COMPUTER SYSTEM ORGANISATION-SHORT NOTES-WITH HELPFUL DIAGRAMS - CLASS 11-CBSE

        COMPUTER ORGANIZATION     refers to the logical structure of a computer describing how its components are connected to one another, how the effect one another function is and contribute to overall performance of the computer.

• Computer follows input- process -output principle (IPO principle).
• An input unit takes the input and converts it into binary form so that it can be understood by computer.
• Some common input devices are keyboard, mouse, microphone etc.
• A computer can understand two stages on/ off or high/low voltage of the binary language that uses just two symbol 1 for on and 0 for.
• Output unit convert the output in binary form to human readable form.
• Some popular output devices are monitor, printer, speaker,etc.
• The CPU or the central Processing Unit is the main control centre and Processing Unit . 
• It is also called brain of the computer as it guides direct control over the performance of a computer . 
• CPU has some sub -components that help in carrying out the processing of a task . These are arithmatic logic unit, control unit and registers.
• ALU performs all arithmetic and some logical operations. when two numbers are required to be added, this number send  from memory to ALU whete addition  take place and the result is put back in the memory.
• The CU controls and guides the interpretation flow and manipulation of all data and information.
• Registers or processor register are small units of data holding places . The CPU uses register to temporary hold some important for the thing information during that time the processing is taking place.
• CU the supervisor by controlling and guiding the operation taking place.
• The memory of a computer is more like a predefined working place where it temporarily keeps information and data to facilitate its performance.
• The memory of a computer is often called main memory or primary memory.
• A group of 8 bit is called a byte and a group of 4 bits is called a nibble. 
• 1 byte is a Smallest unit which can represent a data item or a character other units of memory are KB ,MB ,GB ,TB,etc.

BASIC COMPUTER ORGANISATION 

       

• The components of a computer system make the physical structure of a computer.

        A computer system comprises of five basic components-

1.  INPUT UNIT-  It is responsible for taking input for the computer the . Input devices attached to the computer system make the input unit.
2. OUTPUT UNIT - It is responsible for take giving input for the computer . Output devices attached to the computer system make the output unit.
3. CPU (Central Processing Unit ) - It is responsible for processing the data and instructions . It comprises of the following part - Arithmetic and logic unit, control unit and register.
4. PRIMARY MEMORY- It is the internal volatile memory where data and instructions are stored during processing.
5. SECONDARY STORAGE UNITS-It refers to the external storage devices which provide permanent memory to the computer system.

RAM

•  It is also known as Random Access Memory.
• It is a volatile memory that is when the power goes off the contents of RAM get erased.
• In the Random Access Memory the memory cells can be accessed for information transfer from any desired random location.
• Ram chips in a computer can be of two basic type dynamic RAM and static RAM.
• DYNAMIC RAM-  These are made up of transistor and capacitor . 
• The amount of time of taken to produce data required from memory from the start of access until the availability of data is called memory access time. 
• STATIC RAM- These are made up of flip flops and other faster access time than DRAM.
• A flip-flop is a binary cell capable of storing one bit of information.

ROM

•   It is also known as read only memory.
• Read only memory is restricted to reading words that are permanently stored within the unit.
• It is a memory unit that performs the read operation only.
• It does not have a a writing capability.
• There are various types of read only memory -1. Programmable read only  memory.                                                          2. Erasable Programmable read-only memory.                                                          3. Electrically erasable Programmable Read Only Memory.                                        4. Flash electrically erasable Programmable read only memory.             5. Mask read only memory.

CACHE Memory

•  Pronounced as ' cash'. 
• It is a special high speed storage mechanism.
• It is a high speed memory available inside CPU in order to speed up access to data and instructions stored in a RAM memory.
• It can be either reserved section of main memory or an independent high-speed storage device or even on CPU chip.

STORAGE DEVICES

•  Since the computer's main memory is temporary, secondary memory space is needed to store data and information permanently for later use. The most common secondary storage media are hard disk, CD RW, pendrive etc. The secondary memory devices are known as storage devices. 

STORAGE UNIT

•  The most common storage devices are  hard disk, CD ROM ,DVDs pendrives.
• Hard Disk memory store information on one or more circular this which are continually spinning. This rotating disc are coated with magnetic material and stacked with space between them . Information is recorded on the surface of a rotating disc by magnetic heads as tiny magnetic spots. 
• The compact disk are  optical media and  are relatively cheap and have  storage capacity up to 700 MB. There are three main types of CDs-                                        1. Compact disc read only memory which is used only to store information and cannot be used to store data.                2. Compact disc recordable is mainly used for CD-R and can re- written for  only once and disk can't be erased.                       3. Compact disc rewritable is an Irreversible disc and we can write on multiple times.
• DVD is an optical storage device that looked the same as compact disk but is able to hold about fifteen times as much information and transfer it to the computer about 20 times as fast as CD ROM. A DVD is  called as super density disc(SD). It can hold up to 17 GB of data or 4 hours of movie on a side.  DVDs also come in three varieties-  DVD ROM,  DVD recordable , DVD rewritable.
• Flash drive is a small Ultra portable storage device with the solid state memory that is it has no moving parts and like Magnetic storage devices not does it make use of laser unlike optical drives in speed it work in a similar way to RAM. It has a typical size range from 256 MB up to 128 GB and beyond.
• Blu-ray disc ,also known as BD , is an optical disk storage media format . Its main uses is high  definition video and data storage.

SYSTEM BUS

•   System bus is an electronic pathway composed of connecting cable and that connects the major components of a computer system .
• Through system bus data and instructions are passed among the computer system components.
• The data carrying part of system bus is called data bus.
• The control instruction carrying part of system bus is called control bus.
• The memory address carrying part of system bus is called address bus.
• A separate type of bus called I/O bus connects the input-output and other external devices to the system.

MOBILE SYSTEM ORGANISATION 

•   Mobile processor-  This is the brain of a smartphone and  is also called mobile CPU. It receives  command ,make instant calculations, play audio/video , store information and place signal throughout the device. It has two sub-processor-           1. Communication Processing Unit (responsible for making and receiving phone calls)                                                     2. Application Processing Unit(responsible for governing controlling all types of operations taking place on a mobile system by running various types of mobile applications).
•  Display subsystem is responsible for providing display facilities ,touch sensitive interface and touch sensitive keyboard.
•  Camera Subsystem is designed to deliver a tightly bound image processing package and enable and improve overall picture and video experience.
• Mobile system memory is comprised of following two types of memories Random Access Memory(RAM), Read only memory(ROM).
• Storage It is also called expandable storage and comes in form of SD cards or micro SD card . It is the storage which can be removed easily by Earth and can be used for storing pictures,  music ,videos and links.
• Power management system (battery) is responsible for providing power to a mobile system . The mobile systems work on a limited power to provided  through an attached  unit . This subsystem has a battery management system that works with a battery charger and battery unit and provides power to the mobile system in required form.

TYPES OF SOFTWARE

    A computer system consists of hardware and software for its proper functioning.

Hardware represent the physical and tangible components of the computer that is component that can be seen and touched .

Software represent the set of programs that govern the operation of a computer system and make the hardware run.

          It can be further classified into two type 

1. System software 

2.Application software

1. System software.                                       It control internal computer operations. It can be further classified into two categories -                                                                             A.  Operating system( it is a program which acts as an interface between user and hardware. There are different types of operating system available today . Some of them are single user OS ,multi user OS ,time sharing OS, real time OS ,multiprocessing OS)                                  B. Language processor ( It is a special type of computer software that can translate the source code into an object code or machine code . There are three types of language processor ASSEMBLER, convert the program written in assembly language into machine language; COMPILER , it is another type of system software that translate and executes instructions written in a computer program in one go; and INTERPRETER , it is a type of system software that translate and executes instructions written in computer program line by line ,unit by unit,etc).
2. Application Software  - It is the set of programs necessary to carry out operations for a specified application.             It can further be subdivided into 4 categories.                                                      1.  Packages utilities, design for individual using purpose in manner it suit their needs and requirements . Some major and most common categories of packages are word processing software, spreadsheets ,database management system ,desktop publishing software etc;             2.  Customised software.                             3.  Developer tool.                                         4. Utilities are those  application programs that assisst the computer by performing housekeeping functions like backing up disk /scanning cleaning viruses or arranging information etc.  Some of important utilities are -text editor, backup utility ,compression utility, disk defragmenter and  antivirus software.

Working hierarchy in a computer 

BUSINESS SOFTWARE-  This type of software is specifically created according to business requirement . This type of software is developed to meet general requirements of a business . Some of most famous business software are INVENTORY MANAGEMENT SYSTEM ( for managing inventory details of a company), PAYROLL SYSTEM( for handling payroll of a company's employees )FINANCIAL ACCOUNTING,  HOTEL MANAGEMENT AND RESERVATION SYSTEM, etc.  

SOFTWARE LIBRARIES -   A software library is a  predefined and available to use suite  of data and programming code in the form of Pre written codes/ function/ scripts /classes etc that can be used in development of new software programs and applications.

For example ,Python come equipped with many software library . Some of these are -

                   Numerical Python

                   Scientific Python 

                   Panda library.