BASIC COURSE OF COMPUTERTutorial 1 Introduction To Computer System Organisation

Some Key TerminologyComputer A Computer is an electronic device that can perform a variety of operations in accordance with a set of instructions called program.Data Data in Computer terminology means raw facts and figure.Information It means what we get after processing data(meaningful data).

Input, Process and OutputIPO Cycle

The computer take Input from the input devices attached to it.After taking Input from the input devices the system process data with the help of CPU (Central Processing Unit).The output unit is formed by the output devices attached to the computer.

The MemoryThe memory of Computer is often called main memory or primary memory. It is generally the third component of CPU.A memory cell can be defined as a device which can store a symbol selected from a set of symbols.

Bit, Bytes and NibbleThe smallest individual parts of the Memory is known as bits. A bits means a binary digit i.e. either 0 or 1. A number of bits together are used to store data instructions by their combination.A bit is the elementary unit of the memory.A group of 8 bits is called a byte.A group of 4 bits is called a nibble.One byte is the smallest unit which can represent a data item or a character. Other units of memory are KB,MB,GB and TB.

Relationship between different units of Memory1 KB(kilobytes) means 210 bytes i.e. 1024 bytes.1 MB(Megabytes) means 210 KB i.e. 1024 X 1024 bytes1 GB(Gigabytes) means 210 MB i.e. 1024X1024X1024 bytes.1 TB(Terabytes) means 210 GB i.e. 1024X1024X1024X1024 bytes.

Hardware and SoftwareHardware represents the physical and tangible components of the computer i.e. components that can be seen and touched.Input devices, CPU, Floppy Disk, Pen Drive, Hard Disk are example of computer hardware.Software represents the set of program that govern the operation of a computer system and make the hardware run.

Categories of SoftwareSoftware can be classified broadly into three categories:-Operating SystemLanguage ProcessorApplication Software Out of these three the first two are in the category of System Software.

Operating System(OS)An Operating System is a program which acts as an interface between a user and the hardware(i.e. all computer resources).An Operating system is an important components of computer system which controls all other components of the computer system.Major components of Computer system are:-The HardwareThe OSThe Application ProgramsThe Human ware(Users).

Main Functions of OSIt provide the instructions to prepare user-interface i.e. way to interact with user whether through typed commands or through graphical symbols.Loads necessary programs(into the computer memory) which are required for proper computer functioning.Coordinates how programs work with the CPU, Keyboard, Mouse, printer and other hardware as well as with other software.Manages the way information is stored on and retrieved from disks.

Language ProcessorsA programmer prefers to write their programs in one of the high Level language(HLLs) because it is much easier to code in such language. However, the Computer does not understand any language other than its own machine language(binary language) therefore, it becomes necessary to process a HLL program so as to make it understandable to the computer. The System programs which performs this job are known as language processors.

Assembler, Interpreter and CompilerAssembler :-This Language processor converts the program written in assembly language into machine language.Interpreter:- This Language processor converts the program written in High level language in machine language by converting and executing it line by line. If there is any error in any line, it reports it at the same time and program execution cannot resume until the error is rectified.Compiler:- Compiler also converts the HLL program into Machine language but the conversion manner is different. It converts the entire HLL program in one go, and reports all the errors of the program along with the line numbers.

Application SoftwareAn Application Software is the set of programs necessary to carry out operations for a specified applications.These are the programs written by programmers to enable computer to perform a specific task such as inventory control, medical accounting, financial accounting, result operations, billing etc.

Categories of Application SoftwareCustomised Application Software:- This type of software is tailor-made software according to a users requirements. The software is developed to meet all the requirements specified by the user.General Application Software:- This Type of software is developed keeping in mind the general requirements for carrying out a specific task. Many users can use it simultaneously as it fulfills the general requirements.

Strengths and Weaknesses of a ComputerSpeedHigh Storage CapacityAccuracyReliabilityVersatilityLack of decision Making PowerIQ Zero

Firmware and LivewareLike Hardware and Software, Firmware is another term which is commonly used. Firmware is prewritten program that is permanently stored in read-only memory. It configures the computer and is not easily modifiable by the user. BIOS instructions are an example of Firmware.Liveware is the term generally used for the people associated with and benefited from the computer system.

The Generation of ComputerThe First Generation Computers(1949-55)The Second Generation Computers(1956-65)The Third Generation Computers(1966-1975)The Fourth Generation Computers(1976-Presents)The Fifth Generation Computers(Coming Generation)

The First Generation of ComputersSome Key Features of First Generation are as follows:-Used Vacuum tubes.Big and clumsy computers.Electricity Consumption High.Programming in Machine Language.

The Second Generation of ComputersSome Key Features of Second Generation are as follows:-Transistor replaced vacuum tubes.Computers became smaller.Generate less heat.Electricity consumption lower.More reliable.

The Third Generation of ComputersSome Key Features of Third Generation are as follows:-I.C. Developed.Computers faster, smaller and more reliable.Power consumption lower.High-level languages appeared.

The Fourth Generation of ComputersSome Key Features of Fourth Generation are as follows:-Portable Computer developed.Micro Computers series such as IBM and APPLE developed.Great development in data communication.Different types of secondary memory with high storage capacity and fast access developed.

The Fifth Generation of ComputersSome Key Features of Fifth Generation are as follows:-Parallel Processing.A.I.Superconductors.Robotics Machines.

Input, Output and Memory DevicesThere are variety of input units which are used by computers. They are categories under two section:-(a) General Purpose Input device.(b) Special purpose Input device.Keyboard is the example of general purpose input device.

Special Purpose Input DeviceMICR(Magnetic Ink Character Reader).OCR(Optical Character Reader).OMR(Optical Mark Reader).Mouse.Scanner.Light Pen.Microphone.Joystick.Biometric Sensors.Bar Code Reader. Smart Card Reader.Digital Camera. Touch Screen.

Difference between OCR and OMRAn OCR is used to read characters of special type font that are printed on conventional paper with conventional link.An OMR is used to transcribe mark that are marked with a dark pencil or ink on a special preprinted form.

Output DevicesVDU(Visual Display Unit).LCD(Liquid Crystal Display).Speakers.Plotters.Printers.

Types of PrinterThey are of two types:-Impact Printer:- In these printer there is mechanical contact between the print head and paper.Non-Impact Printer:- In these printer, there is no mechanical contact between the print head and paper.

Types of Impact PrinterThe Impact printer can further be classified into following categories:-(i) Line Printers(ii) Character Printers(Serial Printers). There are two types of Line printer which are drum printer and chain printer. Line printers are designed for heavy printing applications and can print continuously for a few hours.

Character Printers(Serial Printer)They are divided into two categories:-DMP (Dot Matrix Printer).Letter Quality Printers. In DMPs, the printing head contains a vertical array of pins. As the head moves across the paper, selected pins fires against a linked ribbon to form a pattern of dots on the paper.

Non Impact Printers ExamplesElectromagnetic Printers.Thermal Printers.Electrostatic Printers.Inkjet Printers.Laser Printers. Out of these the last two categories are used frequently now a days.

Compacting Reduces Database Storage Size

MEMORY DEVICESIts an essential component of every computer.Memory can be broadly classified into twoMain Memory/Primary Memory Internal memory of a computer system.Secondary Memory External memory that can be attached to the computer system.

The Main MemoryThe Main memory is divided into two partsRAM (Random Access Memory) In RAM, any cell can be accessed from any desired random location. Information can be read from and write into in RAM. ROM (Read Only Memory) In ROM, information can only be read from. No write operation can take place in ROM.

Random Access Memory(RAM)RAM is a volatile memory. That is, when the power goes off, the contents of RAM get erased.Ram can be classified into two categories-Dynamic RAM Consist of transistor and capacitor thats capable of storing an electric charge. The capacitor either contains no charge(0 bit) or does hold a charge.(1 bit)

Static RAM It consist eventually of internal flip-flops( a binary cell capable of storing one bit of information) that stores a binary information. Static RAMs take up more space for a given storage capacity than do dynamic RAMs.

Read Only Memory(ROM)This memory performs the read operation only, it does not have a write capability. ROM is non volatile, i.e. ROM is made permanent during the hardware production of the unit and can not be altered by writing different words into it.There are various types of ROM which are given below-

PROMPROM stands for Programmable Read Only Memory, that can be programmed to record information using a person known as PROM programmer. Once the chip has been programmed, the recorded information can not be changed i.e. PROM becomes same as ROM.

EPROMEPROM stands for Erasable Programmable Read Only Memory.It is another type of ROM that can be erased and the chip can be programmed to record different information. Erasing is achieved by exposing the chip to ultraviolet light.

EEPROMEEPROM stands for Electrically Erasable PROM. This type of ROM can be programmed and erased by electrical signals. It does not require exposure to ultraviolet light to erase its content. One of its new application is a Back-up to RAM memory whose contents are lost in a power failure.

CACHE MEMORYIt is a special high-speed storage mechanism. It can be either a reserved section of main memory or an independent high-speed storage device. Whenever some data is required, the CPU first looks in the cache, if it is there or not. If the data is found there, CPU does not access main memory and hence the process becomes very fast.

Secondary Memory DevicesAs Primary memory has a limited storage capacity and is not permanent, secondary storage devices are used to store large amount of data permanently. Various secondary devices available are-Magnetic DiskHard Disk

The Magnetic DiskThe magnetic disk storage provides large storage capability with moderate operating speeds.Magnetic disks stores information on one or more circular platters or disks.A disk pack generally contains 6 platters, each platters having two surface, i.e. its two sides.

The Magnetic disk Continued..The disks are continuously spinning.These rotating disks are coated with a magnetic material.Information is recorded on the surface of rotating disk by magnetic heads.Information is stored on the bands formed by the head(s).Each band of information on a disk is a circle, called a track.

Magnetic disk Continued.All tracks are concentric circles. Bits are recorded along a track in fixed length physical blocks called sectors.The Magnetic disk example is Hard disk.

Types of Magnetic DisksThe Hard Disk- The hard disk memories or store information on one or more circular platters(or disks)which are continually spinning.Concentric circles on the magnetized surface of the magnetic disks are known as tracks.The tracks on the disk surface are divided into invisible segments known as sectors.Similar numbered tracks on different platters of a hard disk form a Cylinder.

Optical DisksWith the advent of technology, the need and requirement of high-storage devices is on the rise.The optical disks compared to magnetic disks can provide higher recording densities.The optical storage techniques make use of laser-beams for recording information.

Types of Optical DisksThe Compact Disk(CD).Digital Video Disk or Digital Versatile Disk (DVD) DVD come in two formats:-DVD video FormatDVD-Rom

DVD Video FormatThe DVD video format is used for home movie entertainment through a DVD player.

DVD players are backward compatible to existing technologies, so they can play Audio CD and CD-ROM format.

DVD-ROMThe DVD-ROM stores computer data.

DVD-ROM uses include interactive games , Video file storage and photographic storage.

Computer SecurityIt is the ability of a system to protect information and system resources with respect to confidentiality and integrity.

Basic Components of Computer SecurityComputer security is frequently associated with three core areas, Which can be conveniently summarized by the acronym CIA.ConfidentialityIntegrityAuthentication

Threats to Computer SecurityA threat is a potential violation of security. When a threat is actually executed, it becomes attack.

The persons who execute such actions or cause them to be executed are called attackers.

Common types of ThreatsSome common threats are given below:-VirusesWormsTrojansSpywareAdwareSpammingPhishing

Computer VirusesComputer viruses are malicious codes/programs that cause damage to data and files on a system. Two other similar programs also cause virus like effects. These are:-Worms A worm is a self-replicating program which eats up the entire disk space or memory. A worm keeps on creating its copies until all the disk space or memory is filled.

Trojan HorsesA Trojan horses is a program that appears harmless(such as text editor or a utility program) but actually performs malicious functions such as deleting or damaging files.

SpywareIt is a software which is installed on your computer to spy on your activities and report this data to people willing to pay for it. It track the user behavior and reports information back to a central source.

AdwareThese are the programs that deliver unwanted ads to your computer(Generally in the pop-up forms). They consume your network bandwidth and hence slow the browsing speed.

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