each major breakthrough, the computers based upon the older form of electronics have been replaced with the new form of electronics thus forming the generation of computers.

1. First Generation-(1940s)

 These were earliest computers using vacuum tubes as their key electronic devices.  They had the biggest size.  They used punch-card as their input device.  They had an operation speed of 40,000 operation /sec  They produced a lot of heat, thus had a higher chance of breaking down.  They only required an expert to operate and were the most expensive.

2. Second Generation-(1950s).

 These were more reliable than the first generation.  The key electronic device was the transistor.  They were smaller in size than first generation.  Their speed was 200,000 operation /sec.  They were less expensive than the 1st  Their internal memory was in a form of magnetic tape.

3. Third Generation-(1960s-1970s)

 These were more powerful and reliable computers using simple integrated circuits.  Their size was smaller than the first and second generation.  Their processing speed was higher, 1,000,000 operation /sec  They were multitasking in nature.  They had a higher internal storage.

4. Fourth Generation.

 These are the computers in use today which contain more complex microelectronic devices.  They are the smallest in size.  They have higher processing speed.  They have a higher internal storage capacity.  They are very cheap as compared to the other.

5. Fifth Generation.

There are many predictions that by the end of this century, computers will be able to converse with people in human – like manner and which will be able to mimic human sense, manual and intelligence

Components of a computer.

It is made up of the following:

 Org ware/liveware/operator.

1. HARDWARE.

A computer can be thought of having four main elements as follows:

 The input devices.  The processing unit.  The storage unit.  The output devices.

A). INPUT DEVICES

Input devices are used to communicate with a computer. They offer an interface between the user and the computer. They also let users enter information and issue commands. Examples include:

(a) Keyboard

Enable operator/user to key in information into a computer. There are two types of keyboard:

1. Standard keyboard.
2. Enhanced keyboard.

The main difference between the two keyboards is:

1. The position of the function key pad.
2. The division of the numeric key pad.
3. The extra function keys.
4. The extra CTRL, ALT & SHIFT keys.

(g) Smart Card

This is a credit card with a built-in microprocessor and memory used for identification or financial transactions. More secure than plastic cards and can be programmed to self-destruct if the wrong password is entered too many times.

(h) Cash Dispensers (Automated Teller Machines – ATM)

Mainly used by banks. Customer or User is provided with a plastic embossed card with information encoded on a magnetic strip.

(i) Magnetic Ink Character Recognition (MICR)

This technology is mainly used by banks. Characters are printed in ink that can be magnetized so that after being subjected to a magnetic field, they can be read and decoded automatically. Read using a device called Magnetic Ink Character Reader (MICR).

Others include:

Microphones: – For voice recording and editing by the computer.

Optical Mark Readers : – Frequently used in forms, questionnaires and answer sheets.

Tracker Ball : – Used on modern portable computers, where there may be no space on which to use a mouse.

Touch Pad : – stationary pointing device used mainly on laptop computers. Provide a small, flat surface that you slide your finger over using the same movements as you would use a mouse.

Touch Screen : – an input device that allows user to interact with the computer by touching the display screen. Often this uses beams of infrared light that are projected across the screen surface.

Light Pen: – a light-sensitive stylus wired to a video terminal used to draw pictures or select menu options. Provide a very precise pointing capability directly on the screen

B). CPU.

This is where the main processing in the computer takes place. It’s the “brain” of the computer which regulates the operation of all system components and performs arithmetic and logic operation. The CPU has got 3 units namely:

o Control unit. o Arithmetic & logic unit. o Main memory.

(a) CONTROL UNIT.

The Control unit coordinates the various operations including receiving data, which enters the computer & deciding how and when the data should be processed. The control unit directs the operation of the arithmetic logic unit. It sends data to the ALU and tells it what functions to perform on the data and where to store the results. The ability of the control unit to accomplish these operations is provided by a set of instruction called an executive program which is stored in memory.

(b) ARITHMETIC UNIT.

The Arithmetic and logic unit performs operations such as addition, subtraction and comparisons. These operations are carried out on data in binary form. The logic section can also be used to alter the sequence in which certain conditions are indicated and to perform other functions, such as editing and masking data for arithmetic operations.

(c) MAIN MEMORY

It holds the current data and instructions. There are two types of memory:

Random Access Memory (RAM) for current data and Read Only Memory (ROM) for instructions.

There are several factors that determine the performance of a CPU.

 Processor Speed The processor gives you the speed you need to run applications, load images and download images. In other words, your processor is the brains of the computer. Remember, the higher the bandwidth and clock speed and the greater the number of cores you have, the higher the performance level of your computer.

 Memory(RAM) and your Operating System It is the RAM that allows you to work with more open program files without your system crashing. RAM is a temporary storage place of data that flows from your computer and processor. It is lost when you shut down your computer).

There are two kinds of storage in computers:

 Primary ( Main Storage)  Secondary ( Backing Storage)

Primary storage stores data temporarily while secondary storage stores data permanently. An example of primary storage is the Computer Memory and of secondary storage being the Hard disk, floppy disk, CD-ROM etc.

PRIMARY STORAGE – MAIN MEMORY.

(a) RAM

Random Access Memory is the place in a computer where the operating system, application programs, and data in current use are kept so that they can be quickly reached by the computer’s processor. When a computer shuts down properly, all data located in Random Access Memory is returned back to permanent storage on the hard drive or flash drive. At the next boot-up, RAM begins to fill with programs automatically loaded at startup, a process called booting

Note:

 RAM is a read/write memory i.e. the process of storing information in main memory is normally referred to as writing while the process of getting instructions is normally referred to as reading.  It is volatile memory. it retains information so long as power is on.  RAM is a temporal storage memory

N/B:

If RAM fills up, the processor needs to continually go to the hard disk to overlay old data in RAM with new, slowing down the computer’s operation. Unlike the hard disk which can become completely full of data so that it won’t accept any more. RAM never runs out of memory, but it keeps operating much more slowly than you may want it to.

Most personal computers are designed to allow you to add additional RAM modules up to a certain limit. Having more RAM in your computer reduces the number of times that the computer processor has to read data in from your hard disk, an operation that takes much longer than reading data from RAM. (RAM access time is in nanoseconds; hard disk access time is in milliseconds.)

Why Random Access?

RAM is called “random access” because any storage location can be accessed directly. Originally, the term distinguished regular core memory from offline memory, usually on magnetic tape in which an item of data could only be accessed by starting from the beginning of the tape and finding an address sequentially. Perhaps it should have been called “non-sequential

memory” because RAM access is hardly random. RAM is organized and controlled in a way that enables data to be stored and retrieved directly to specific locations. Note that other forms of storage such as the hard disk and CD-ROM are also accessed directly (or “randomly”) but the term random access is not applied to these forms of storage.

(b) ROM-Read Only Memory

ROM is “built-in” computer memory containing data that normally can only be read, not written to. Computer reads these instructions and cannot save any information in this type of memory. ROM contains the programming that allows your computer to be “booted up” or regenerated each time you turn it on. Unlike a computer’s random access memory (RAM), the data in ROM is not lost when the computer power is turned off. The ROM is sustained by a small long-life battery in your computer.

Note;

 ROM is permanent and cannot be changed i.e. it is non-volatile memory.  It is a Read Only Memory.  It is Non-volatile  ROMs are “ burnt in” at the manufacturing stage.

OTHER ROM

1. Programmable Read Only Memory (PROM)

It is a memory chip on which data can be written only once. Once a program has been written onto a PROM, it remains there forever. Unlike RAM, PROMs retain their contents when the computer is turned off. The difference between a PROM and a ROM ( r ead- o nly m emory) is that a PROM is manufactured as blank memory, whereas a ROM is programmed during the manufacturing process. To write data onto a PROM chip, you need a special device called a PROM programmer or PROM burner. The process of programming a PROM is sometimes called burning the PROM. Example of PROM include CD-R & DVD -R

2. Erasable Programmable Read Only Memory (E PROM)

This is a special type of PROM that can be erased by exposing it to ultraviolet light. Once it is erased, it can be reprogrammed. An EEPROM is similar to a PROM, but requires only electricity to be erased by exposure to Ultra-violet light. {CD-RW & DVD-RW}

it is called Local Disk C. If there are additional drives they are assigned the subsequent letters i.e. D, E etc.

The hard drive magnetically stores data on a stack of rotating disks called platters. A hard drive has read/write heads on each platter that read and record data on the disks. HDDs predominantly use SATA or IDE interface

Solid State Drive {SSD}

SSD can be thought of as an oversized and more sophisticated version of the humble USB memory stick. Like a memory stick, there are no moving parts to an SSD. Rather, information is stored in microchips.

An SSD does not have a mechanical arm to read and write data, it instead relies on an embedded processor (or “brain”) called a controller to perform a bunch of operations related to reading and writing data. The controller is a very important factor in determining the speed of the SSD. Decisions it makes related to how to store retrieve cache and clean up data can determine the overall speed of the drive.

Conversely, a hard disk drive uses a mechanical arm with a read/write head to move around and read information from the right location on a storage platter. This difference is what makes SSD so much faster.

As an analogy, what’s quicker? Having to walk across the room to retrieve a book to get information or simply magically having that book open in front of you when you need it? That’s how an HDD compares to an SSD; it simply requires more physical labor (HDD mechanical movement) to get information.

Floppy Disk

The most common types of floppy disks are 3 1/2 or 51/4 inch floppy disks. They are usually used to:

 Install new programs.  Transfer data.  Back up data.  Increase space in the hard drive

Note:

Back up is the process where a copy of a file, folder, or volume is stored on a separate storage device from the original, for the purpose of retrieval in case the original is accidentally erased, damaged, or destroyed.

CD-ROM Drive

Reads information stored on a Compact Disks (CD).CD-ROM stands for C ompact D isk R ead O nly Memory. CD-ROM (Compact Disc, read-only-memory) is an adaptation of the CD that is designed to store computer data in the form of text and graphics, as well as hi-fi stereo sound. Read only means that you cannot change the information stored on a disk.

A single CD-ROM disk can store more than 700 MB of data. This is equivalent to over 700 floppy diskettes.

Advantages of a CD

 The large storage capacity makes installing new programs on the computer easier.  It can store multimedia presentations.  You can play music on the drive while you work.  There are thousands of educational titles, games and encyclopedias on CD-ROM disks.

Handling a CD-ROM Disk

 When handling a CD-ROM disk, hold the disk around the edges.  Always place the disk back in its protective case.  Do not stack disks on top of each other.  Do not remove the disk or move the computer when the light on the CD-ROM drive in on.

Factors to consider when choosing a CD-ROM

Speed – It’s also called the data transfer rate. The speed of the CD-ROM determines how fast a disc spins. With faster speeds, a disk can transfer information to the computer more quickly, which results in better performance.

The available speeds are:

Single (1X) 150 Kb/s

Double (2X) 300 Kb/s

Triple (3X) 450 Kb/s

Quad (4X) 600 Kb/s

Six (6X) 900 Kb/s

Eight (8X) 1,200 Kb/s