Chapter 1: Computer Basics

Input devices

Devices that allow the computer to receive data and instructions from an external source.

Software

The programs that execute (i.e., run) on the hardware, carrying out tasks such as word processing or accessing the Web.

Computer

(Miles definition) An electronic machine operating under the control of instructions stored in its own memory which can accept data, manipulate data according to specified rules, produce results, and store the results for future use.

Graphical user interface (GUI)

A GUI (gooey) uses intuitive, visual elements to simplify the process of viewing files and executing programs. Although their organization and appearance may differ, most modern GUIs have similar features and behaviors.

Web page

A Web page is nothing more than a text document that contains additional formatting information in a language called HTML (HyperText Markup Language).

Software program

A collection of instructions for the computer (more specifically, the CPU) to carry out in order to complete some task.

File

A file is a document that stores information, such as text, an image, sound, or a program.

Hard disk

A form of secondary memory that is capable of permanently storing vast amounts of information (usually measured in gigabytes), which can be transferred into main memory (or primary memory, which is comprised of cache memory and RAM and holds an and all data that the CPU is actively using) when needed.

Cache memory

A memory technology that enables the fastest transfer of bits to and from the CPU because it uses electronic circuitry, where 1 and 0 are represented as the presence or absence of voltage over wires. Cache memory, which is usually built into the CPU chip itself, utilizes high-speed circuity to provide extremely fast access to data.

Random Access Memory (RAM)

A memory technology that enables the fastest transfer of bits to and from the CPU because it uses electronic circuitry, where 1 and 0 are represented as the presence or absence of voltage over wires. RAM, which is packaged on separate chips, communicates with the CPU using lower-speed circuitry; thus, data stored in RAM cannot be accessed as quickly as data in cache, but RAM is significantly less expensive to build.

Byte

Although the bit is the building block of digital memory, memory capacity is usually specified in bytes, which are collections of 8 bits that are capable of representing 2^N = 2^8 = 256 different values.

Web server

An Internet-enabled computer that executes software for providing access to certain Web documents. When you request a Web page, either by typing its name in your browser's Address box or by clicking a link, the browser sends a request over the Internet to the appropriate server. The server locates the specified page and sends it back to your computer.

Bits

Bits, or binary digits, are units of data that correspond to one of two potential values. Because bits represent one of only two possibilities, they are referred to as discrete values rather than continuous values, which are represented on a scale containing an infinite range of possibilities. Bits are the building blocks of digital memory.

Circuitry

Electronic components wired together to control the flow of electrical signals.

Stored-program computers

Computers that use the von Neumann architecture. These machines can initiate different tasks by retrieving different programs from memory.

Output devices

Devices that allow the computer to display or broadcast its results.

Systems software

In contrast to applications software, systems software manages the resources and behavior of the computer itself.

Memory

Memory stores information for the computer to process, as well as programs, or instructions specifying the steps necessary to complete specific tasks. It is essentially the part of a computer that stores programs and data.

Multitasking machines

Most modern computers are multitasking machines, meaning that more than one program can reside in main memory at the same time, sharing the CPU's resources.

von Neumann architecture

Named after computer science pioneer John von Neumann, this structure identifies three essential components that work together to function as a computer: input/output devices, memory, and a central processing unit (CPU). These three components are connected by buses, or collections of wires that carry information in the form of electrical signals. The von Neumann architecture enables multiple programs to reside in memory at the same time. Virtually all modern computers have this underlying structure.

Icons

Programs, directories, and files are represented as icons - small pictures that convey some aspect of the element they symbolize.

Kilobyte (KB)

Roughly 1,000 bytes of storage.

Megabyte (MB)

Roughly 1,000,000 bytes of storage.

Gigabyte (GB)

Roughly 1,000,000,000 bytes of storage.

Terabyte (TB)

Roughly 1,000,000,000,000 bytes of storage.

Applications software

Software designed to carry out tasks within a particular application area, such as word processing, graphical design, or Web access.

Central Processing Unit (CPU)

The CPU carries out programmatic steps in order to process data. In controlling the workings of the computer, the CPU has two key tasks: 1) fetching program instructions from memory, and 2) executing those instructions. CPU speed is generally measured in gigahertz (GHz), which indicates how many billions of instructions a CPU can execute in a second.

File system

The file system manages the computer's memory, organizing storage into files and directories.

Web browser

The job of Web browser is to access a Web page, interpret the HTML formatting information, and display the formatted page accordingly.

Operating system

The largest and most integral systems software stored on a computer is its operating system, a collection of programs that controls how the CPU, memory, and I/O, devices work together to execute programs. When a computer is turned on, or booted, a small part of the operating system is automatically loaded into memory. In turn, it loads other components of the operating system, which then execute continuously int eh background to control the workings of the computer.

Kernel

The most critical functionality of the computer is controlled by the component of the operating system known as the kernel, which manages the CPU'S operation, controlling how data and instructions are loaded from memory and accessed by the CPU. In addition to controlling the flow of programs and data between the CPU and memory, the kernel also coordinates other hardware components, allowing software applications to access memory and interact with the input/output devices. This allows a program being executed by the CPU to receive input from a keyboard, fetch data from a hard drive, display results on a screen, and even print the results to a laser printer.

Hardware

The physical components of the computer, such as the monitor, keyboard, and hard drive.

Directory

To make storage and retrieval easier for the user, memory is usually divided into directories (folders). A directory is a collection of files that are organized together and labeled with a common name.

Uniform Resource Locator (URL)

Web pages require succinct and specific names so that users can identify them and browsers can locate them. For this purpose, each page is assigned a URL. A URL begins with the protocol prefix http://, which specifies that the HyperText Transfer Protocol should be used in communications between the browser and server. The rest of the URL specifies the location of the desired page. Immediately following http:// is the server name, identifying the Web server on which the page is stored followed by the file name.

Protocols

Well-defined rules that define how pages are formatted. Protocols allow documents to be shared across networks on various types of computer, and essentially allow the World Wide Web to be operable.

Difference between the Internet and the World Wide Web

Whereas the Internet is made up of hardware (computers and the connections that allow them to communicate), the World Wide Web is a collection of software that spans the Internet and enables the interlinking of documents and resources.