Chapter 1 Introduction

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History of Computers

Development of computers began with many early inventions: The abacus helped early societies perform computations (c. 3000 B.C.

) The Pascaline used moveable dials to add numbers with up to eight digits (1642).

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Nineteenth-Century Inventions

The nineteenth century brought further inventions: Charles Babbage’s Difference Engine and later his Analytical Engine defined many basic components of today’s computers.

The arithometer (1820) performed four basic mathematical functions: + - * /.

Herman Hollerith developed a system to aid in tabulating data from the 1890 U.S. Census using punch cards.

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First-Generation Computers

During World War II, the first generation of modern computers was introduced: Colossus was developed in England to decode encrypted German messages.

ENIAC was developed in the U.S. to calculate ballistic missile trajectories.

EDVAC was designed by John Von Neumann and it featured a central processing unit.

UNIVAC was the first commercially available computing device.

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Second-Generation Computers

The second generation of computers (c. 1956) was marked by: A shift from bulky vacuum tubes to transistors. A shift in programming from physically rerouting cables to “software” stored on punch cards and tape storage.

The emergence of machine and assembly languages.

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Third-Generation Computers

With the invention of integrated circuits (ICs), computers became smaller and more powerful. ICs: Are smaller than transistors Produce less heat Allow multiple components to fit on a smaller chip

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Fourth-Generation Computers

Computers became smaller and more affordable, and available to small businesses and individuals.

MITS Altair 8800 (1974) Apple I, II Commodore PET IBM PC (1981) Macintosh (1984)

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What is computer hardware?

Computer hardware are the physical components of the computer.

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Input/Output Devices

Input/Output devices provide communication between user and hardware.

Input Devices Keyboard Mouse Scanner Output Devices Monitor Speakers Printer

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Processors and Memory

Central Processing Unit (CPU) Performs basic functions, millions and billions of times per second (brains of the computer) Random-Access Memory Stores data used by the CPU (before and after processing)

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Data Storage

Data storage uses a variety of media. Capacity is measured in bits and bytes: A bit represents the on or off state of a transistor (symbolized by a 1 or a 0).

A byte is eight bits.

A kilobyte is 2 10 or 1,024 bytes.

A megabyte is 1,048,576 bytes.

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Hard Drives

The hard drive is the primary storage device in a computer. Hard drives are: Long term, rewritable storage Large capacity Inexpensive Fixed media (relatively difficult to move from one computer to another)

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Removable Media

Some storage devices are more portable: CD/DVD Medium capacity Inexpensive Easy to transport from one computer to another Flash, Zip, USB drives Differing capacities Differing price per MB

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Computer Software

Software can be divided into two categories: Systems software includes operating systems, compilers, and utilities.

Application software runs on top of an operating system.

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What is an operating system?

An operating system (OS) manages the hardware and software on a computer system. An OS: Manages memory and hardware resources Allocates resources to applications Provides a consistent interface for applications

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Operating Systems

UNIX/Linux Multiuser OS Multitasking Runs on many types of hardware Modular tools Mac OS First mainstream graphical user interface Icons (pictures) and mouse replaced command line interface DOS/Windows DOS gained popularity with first PCs Windows provided graphical interface to DOS Windows later separated itself from DOS underpinnings

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Applications

Desktop Software Installed on single computer Most common type of application in use today Web-Based Software Runs on a Web server, accessed through a browser Accessible anywhere one has access to the Internet Web Services Allow applications to communicate with each other without user intervention

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Low-Level Languages

Low-level programming languages use simple commands to communicate with the CPU: Machine language (most basic language of the CPU) Assembly language (human readable, but close to machine language)

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High-Level Languages

High-level languages can be procedural or object-oriented: Procedural languages use a step-by-step process to solve a problem.

Basic, Pascal, C Object-oriented languages model problems using objects that correspond to real-world counterparts.

Smalltalk, C++, Java

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Software Development Process

Software development usually follows these basic steps: Analysis Design Implementation Testing Deployment Maintenance