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Chapter 1. Introduction. 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). Nineteenth-Century Inventions.
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Chapter 1 Introduction
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).
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.
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.
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.
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
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)
What is computer hardware? • Computer hardware are the physical components of the computer.
Input/Output Devices • Input/Output devices provide communication between user and hardware. • Input Devices • Keyboard • Mouse • Scanner • Output Devices • Monitor • Speakers • Printer
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)
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 210 or 1,024 bytes. • A megabyte is 1,048,576 bytes.
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)
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
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.
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
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
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
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)
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
Software Development Process • Software development usually follows these basic steps: • Analysis • Design • Implementation • Testing • Deployment • Maintenance