Many of the components found in computers today are basically the same components you'd find in almost every major household appliance. Most of these components have been used since the late 1960s. For example, every television set contains resistors and transistors. Automobiles today actually contain small computers that monitor the speed of the car and make adjustments to the fuel mixtures accordingly.
Analog vs. Digital
Before we discuss electronic components we must define the words analog and digital because we will be using them throughout our discussions of computer technology.
Today's computer components use digital signals, which are signals that contain values that are discrete. Analog signals, on the other hand, change values over time. Consider the different between two common types of light switches: a standard light switch and a dimmer switch. The standard light switch has only two values: on and off. As a rule, at any one time the switch will be in either one position or the other. This is similar to digital electrical signals, which have discrete values (like on and off). By way of comparison, the dimmer switch starts at off, but can be changed gradually to stronger and stronger intensities, up to the full on setting. At any one instant, a dimmer switch can have a setting almost anywhere between on and off. This is similar to an analog electrical signals, which may be on or off or somewhere in between.
Vacuum Tube--The Old Days....
Today's computer components are the products of previous generations of trail and error. Each generation improves upon the previous ear. The grandfather of today's computer components is the vacuum tube (Figure 1.1).
FIGURE 1.1. A Vacuum Tube
The vacuum tube is really nothing more than a switch. A small voltage at one pole switches a larger voltage at the other poles on or off. Because information in a computer is represented as binary (1s and 0s), switches are ideal--because they too have only two positions, 1 or 0.
The first electronic computers contained cabinets full of vacuum tubes. There were several problems with this. First, the tubes utilized a heating element in order to facilitate the flow of electrons between the poles. These heating elements had to be "warmed up" in order to function properly. Thus, it took several minutes to turn the computer on. Also, with several tubes in the same cabinet, the elements would generate quite a bit of heat. Unfortunately, heat shortens the life of electronic components--so each computer usually had a room full of air conditioning equipment just for keeping the tubes cool! Even so, the average temperature in these computers was greater than 100 degrees Fahrenheit.
Second, the vacuum tubes were very bulky. Computers like the first computer, ENIAC, often took up enough cabinets to fill an entire floor of a building, with the computer in one room and the air conditioning equipment in the one next to it.
Transistors--Turn Them On
If the vacuum tube is the grandfather, then the transistors is the parent of today's electronic components. Transistors (Figure 1.2) work in basically the same manner as vacuum tubes. A small voltage applied to one pole controls a larger voltage on the other poles. The difference between a transistor and a vacuum tube is that a transistor uses a sandwich of silicon instead of tube filled with gas to do the switching. Silicon falls into a family of elements that are neither conductor nor insulator; they're called semiconductors. This type of element will be either a conductor or an insulator depending on some condition. In the case of transistors, an electrical current will cause the silicon to be a conductor.
FIGURE 1.2 A transistor
Transistors overcame most of the limitations of vacuum tubes. They generate very little, and they are much smaller than vacuum tubes. With transistors, computers that fit into a single room could be made. As manufacturing techniques have become more precise, transistors have gotten smaller and smaller. Today, five million transistors can fit into an area smaller than a thumbnail.
Resistors--Keeping Electricity at Bay
Another component that is commonly used in computers is the resistors. As its name suggests, it resists the flow of electricity is dissipated in the form of heat. There are two types of resistors: fixed and variable.
Fixed Resistors
Fixed resistors used when you need to reduce the current by a certain amount. They are easily identified by their size and shape (see Figure 1.3). Their resistance level is indicated by means of colored bands painted on the resistor.
FIGURE 1.3 A fixed resistor
Analog vs. Digital
Before we discuss electronic components we must define the words analog and digital because we will be using them throughout our discussions of computer technology.
Today's computer components use digital signals, which are signals that contain values that are discrete. Analog signals, on the other hand, change values over time. Consider the different between two common types of light switches: a standard light switch and a dimmer switch. The standard light switch has only two values: on and off. As a rule, at any one time the switch will be in either one position or the other. This is similar to digital electrical signals, which have discrete values (like on and off). By way of comparison, the dimmer switch starts at off, but can be changed gradually to stronger and stronger intensities, up to the full on setting. At any one instant, a dimmer switch can have a setting almost anywhere between on and off. This is similar to an analog electrical signals, which may be on or off or somewhere in between.
Vacuum Tube--The Old Days....
Today's computer components are the products of previous generations of trail and error. Each generation improves upon the previous ear. The grandfather of today's computer components is the vacuum tube (Figure 1.1).
FIGURE 1.1. A Vacuum Tube
The first electronic computers contained cabinets full of vacuum tubes. There were several problems with this. First, the tubes utilized a heating element in order to facilitate the flow of electrons between the poles. These heating elements had to be "warmed up" in order to function properly. Thus, it took several minutes to turn the computer on. Also, with several tubes in the same cabinet, the elements would generate quite a bit of heat. Unfortunately, heat shortens the life of electronic components--so each computer usually had a room full of air conditioning equipment just for keeping the tubes cool! Even so, the average temperature in these computers was greater than 100 degrees Fahrenheit.
Second, the vacuum tubes were very bulky. Computers like the first computer, ENIAC, often took up enough cabinets to fill an entire floor of a building, with the computer in one room and the air conditioning equipment in the one next to it.
Transistors--Turn Them On
If the vacuum tube is the grandfather, then the transistors is the parent of today's electronic components. Transistors (Figure 1.2) work in basically the same manner as vacuum tubes. A small voltage applied to one pole controls a larger voltage on the other poles. The difference between a transistor and a vacuum tube is that a transistor uses a sandwich of silicon instead of tube filled with gas to do the switching. Silicon falls into a family of elements that are neither conductor nor insulator; they're called semiconductors. This type of element will be either a conductor or an insulator depending on some condition. In the case of transistors, an electrical current will cause the silicon to be a conductor.
FIGURE 1.2 A transistor
Transistors overcame most of the limitations of vacuum tubes. They generate very little, and they are much smaller than vacuum tubes. With transistors, computers that fit into a single room could be made. As manufacturing techniques have become more precise, transistors have gotten smaller and smaller. Today, five million transistors can fit into an area smaller than a thumbnail.
Resistors--Keeping Electricity at Bay
Another component that is commonly used in computers is the resistors. As its name suggests, it resists the flow of electricity is dissipated in the form of heat. There are two types of resistors: fixed and variable.
Fixed Resistors
Fixed resistors used when you need to reduce the current by a certain amount. They are easily identified by their size and shape (see Figure 1.3). Their resistance level is indicated by means of colored bands painted on the resistor.
FIGURE 1.3 A fixed resistor
Integrated Circuits (ICs)--Welcome to the 1980s
With today's manufacturing techniques, it is possible to put all of these components together into circuits that perform certain functions. In the 1970s' you might have hooked up several components on boards called circuit boards. Starting in the 80s, components were etched into pieces of silicon no larger than a dime. In order to get this small onto a circuit board, the silicon wafer is placed into a package that has pin coming out of it. These pins are wired with tiny copper or gold wiring directly to the silicon chip. This package comes in several forms, but is generally called an integrated circuit chip or IC chip.
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