How Computers Work

Clock

A microchip that REGULATES the timing and speed of all the computer's functions. The chip includes a crystal that vibrates at a certain frequency when electricity is applied to it. The shortest length of time in which a computer can perform some operation is one clock, or vibration of the clock chip. The speed of clocks - and therefore computers - is expressed in megahertz (MHZ). One megahertz is 1 million cycles, or vibrations, a second. Thus, a PC can be described as having a 200 or 300 MHz processor, which means that the processor has been designed to work with a clock chip running at that speed.

Gate

A microcircuit design in which transistors are arranged so the value of a bit of data can be changed.

Transistor

A microscopic switch that controls the flow of electricity through it, depending on whether a different electrical charge has opened or closed the switch -> A type of switch that contains no moving parts and uses electricity to turn itself on and off

Algorithm

A procedure, rule, or formula for solving a problem. A computer program is essentially an elaborate algorithm that goes through a series of steps to arrive at a specific outcome.

Complex Instruction set computing (CISC)

A processor architecture design in which large, complicated instructions are broken down into smaller tasks before the processor executes them.

SIMD (Single Instruction Multiple Data)

A processor architecture that allows the same operation to be performed on multiple pieces of data simultaneously.

Reduced Instruction Set Computing (RISC)

A processor design in which only small, quickly executing instructions are used. Contrast to complex instruction set computing.

Call

A programming command that uses - calls on - a specific routine elsewhere in the program in a .DLL file (Dynamic Link Library file). After the routine ended, execution returns to the point in teh code where the call happened.

Loop

A section of software commands that returns to its beginning and runs again as long as no specific condition has been encountered.

Machine Language

A series of codes, represented by numbers (0's and 1's), used to communicate directly with the internal instructions of the PC's microprocessor.

Register

A set of transistors in a processor where data is stored temporarily while the processor makes calculations involving that data - a sort of electronic scratch pad.

Motherboard

A sheet of plastic onto which metallic circuits have been printed and to the rest of the PC's components are connected. These components could be connected via a socket, such as a CPU, or they may be built directly onto the motherboard, as with external ports, such as USB.

Microchip

A sheet of silicon dioxide (wafer) where microscopic electrical circuits have been etched using a system of light, light-sensitive films, and acid baths.

Bootstrap

A small amount of code that's a permanent part of the PC, simply to boot up the computer (the two tasks being: run a power-on self-test (POST), and the other to retrieve the Operating system from the bard drive to put in RAM). It lets the PC do something entirely on its own, without any outside operating system.

Compiler

A software tool that converts source code into a format that can run only with the assistance of an operating system. Compiled into an executable once, then run whenever necessary.

Interpreter

A software tool that converts source code on the fly into instructions the computer can understand. Done every time the program is run.

CPU

"Central Processing Unit" - it is used to mean microprocessor - also processor - which is a microchip that processes the information about the code (instructions) used by the computer. The "brains" of a computer.

RAM

"Random Access Memory" - memory or disks that can be both read and written to.

ROM

"Read Only Memory" - memory chips or data stored on disks that can be read by the computer's processor. The PC cannot write new data to those chips or disk drives.

USB Ports

"Universal Serial Bus" Ports - solution to PC's lack of system resources to let software connect directly to peripherals (Device connected to a host computer that is not part of it).

Writing Data to RAM

A transistor is essentially a microscopic electronic switch. In RAM, an electrical pulse turns on (closes) a transistor that's connected to a data line at each memory location in a RAM chip where data can be stored. While the transistors are turned on, the software sends bursts of electricity along selected data lines. Each burst represents a 1 bit. The pulse charges a capacitor (This process repeats continuously to refresh the capacitor's charge. Each charged capacitor along the address line represents a 1 bit, the uncharged capacitor represents a 0 bit. The PC uses 1 and 0 bits as binary numbers to store an manipulate all information, including words and graphics.

Process of a Compiler

A compiler is made up of a Lexer, a program that strips all unnecessary parts from the code. Next, the parser converts the tokens made by the Lexer into nodes on a syntax tree that represent the logical flow of the program. Then, the code generator produces segments of machine code for each tree node. Finally, the optimizer inspects the code produced by the code generator, looking for redundancies, making the final compiled program smaller and faster.

Capacitor

A component that stores an electrical charge.

Pipelining

A computer architecture designed so that all parts of a circuit are always working, and that no part of the circuit is stalled - writing data from another part.

Game Engine

A computer game's master program that coordinates all the other components such as graphics, sound, calculating, and physics.

Multithreaded

A type of program designed to take advantage of Intel's processors' ability to execute more than one string of data - thread - at the same time. Multithreaded programs must be designed so the threads can run independently and will not interfere with each other.

Beta Versions, or Beta

A working version of a program being developed in which most of the components work. A company often sends betas to its customers, who try to find bugs in the beta. A program might go through several betas before being released to the public.

Virtual Machine

A computer rendered entirely in software.

Pin Grid Array (PIG)

A connection arrangement of microchips that features plug-in electrical terminal pins arranged in a matrix format, or an array.

Flow Chart

A diagram that depicts the flow of a program.

Bug

A flaw in software that causes the program to malfunction or freeze when it encounters specific situations.

Module

A generic term for self-contained sections of a program that perform specialized function, such as a spell checker.

The Windows Registry

Hierarchical database of configuration settings that controls all aspects of how Windows looks and works. Many of the menus and dialog boxes you use to configure Windows and Windows Programs are only front ends for modifying the Registry. The Registry can be modified with the Registry Editor or programs you download from the internet (safer). There are 5 main Keys, with many sub-keys and 5 primary data types.

Wafer

In a semiconductor technology, a very thin piece of silicon that functions as the base material for building microchips. Also called a "slice"

How Hardware tells the CPU what to do

In computers, interrupts are the preferred method of handling requests from software and hardware. 1) When you press the A key, an electrical signal travels along a circuit, which serves to identify what key you pressed, to the keyboard controller. 2) The Keyboard interrupt arrives on one of 16 interrupt request lines (IRQ) 3) The controller relays a signal to a subsystem called the interrupt controller, which runs interference between the CPU and 256 possible kinds of noteworthy interrupts. 4) The interrupt controller sends a signal to one of the pins sticking out of the bottom of the CPU called the INTR, used for normal interrupt signals. 5) The CPU puts what it was doing on hold, writes a memory address to a stack. (this serves to remind the CPU where it left off from its previous task). 6) CPU checks another pin to find out what key you pressed, and checks a section of memory called interrupt descriptor table (IDT). The CPU performs instructions (interrupt service routine ISR) at one of the IDT's locations associated with the A key. 7) When ISR completes its job, it sends a return from interrupt (RET) instruction to the CPU. That tells the CPU it is free to return to whatever it was doing before it was interrupted. It pulls the last memory location off the stack, and continues working.

Logic Design

Techniques used to connect logical building locks or primitives (that is, AND gates, OR gates, and so on) to perform a logical operation.

Arithmetic Logic Unit (ALU)

The central part of a microprocessor that manipulates the data received by the processor.

Software working with Hardware

Software programs writes a command to the O.S. for dealing with parts of the computer. For example, saving a file to the disk drive in a word processor. Windows turns over the job of saving the document to the BIOS and Driver. The controller mechanism translates the instructions from the BIOS/driver into the electrical signals that move the drive's read/write heads to the proper locations on the disk and that create the magnetic signals to record the document's data onto the disk's surface.

Reading Data from RAM

Software sends electrical pulse to address line, closing transistors connected to it. Everywhere along the address line where a capacitor is holding a charge, the capacitor will discharge through the circuit created by the closed transistors, sending electrical pulses along the data lines. The software recognizes from which data lines the pulses come from and interprets each pulse as a 1, and any line lacking a pulse as a 0.

Operating System

Software that exists to control the operations of hardware. Essentially, the operating system directs any operation, such as writing data to memory or to disk, and regulates the use of hardware among several application programs running at the same time.

Application

Software that performs a specific function that is the end result of using the computer. Word Processors, Database programs, Web browsers, and image-editing programs are all applications.

Pin

In plastic and metal wafer carriers, a protrusion of the wafer that fits into a matching hole in the wafer carrier of alignment then wafers are transferred.

System Bus

Includes all of the circuits printed on and into the motherboard.

Offset

The current position of the interpreter when parsing a code file.

Interface

The design of a program that determines how a computer user interacts with software. The two most common interfaces are graphical user and text interface, which consists of typing command words (command line).

Parsing

The joining, deletion, or extraction of some text characters to use them elsewhere in the program.

The Motherboard

The motherboard is the uniting element among all the chips and circuitry that make up a computer. Devices communicate with each other through the motherboard's circuits, from which they also draw their power. Motherboards come in different form factors that align the board with different sizes and styles of computer cases. They also come with different sockets that determine what types of chips and expansion boards they can accept.

Bus

To send data to any of the other motherboard components - a write operation - the microprocessor, or another component, raises the voltages of a combination of 24 of the traces that make up the address bus. This combination of traces (or lines) is the unique address of something on the internal bus, such as a location in memory; one of the components located on the motherboard itself; or a device. The process puts the data it wants to write on a bank of electrical traces, the data bus, by raising the voltages on some to represent ones and leaving voltages unchanged on others to represent zeros.

Expansion Slot

Unused Slots into which the owner can plug circuit boards and hardware to add to the computer's capabilities.

How Windows shares data on the clipboard

When a user copies selected text, three formats are saved. One in the original format, a bitmap format, and a metafile format. Depending where the user pastes of uses that copy (another program) the program uses one of the three formats.

Write and Read

Writing is the process by which a computer stores data in either RAM chips or on a disk drive. Reading is the process by which a computer transfers data or software code from a drive to RAM or from RAM to the microprocessor.

Boolean Operations

Logical operations, based on whether a statement is true of false, that are equivalent of mathematical operations with numbers. 1 = true, 0 = false.

AI (Artificial Intelligence)

AI is used in games for everything from making a computer opponent behave like a human opponent to having automated units perform tasks in a realistic manner.

ASCll

Acronym for American Standard Code of Information Interchange

Power-On Self-Test

BIOS tests the computer's components to make sure they are present and functioning properly. The BIOS uses the information on the CMOS to test the validity of the responses. The BIOS then instructs the CPU to read code stored at various locations (of the motherboard from different components) and compares what it finds to identical records stored permanently in the BIOS chip set. The BIOS loads into memory the device drivers and interrupt handlers from the basic hardware in the system, such as the keyboard, mouse, hard drive, etc. To be sure all the PC's operations function in a synchronized, orderly fashioned, the CPU also checks the system's timer. The BIOS has the CPU send signals over the system bus to be sure all the basic components are functioning. Several other steps.

Drain

the part of a transistor where electrical current flows out when it is closed.

Resistors

Resistors clamp down on electricity before it has the chance to burn up the rest of the components.

Adder, half-adder, full-adder

Differing combinations of transistors perform mathematical and logical operations on data being processed. (half-adder = and and xor logical gate) (full-adder = half-adder with additional logical gates)

How a Disc Boot Wakes Up Your PC

1) After conducting POST check of all hardware components of PC, the boot program contained on the computer's ROM BIOS tells the processor to execute a program contained in the C: hard drive's boot sector. That code, NTLDR, tells the processor where to find more code on the drive. 2) The list of all the system's hardware is passed to the Windows registry, where other programs have access to the information. 3) The registry loads several low-level programs into memory. These programs load other programs that windows quickly assimilates as parts of an O.S. 4) WIth enough files located to handle basic hardware operations, Windows loads Plug and Play's enumerator. This process also loads drivers for the PCI bus. 5) To prepare the computer to hold gigabytes of new files, the O.S. loads support for hard drives, maintains disk partitions, and officially mounts the drives for use. 6) With drive support loaded, O.S. loads special video drivers for such components as a PCI-Express video card. 7) Services are loaded from the hard drive to memory, and include essentials such as disk defragging and partition management. 8) When the services have all been installed and begin doing their jobs, we finally see the Windows logo onscreen. The O.S. is ready to get to work!

How Plug and Play Works

1) BIOS searches and identifies all devices the system needs. Then passes control to the operating system. 2) Configuration manager in windows adds to itself special device drivers called enumerators (programs that act as the interface between the operating system and the different devices(usually multiple)). 3) Windows stores info from enumerators in hardware tree, database stored in RAM. Then decides what resources to allocate to which device. 4) O.S. searches for appropriate device driver for each device. If it doesn't find the driver, the O.S. prompts you to install it. O.S. then loads all necessary device drivers and tells each driver which resources its device is using. The device drivers initialize their respective devices, and the system finishes booting.

Cache

A block of high-speed memory where data is copied when it is retrieved from RAM. Then, if the data is needed again, it can be retrieved from the cache faster than from RAM. A "Level 1" cache is located on the CPU die. A "Level 2" cache is part of the processor die or packaging.

Logic

A collection of circuit elements that perform a function, especially a set of elements that use digital logic and perform Boolean logic functions.

BIOS (basic input / output system)

A collection of software codes build into a PC that handle some of the fundamental tasks of sending data from one part of the computer to another. When the computer is first turned on, it provides enough code to wake up the rest of the hardware. Primary arbitrator between Windows and hardware.

Megahertz (MHz)

A measurement, in millions of the number of times something oscillates or vibrates. Processor speeds are normally measured in gigahertz (GHz)

Graphic User Interface (GUI)

A method of controlling software using onscreen icons, menus, dialog boxes, and objects that can be moved or re sized, usually with a pointing device such as a mouse.

Micrometer

A metric unit of linear measure that equals 1 / 1,000,000 meter, or 10,000 angstroms. The width of microprocessor circuits are measured in micrometers. The diameter of human hair is approximately 75 micrometers. Also called "micron"

CMOS

An acronym for "complementary metalox semiconductor" - a term that describes how a CMOS microchip is manufactured. The CMOS chip retains crucial information about what hardware a PC comprises even when power is turned off.

Address Line

An electrical line, or circuit, associated with a specific location in RAM.

Data Line

An electrical line, or circuit, that carries data; specifically in RAM chips, a circuit that determines whether a bit represents a 0 or 1.

Ports

An input/output panel holds the miscellaneous ports on the back and front of the PC that are used for communicating with external devices.

Code Tokens

An interpreter parsing a program turns the command and parameters of a line of code into code tokens. These are short abbreviations for instructions that are passed to the microprocessor, which carries out the instructions. If a line of code validates by the interpreter, the interpreter executes that line.

Difference between Interpreter and Compiler

An interpreter translates the source code, line by line, each time the source program is run. A compiler translates the entire source code into an executable file that a specific type of computer, such as a PC or Mac, runs without the need of an interpreter.

Dialog Box

An onscreen display that allows a computer user to select among several choices to determine how a program should operate.

PCI-Express

Bus architecture that uses both parallel and serial transfers. It breaks data into packets and has them travel on lanes (2 pairs of lines carrying packets) between various components. Route would include CPU -> North Bridge -> Memory. CPU -> South Bridge -> Chip (I/O)

Capacitors

Capacitors consume great amounts of electrical charge, holding it in so other components can have a steady supply or sudden surge of electricity when they need it.

Drivers

Coded instructions for a specific hardware peripheral contained in a file and copied to the computer when that device is installed. Drivers translate commands from the operating system and BIOS into instructions for a specific piece of hardware, such as a printer. Most Drivers are loaded when the O.S. is loaded, and become seamless extensions of the BIOS.

Dynamic Link Library (DLL)

Collections of code housed in the same DLL file that can be used by more than one program. The perform common software functions. (O.S. library in a way)

Byte

Combination of 1's and 0's from eight data lines.

Circuit Traces

Connecting all parts of the motherboard, with stripes of copper and aluminum.

Binary

Consisting of only two integers, 0 and 1. Binary math is the basis for manipulating all data in computers.

Microchips

Contain millions of transistors.

Transistor

Essentially a vacuum tube buit on a microscopic scale. Because its small, a transistor requires less power to generate a flow of electrons. Because it uses less power, it generates less heat and makes computers more dependable and allows them to be smaller. All microchips are basically vast collections of transistors - switches - arranged in different patterns so that they accomplish different tasks.

Software Applications

Generally, complex software consists of one file that contains a master program - the kernel - surrounded by a collection of files that contain subprograms, or routines. The kernel calls the routines it needs to perform some task. A routine can also call other routines in different files. Together, the kernel and subprograms give programs a way to receive, input, information from the keyboard, memory, ports, and files, and a way to send, or output, information to the screen, memory, ports, and files.

Low-level language

Software code written with specialized words that bear little resemblance to ordinary language but which require less interpretation or compilation to create a finished program.

Semiconductor

Materials (such as silicon) that can be altered to either conduct electrical current of block its passage. Microchips are typically fabricated on semiconductor materials such as silicon, germanium, or gallium arsenide.

Dual-Line memory modules (DIMMs)

Memory chips grouped together on small circuit boards. Most of the components in a PC are mounted on printed circuit broads. The motherboard is the largest printed circuit.

Circuit Board

Originally, wires ran from and to any component in any electrical device. A Circuit board replaces the need for separate wiring with the metallic traces printed on the board. The traces lead to connections for processors, resistors, capacitors, and other electrical components.

Printed Circuits

Printed circuits eliminate the need for individual wires that connect components and also greatly reduce the time and cost of building a PC by doing away with hand-soldering of most connections. Chips are placed into sockets on the motherboard. Chips that likely will not be replaced are surface mounted and soldered directly to the traces that carry signals to and from the chips. Gold plated (to resist tarnish) connectors allow daughter boards to be inserted into sockets on the motherboard. Capacitors and resistors stabilize the flow of current and half remove static and electrical surges and drops.

Chip Set (North and South Bridge)

Second only to the processor in determining the performance and capabilities of a PC. The chip set bridges logical and physical gaps between the CPU and other chips, at all times watching and controlling the input and output of specific components. North Bridge - provides controls the computer's graphics, RAM, and front side bus (main highway for data connecting graphics and memory to the CPU). Crucial part of the North Bridge is a memory controller, which constantly renews the memory modules. South Bridge - in charge of input/output with the disk drives, audio, networking, universal serial port (USB), and Firewall communications.

Assembly Language

Slightly higher than machine language. Uses simple command words to supply step-by-step instructions for the processor to carry out. Assembly language directly manipulates the values contained in the microprocessor's registers. Uses hexadecimal codes, and although it is difficult to use, it creates compact, fast, code.

Die

Small block of semiconducting material, on which a given functional circuit is fabricated.

System Files

Small disk files that contain software code that are the first files a computer reads from disk when it is booted. The system files contain the information needed, following the initial hardware boot, to lead the rest of an operating system.

High-level Language

Software code written with recognizable words that more closely resemble conventional languages, such as English.

Source

The part of a transistor from which electrical current flows when the transistor is closed.

Burn-in

The process of exercising an integrated circuit at elevated voltage and temperature. This process accelerates failure normally seen as "infant mortality" in a chip. The resultant tested product is of high quality. (testing)

Boot or Boot-Up

The process that takes place when a PC is turned on and performs the routines necessary to get all the components functioning properly and the operating system loaded. The term comes form the concept of "lifting yourself by your bootstraps."

Flow

The sequence of functions a program follows.

Operating System

The software that serves a bridge between application software with which the computer user works.

Runtime

The time a program or routine is being executed. A program that is not dependent on an interpreter or other program the computer user works with.

How Windows

Windows uses virtual machines to allow each application 4GB of virtual RAM (actually hard drive space) to avoid applications having to compete with each other over resources. (Collisions among programs doing this in the past led to "Blue Screens of Death") The system virtual machines are in the processor's user mode, where human action can't crash it. Dangerous commands are stored in the kernel mode. When an application wants to call an O.S. service (write to a file), the application must go through the API (Application Programming Interface) API acts as a middle agent between the users, who could carelessly ask their applications to do something that could damage the kernel and its core services. Inside the Kernel of the O.S., is a set of services (code that powers the most common and most necessary functions of all Windows programs.) Applications can sue these services with little risk of treading on forbidden memory addresses.