1. Introduction to Computer System
Assistant Professor
Computer Engineering Department
Institute of Technology
Nirma University

2. Computer
It is an electronic device which accepts data from our outside world (standard input devices) and manipulates or process it according to instruction given at high speed.
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 retrieve data whenever required.
A computer follows a series of instructions, programmed into its memory by its user and outputs the information.
Difference between data and information?

3. Computer System Characteristics
Speed and accuracy
Diligence and maintainence
Vast storage media
Time factor
Permanent
Versatility

4. Applications of computer system
There are various areas where computer can be used:
Reservation system (air, railway, bus)
Banking system
Library management
Hospital management
Hotel management
Space technology
Weather forecasting

5. Computer Architecture

6. Hardware
Computer hardware is the collection of physical elements that constitutes a computer system.
Computer hardware refers to the physical parts or components of a computer such as the monitor, mouse, keyboard, computer data storage, hard drive disk (HDD), system unit (graphic cards, sound cards, memory, motherboard and chips), etc. all of which are physical objects that can be touched

7. Software
Computer software, or simply software, also known as computer programs, is the non-tangible component of computers.
It represents the set of programs that govern the operation of a computer system and make the hardware run.
Computer software contrasts with computer hardware, which is the physical component of computers.
Computer hardware and software require each other and neither can be realistically used without the other.
To help the computer to perform specific functions for itself. One major example is operating system. All computers require an operating system. E.g. OS ( Disk operating System, Windows, Linux, UNIX, Mac etc.)

8. Types of Software System Software Application 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.
General purpose
e.g. MS Office, Excel etc.
Specific purpose
Custom built according to requirement of user.

9. Register
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)

10. Central Processing Unit (CPU)
A central processing unit (CPU) is the hardware within a computer that carries out the 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 comparisons are done in this unit.
It takes data from memory unit and return information (process date) to memory unit if storage requires.

11. 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.

12. CPU

13. Bus and System Bus
In computer architecture, a bus is a communication system that transfers data between components inside a computer, or between computers.
This expression covers all related hardware components (wire, optical fiber, etc.) and software, including communication protocols.
Can be parallel or serial.

14. Bus and System Bus

15. Memory Unit 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
Secondary storage

16. Classification of Main Memory
Random Access Memory (RAM)
Stores current program or data.
Stores temporary data of current program.
Less space in comparison to secondary storage.
Volatile (data losses on power off)
Comparatively more expensive.
Fast in operation.
2. Read Only Memory (ROM)

17. 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 ms.
Sensitive to disturbances.
Slower and cheaper than SRAM.
Used in smartphones, tablets, laptops etc.

18. Read only Memory(ROM)
ROM is used for storing programs that are PERMENTLY resident in the computer and for tables of constants that do not change in value once the production of the computer is completed
The ROM portion of main memory is needed for storing an initial program called bootstrap loader, witch is to start the computer software operating when power is turned on

19. Types of Read only Memory (ROM)
PROM
PROM stands for Programmable Read Only Memory. This form of ROM is initially blank. The user or manufacturer can write data/program on it by using special devices. However, once the program or data is written in PROM chip, it cannot be changed. If there is an error in writing instructions or data in PROM, the error cannot be erased. PROM chip becomes unusable.
EPROM
EPROM stands for Erasable Programmable Read Only Memory. This form of ROM is also initially 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 and ultraviolet rays. So program or data written in EPROM chip can be changed and new data can also be added. When EPROM is in use, its contents can only be read.
EEPROM
EEPROM stands for Electrically Erasable Programmable Read Only Memory. This kind of ROM can be written or changed with the help of electrical devices. So data stored in this type of ROM chip can be easily modified.

20. Secondary Memory 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

21. Input Devices
Accept data and instructions from the user or from another computer system

22. KeyBoard
Mouse

23. Scanner
Joy Stick

24. Light Pen
Web Camera

25. Touch Screen
Mike

26. Output Devices
Return Processed data back to the user or other computer system

27. Laser Printer
Ink Jet Printer

28. Dot Matrix Printer
Line Printer

29. Speakers
Monitor

30. Classification of programming languages
Machine or Low level language
Assembly language
High level language

31. Compiler
Compiler is a computer program (or set of programs) that transforms source code written in a programming language (the source language) into another computer language (the target language, often having a binary form known as object code). The most common reason for wanting to transform source code is to create an executable program.
The name "compiler" is primarily used for programs that translate source code from a high- level programming language to a lower level language (e.g., assembly language or machine code).
If the compiled program can run on a computer whose CPU or operating system is different from the one on which the compiler runs, the compiler is known as a cross-compiler.
A program that translates from a low level language to a higher level one is a decompiler.
A program that translates between high-level languages is usually called a source-to-source compiler.
A language rewriter is usually a program that translates the form of expressions without a change of language. More generally, compilers are sometimes called translators.

32. Interpreter
A translating program that translates and executes the statements in sequence
Assembler or compiler produce machine code as output, which is then executed in a separate step i.e. translates line by line conversion of high level language into low level programs.
An interpreter translates a statement and then immediately executes the statement
Interpreters can be viewed as simulators

33. Compilers
How does this differ from
the assembly process?

34. Assembler
An assembler is a program that takes basic computer instructions (assembly language) and converts them into a pattern of bits (machine language) that the computer's processor can use to perform its basic operations.
e.g. Microprocessor 8085, 8088.
Instruction: ADD R1, R2

35. Operating System(OS)
Operating System is a software, which makes a computer to actually work.
It is the software the enables all the programs we use.
The OS organizes and controls the hardware.
OS acts as an interface between the application programs and the machine hardware.
Examples: Windows, Linux, Unix and Mac OS, etc.,

36. What OS does? controlling and allocating memory,
An operating system performs basic tasks such as,
controlling and allocating memory,
prioritizing system requests,
controlling input and output devices,
facilitating networking and
managing file systems.

37. Structure of Operating System:
Application Programs
System Programs
Software (Operating System)
HARDWARE

38. Structure of Operating System:
The structure of OS consists of 4 layers:
Hardware
Hardware consists of CPU, Main memory, I/O Devices, etc,
Software (Operating System)
Software includes process management routines, memory management routines, I/O control routines, file management routines.
System programs
This layer consists of compilers, Assemblers, linker etc.
Application programs
This is dependent on users need. Ex. Railway reservation system, Bank database management etc.

39. Homework
Generation of computers – Comparison