Introduction to Computer System

Computer Generations

Computer Architecture

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

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.

• System Software- To help the computer to perform specific functions for itself. One major example is operating system. All computers require an operating system. E.g. DOS ( Disk operating System, Windows 98, Windows 2000, Windows XP, Windows NT, Linux, UNIX etc.)

Bus and System Bus

• In computer architecture, a bus (from the Latin omnibus, meaning "for all") 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.[1]

• Early computer buses were parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same logical functionality as a parallel electrical bus.

• Modern computer buses can use both parallel and bit serial connections, and can be wired in either a multidrop (electrical parallel) or daisy chain topology, or connected by switched hubs, as in the case of USB.

Bus and System Bus

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)

Stack Pointer (SP)

Accumulator

CPU, ALU and MPU

• A central processing unit (CPU) (formerly also referred to as a central processor unit[) 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.

• The term has been in use in the computer industry at least since the early 1960s. The form, design, and implementation of CPUs have changed over the course of their history, but their fundamental operation remains much the same.

• A computer can have more than one CPU; this is called multiprocessing. All modern CPUs are microprocessors, meaning contained on a single chip. Some integrated circuits (ICs) can contain multiple CPUs on a single chip; those ICs are called multi-core processors. An IC containing a CPU can also contain peripheral devices, and other components of a computer system; this is called a system on a chip(SoC).

• Two typical components of a CPU are the arithmetic logic unit (ALU), which performs arithmetic and logical operations, and the control unit(CU), which extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.

CPU

Main Memory

• Commonly known as random access memory, or just RAM

• Holds instructions and data needed for programs that are currently running

• RAM is usually a volatile type of memory

• Contents of RAM are lost when power is turned off

Classification of Main Memory

1. Random Access Memory (RAM)

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.

• 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.

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

Read only Memory(ROM)

Types of Rom:

ROM

PROM (Programmable read-only memory)

EPROM (Erasable programmable read-only memory)

EEPROM (Electrically erasable programmable read-only memory)

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

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Input Devices

• Accept data and instructions from the user or from another computer system

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KeyBoardMouse

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Scanner Joy Stick

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Light PenWeb Camera

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Touch ScreenMike

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Output Devices

Return Processed data back to the user or other computer system

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Laser Printer Ink Jet Printer

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Dot Matrix PrinterLine Printer

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SpeakersMonitor

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 or transpiler.

• 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.

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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

• An interpreter translates a statement and then immediately executes the statement

• Interpreters can be viewed as simulators

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Compilers

Figure 9.2 Compilation process How does this differ from

the assembly process?

Assembler

• An assembler is a program that takes basic computer instructions and converts them into a pattern of bits that the computer's processor can use to perform its basic operations.

High Level Languages / Low Level Languages

High Level Languages / Low Level Languages

• In computer science, a high-level programming language is a programming language with strong abstraction from the details of the computer.

• In comparison to low-level programming languages, it may use natural language elements, be easier to use, or may automate (or even hide entirely) significant areas of computing systems (e.g. memory management), making the process of developing a program simpler and more understandable relative to a lower-level language.

• The amount of abstraction provided defines how "high-level" a programming language is.

High Level Languages / Low Level Languages

• In computer science, a low-level programming language is a programming language that provides little or no abstraction from a computer's instruction set architecture.

• Generally this refers to either machine code or assembly language.

• The word "low" refers to the small or nonexistent amount of abstraction between the language and machine language; because of this, low-level languages are sometimes described as being "close to the hardware".

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.,

What OS does?

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.

Structure of Operating System:

Application Programs

System Programs

Software (Operating System)

HARDWARE

Structure of Operating System (Contd…):

The structure of OS consists of 4 layers:1. Hardware

Hardware consists of CPU, Main memory, I/O Devices, etc,

2. Software (Operating System)Software includes process management routines, memory management routines, I/O control routines, file management routines.

Structure of Operating System (Contd…):

3. System programs

This layer consists of compilers, Assemblers, linker etc.

4. Application programs

This is dependent on users need. Ex. Railway reservation system, Bank database management etc.,

Executable Statements

• Arithmetic, logical, statement label (ASSIGN), and character assignment statements

• Unconditional GO TO, assigned GO TO, and computed GO TO statements

• Arithmetic IF and logical IF statements

• Block IF, ELSE IF, ELSE, and END IF statements

• CONTINUE statement

• STOP and PAUSE statements

• DO statement

• READ, WRITE, and PRINT statements

• REWIND, BACKSPACE, ENDFILE, OPEN, CLOSE, and INQUIRE statements

• CALL and RETURN statements

• END statement

Non executable Statements

• PROGRAM,

• FUNCTION,

• SUBROUTINE

• ENTRY