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Prof. Anuja Nair
Computer Engineering Department
Institute of Technology
It is an electronic device which accepts data from our outside world (standardinput devices) and manipulates or process it according to instruction given at highspeed.
It has memory to store large amount of data and can process it in accurate form.
Computer is also called data processor because it can store, process and retrievedata whenever required.
A computer follows a series of instructions, programmed into its memory by itsuser and outputs the information.
Difference between data and information?
Computer System Characteristics
Speed and accuracy
Diligence and maintainence
Vast storage media
Applications of computer system
There are various areas where computer can be used: Reservation system (air, railway, bus)
Generation of computers
Refer the document Generation of computers uploaded on blog.
Computer hardware is the collection of physical elements that constitutesa computer system.
Computer hardware refers to the physical parts or components of a computer such asthe monitor, mouse, keyboard, computer data storage, hard drive disk (HDD), systemunit (graphic cards, sound cards, memory, motherboard and chips), etc. all of which arephysical objects that can be touched
Computer software, or simply software, also known as computer programs, is thenon-tangible component of computers.
It represents the set of programs that govern the operation of a computer system andmake the hardware run.
Computer software contrasts with computer hardware, which is the physicalcomponent of computers.
Computer hardware and software require each other and neither can be realisticallyused without the other.
To help the computer to perform specific functions for itself. One major example isoperating system. All computers require an operating system. E.g. OS ( Disk operatingSystem, Windows, Linux, UNIX, Mac etc.)
Types of Software
System Software To control operation and extend the processing capabilities of computer system.
e.g. Operating System, Compiler, Assembler, etc.
Application Software Designed for user specific need.
e.g. MS Office, Excel etc.
Custom built according to requirement of user.
Compiler : translates high level language to machine level language
Assembler : translates assembly or low level language to machine language
Loader : which loads OS part and object program into main memory for executionpurpose. E.g. bootstrap loader.
Linker : which binds code of source and library file to make executable programs.
Editor : used to write a program.
Translator : which converts one language into other. (Compiler, Assembler, Interpreter)
Macro processor : Replace symbolic meaning into equivalent code. Also, called pre-processor.
Interpreter : translates line by line high level language into machine language.
System software vs. Application softwareSr. No. Particular System software Application software
1. Purpose Comprises of those programs whichdirects the computer.
It is the software developed forsolving business problems.
Varies from computer to computer. Varies from organization toorganization.
3. Language Written in low-level language. Written in high level language.
4. Knowledge Detail knowledge of hardware isrequired.
Requires detailed knowledge oforganization.
5. Use Use to improve the performance andmaximum utilization of systemresources.
Use to improve speed and quality of abusiness activity.
The manufactures along with thehardware usually supply systemsoftware.
Developed by individuals or suppliedby software vendors as generalizedapplication software.
Hardware register, a placeholder for information about some hardware condition
Processor register, a component inside a central processing unit for storing information
e.g. Program Counter (PC)
Central Processing Unit (CPU)
A central processing unit (CPU) is the hardware within a computer that carries outthe instructions of a computer program by performing the basic arithmetical, logical,and input/output operations of the system.
CPU is a combination of ALU (arithmetic logic unit) and CU (Control Unit).
ALU Here actual execution instruction takes place during processing operation.
It performs all arithmetic calculations and takes logical decision.
It can compare, count, shift or other logical activities. All such calculations and comparisonsare done in this unit.
It takes data from memory unit and return information (process date) to memory unit ifstorage requires.
Central Processing Unit (CPU)
CU It manages and coordinates operations of all other components of computer system. It also
performs following functions:
It retrieves instruction or data from memory.
It decodes instruction.
It coordinates time sequence of instruction among various component of system.
It determines requirement of storage and take action according to it.
It also fetches instruction from main memory.
Bus and System Bus
In computer architecture, a bus is a communication system that transfers data betweencomponents inside a computer, or between computers.
This expression covers all related hardware components (wire, optical fiber, etc.) andsoftware, including communication protocols.
Can be parallel or serial.
Bus and System Bus
Storage unit for processing data and information.
Holds instructions and data needed for programs that are currently running
Two types of storage: Primary/Main storage
Classification of Main Memory
1. Random Access Memory (RAM)1. Stores current program or data.
2. Stores temporary data of current program.
3. Less space in comparison to secondary storage.
4. Volatile (data losses on power off)
5. Comparatively more expensive.
6. Fast in operation.
2. Read Only Memory (ROM)
Random-Access Memory (RAM) Static RAM (SRAM)
Each cell stores bit with a six-transistor circuit.
Retains data, as long as it is kept powered.
Relatively insensitive to disturbances such as electrical noise.
Faster (8-16 times faster) and more expensive (8-16 times more expensive as well) than DRAM.
Used in cache of the processor.
Dynamic RAM (DRAM) Each cell stores bit with a capacitor and transistor.
Data must be refreshed every 10-100 ms.
Sensitive to disturbances.
Slower and cheaper than SRAM.
Used in smartphones, tablets, laptops etc.
Read only Memory(ROM)
ROM is used for storing programs that are PERMENTLY resident in the computerand for tables of constants that do not change in value once the production of thecomputer is completed
The ROM portion of main memory is needed for storing an initial program calledbootstrap loader, witch is to start the computer software operating when power is turnedon
Types of Read only Memory (ROM)
PROM stands for Programmable Read Only Memory. This form of ROM is initially blank. Theuser or manufacturer can write data/program on it by using special devices. However, once theprogram or data is written in PROM chip, it cannot be changed. If there is an error in writinginstructions or data in PROM, the error cannot be erased. PROM chip becomes unusable.
EPROM stands for Erasable Programmable Read Only Memory. This form of ROM is alsoinitially blank. The user or manufacturer can write program or data on it by using special devices.Unlike PROM, the data written in EPROM chip can be erased by using special devices andultraviolet rays. So program or data written in EPROM chip can be changed and new data canalso be added. When EPROM is in use, its contents can only be read.
EEPROM stands for Electrically Erasable Programmable Read Only Memory. This kind of ROMcan be written or changed with the help of electrical devices. So data stored in this type of ROMchip can be easily modified.
A nonvolatile storage medium
Contents retained while power is off
Hard disk drives are most common Records data magnetically on a circular disk
Provides fast access to large amounts of data
USB flash memory devices High capacity device plugs into USB port
Portable, reliable, and fits easily in a pocket
e.g. Hard disk (HDD), CD, DVD, Pen Drive, Removable hard disk
Accept data and instructions from the user or from another computer system