CLASS -11 COMPUTER SCIENCE
CHAPTER- 12 COMPUTER SYSTEM OVERVIEW
🔔To download textbook pdf click on the ''DOWNLOAD'' button below -
NOTES FOR COMPLETE UNDERSTANDING -
- Computer is that factor which brought revolution in the world.
- “Computer is an electronic machine that accept input then do processing to produce output.“
- Computer is the combination of 2 main units - hardware and software .
- Hardware: Physical components are known as Hardwares. For eg. - Keyboard , Printer , CPU, Monitor, etc.
- Software: The sets of written programs which controls working of a computer system.
- Organization of Computer :
- Computer works as per Input-Process-Output Cycle (input ---> process ---> output).
- Computer processes a input and provides a required output.
- Computer system consists of various components like- CPU (ALU, Registers, Control Unit), Memory, input unit, output unit, Storage unit etc.
- Input Units --
- Input devices associated to a computer makes its input unit.
- Input unit is required to accept input and to convert it into computer comprehendible/understandable format.
- Some of the input devices are as under - • Keyboard • Mouse • Microphone • Joy-stick • OMR • OBCR • Touch Pad • Track Ball • MICR • Light Pen • Scanner • Camera • Bio metric Scanners • Touch Screen Panel
- Output Units –
- Output devices associated to a computer makes its output unit.
- It is the required to produce output after processing.
- Distinct output devices are used for specialised types of output.
- Some of the output devices are as under • Monitor • Projector • Printer • Plotter • Speaker
- CPU--
- Central Processing Unit is the chief controlling and processing unit of computer where all calculations takes place.
- It is also referred as brain of computer system as it directs, guides and controls working of computer system.
- CPU has following components : – Arithmatic logic unit (ALU) it performs mathematical and logical calculations. – Control unit (CU) controls and directs each and every task. – Registers it is the place to store data temporarily for the purpose of correct calculation.
- Memory --
- Memory is often known as Primary memory.
- Unlike human memory the data stored in this memory automatically flushes out with power cut off which can't be recovered later. It is also referred as volatile memory .
- It is a workplace in a computer system where data is stored on temporary basis for the purpose of processing any input or instruction .
- Every memory location has a definite address.
- Smallest unit of memory is a bit. – 8 bit = 1 byte – 4 bits=1 Nibble – 1024 byte = I Kilobyte – 1024 Kilobyte = 1 Mega byte – 1024 Megabyte = 1 Giga byte – 1024 Gigabyte = 1 Terra byte – 1024 Terra byte = 1 Peta byte – 1024 Petabyte = 1 Exabyte – 1024 Exabyte = 1 Zetta byte
- Time taken for accessing data from memory is called Memory Access Time.
- Types of Memory --
- Main Memory is divided into two types- – RAM (Random Access Memory) – ROM (Read Only Memory)
- The memory which is in direct association with CPU is known as primary memory. RAM and ROM both remains always in direct association with Central Processing Unit.
- RAM --
- In RAM, any memory cell can be accessed from any desired location of memory .
- The connection between memory and its environment is formed by data input, output lines, address lines, control lines which are used to direct transfer.
- Block diagram of RAM is as under-
- The only drawback of Random Access Memory is that it is volatile in nature.
- RAM is of two types- – Dynamic RAM (DRAM) – Static RAM (SRAM)
- It is impossible to imagine processing in absence of RAM.
- The capability of RAM depends upon the size (capacity) of RAM.
- RAM supports both read and write operations.
- DRAM :
- DRAM basically consists of transistors & capacitors that stores electric charge.
- As per switching of Transistor, capacitor does contain a unit of charge (1 bit ) or does not contain a unit of charge(0 bit).
- Now-a-days, memory access time of DRAM chip varies from 20 to 70 nanoseconds.
- Storage density of DRAM varies from 10 to 100 Giga bits.
- DRAM needs to be refreshed again and again which is a boring and time-consuming job for processor.
- SRAM :
- Static RAM is made of internal Flip-Flops and each Flip-Flop is capable of storing 1 bit.
- It needs more space as compared to DRAM.
- It is fast as compared to DRAM.
- SRAM is expensive as compared to DRAM.
- ROM :
- As its name signifies, this memory is meant for read operations.
- It is programmed at the time of hardware setting & whatever we store in this memory can not be changed afterwards.
- Read Only Memory is to be used in the conditions when we know that information needs not to be changed in future.
- ROM is of following types - – ROM (Read Only Memory) – PROM (Programmable Read Only Memory) – EPROM (Erasable Programmable Read Only Memory) – EEPROM(Electrically Erasable Programmable Read Only Memory)
- Storage Unit :
- It is essential to store data in computer for processing in future.
- Because Primary memory has its own drawbacks, secondary storage or storage unit is very much essential.
- Secondary storage is used to store more amount of data.
- Various secondary storage devices are available in market now a days - – Hard disk (Internal/External) – Pen drive – CD – DVD – Blue Ray Disks – Memory Cards – Magnetic Tapes
- System Bus :
- The group of wires used to connect main parts of Computer system is referred to System Bus that makes an electronic path for the transfer of data.
- System bus is needful for transfer of data & instructions between the various components of computer .
- The part of System bus that loads data is referred Data Bus.
- The part of System bus that loads instructions is referred control bus.
- The part of System bus which loads memory address is referred Address Bus.
- The bus connected with input/output units of system is referred I/O bus.
- Mobile System Organization :
- Modern Mobile is also like a miniature version of computer in hand.
- Although they have less processing power in comparison of computer system.
- We can perform following tasks with a mobile phone- – Calling – Photo taking with camera – To work on various apps by – touch screen facility – Watching videos – Listening audio (songs) – Playing games etc.
- Mobile phone receives power from battery.
- Mobile Processor :
- It is the brain of smartphone.
- It immediately responds on receiving a command.
- It has 2 main sub-processors- ~ Communication Processing Unit – It helps in making and receiving call on a mobile phone. It consists a digital signal processor that works with RF Transceiver & Audio subsystem. ~ Application Processing Unit (APU) – Helps in controlling each operation of mobile that is used in processing various applications . Another supporting unit is GPU (Graphics Processing Unit) that is responsible for handling all graphical applications & visuals of mobile phone.
- Now-a-days, every part of a mobile is placed on a single miniature chip that is known as System on a chip (SoC) it reduces energy consumption.
- Mobile Display sub-system :
- It is responsible for all tasks related to display and touch of screen. It supports the following tasks- – Display Screen – Touch Sensitive Interface – Touch Sensitive keyboard Camera sub-system
- The Mobile Display sub-system is based on image signal processing.
- It performs following tasks- – Instant Image Capture – High Resolution Support – Image Stabilization – Other image enhancements
- Mobile system memory :
- It is of 2 types-- – RAM, it is available in varieties of 2 GB, 4 GB, 6 GB, 8 GB. – ROM, it is available in varieties of 16 GB, 32 GB, 64 GB, 128 GB.
- Mobile Storage :
- It is an external expendable memory .
- It is formed in the form of SD cards & micro SD Cards.
- Mobile Power Management Subsystem :
- This subsystem provides power to mobile phone.
- Each mobile phone receives power from battery connected to it .
- It’s power is limited.
- Although it is required to charge battery after a certain time of it's usage.
- Software : Software is a set of programs which is designed for a special purpose.
- Hardware can not work without software.
- It works as an interface between hardware and a user . Due to it only a user can give directions to a hardware.
- Software gives directions to control various operations.
- Softwares are of 2 types- – System software – Application software
- System Software:
- A Software, that check inner operations of a computer system is called system software.
- It follows instructions related to a system & facilitates the uninterupted working of system.
- It is nearly impossible to work without system software.
- It works as an interface between hardware and a application software.
- It is further divided into 2 parts - – Operating system – Language processor
- Operating System : It is an interface between hardware and user.
- It acts like a manager of whole computer system.
- It controls all resources of hardware.
- It manages various application software with hardware.
- It forms an environment for the user where he/she can give commands and can receive outputs. Types of OS are - – Single User OS – Multi User OS – Time Sharing OS – Real Time OS – Multiprocessing OS – Distributed OS
- Language Processor : It is a special software which converts source code to object code or machine comprehendible code.
- Source code is a bunch of instructions written by a programmer using some computer programming language.
- Object code are those instructions that are received by translating source code in to machine comprehendible code.
- They can be used in the development of Softwares.
- Language Processor are of 3 types- – Assembler – Interpreter – Compiler
- Application Software : These are the software designed for some specific tasks.
- These are installed after installation of Operating-System .
- OS provides an environment to run an Application software.
- These are designed for a specific purpose.
- They are divided into 4 categories- – Packages (MS-Office) – Utilities (Text Editor, Paint Brush, Disk Defragmenter, Antivirus) – Customized Software (Tally, business software) – Developer Tool (software libraries)
🔔MORE MATERIALS TO BE UPLOADED STAY TUNED🔔
