Ch. 5 the system unit

Components

Personal computers come in a variety of different sizes, shape, and capabilities. Although they look different and each has its own unique features, they share surprisingly similar components, including system board, microprocessors, and memory.

ROM

Ready-only memory (ROM) chips have information stored in them by the manufacturer. Unlike RAM chips, ROM chips are not volatile and cannot be changed by the user. "Ready only" means that the CPU can read, or retrieve, data and programs written on the ROM chip. However, the computer cannot write-encode or change— the information or instruction in ROM.

System unit

The (system unit), also known as the (system chassis), is a container that houses most of the electronic components that make up a computer system

Graphic cards

Which provide high-quality 3D graphic and information for games and simulations.

Ports

A (port) is a socket for external devices to connect to the system unit. A cell phone typically uses a port to recharge its battery. Some ports connect directly to the system board, while others connect to cards that are inserted into slots on the system board. Some ports are standard features of most computer systems, and others are more specialized.

Tablets

Also know as (tablet computers), are very similar to cell phones, although tablets are large, heavier, and generally more powerful. Also, a tablet is not designed to be used as a phone and m, typically, cannot be connected to phone networks.

Laptops

(Laptops) have their system unit housed with selected secondary storage and input devices. Laptops, however, are large and more powerful. Their larger monitor is separate from the rest of the computer and attached to the system unit with a hinge. Unlike cell phones and tablets, most laptops do not accept input by touching the screen. Rather, laptops typically use an attachment keyboard and a mouse S the primary input devices.

Desktop

Are most powerful type of personal computer. Like cell phones and tablets, some desktop computers, like Apple's iMac, have their monitor and system unit housed together in the same case. These computers are known as (all-in-one desktops).

Smartphones

Are the most popular type of personal computer. They are effectively a thin slab that is almost all monitor, with the system unit, secondary storage, and all electronic components located behind the monitor. Designed to comfortably fit into the palm of one hand and accept finger touches on the monitor as the primary input, cell phones have become the indispensable handheld computer.

Cables

Are used to connect exterior devices to the system unit via the ports. One end of the cable is attachment to the device, and the other end has a connector that is attached to a matching connector on the port. Standard cables include USB, HDMI, Thunderbolt, and Ethernet.

Bus lines

As mentioned earlier, a (bus line)— also known simply as a bus— connects the part of the CPU to each other. Buses also link the CPU to various other components on the system board. A bus is a pathway for bits representing data and instructions.

Expansion card and slots— to meet the size constraint of cell phones, tablets, and laptops, fingernail-size expansion cards known as (SD cards) have been developed. These cards plug into expansion slots located within many cell phones, tablets, and laptops.

As previously mentioned, many personal computers allow users to expand their systems by providing (expansion slots) on the system board. Users can insert optioned devices known as (expansion cards) into these slots. Ports on the cards allow cables to be connected from the expansion cards to devices outside the system unit.

Character encoding

Assign a unique sequence of bits to each character. Historically, personal computers used the (ASCII (American standard code for information interchange) to represent characters, while mainframe computers used (EBCDIC (extended binary coded decimal interchange code). These schemes were quite effective; however, they are limited. ASCII, for example only uses 7 bits to represent each character, which means that only 128 total characters could be represented. This was fine for most characters in the English language but was not large enough to support other languages such as Chinese and Japanese. These languages have too many characters to be represented by the 7-bit ASCII code. The explosion of the Internet and subsequent globalization of computing have led to a new character encoding called (Unicode), which uses 16 bits.

Microprocessor chips

Chip processing capacities are often expressed in word sizes. A (word) is the number of bits (such as 32 or 64) that can be accessed at one time by the CPU. The more bits in a word, the more data a computer can process at the time. Eight bits group together to form a byte. A 32-bit-word computer can access 4 bytes at a time. A 64-bit-word computer can access 8 bytes at a time. Therefore, the computer designed to process 64-bit words has greater processing capacity. Other factors affect a computer's processing capacity, including how fast it can process data and instructions. The process speed of a microprocessor is typically represented by its (clock speed), which is related to the number of times the CPU can fetch and process data or instruction in a second.

Expansion Buses

Computer systems typically have a combination of different types of expansion buses. The principle types are USB, FireWire, and PCIe.

Careers in IT

Computer technicians repair and install computer components and systems. They may work on everything from personal computers and mainframe servers to printers. Some computer technicians are responsible for setting up and maintaining computer networks.

For multi core processors to be used effectively

Computers must understand how to divide tasks into parts that can be distributed across each core-an operation called (parallel processing).

(cache) (pronounced like cash) (memory)— improves processing by acting as temporary high-speed holding area between the memory and the CPU.

Even if your computer does not have enough RAM to hold a program, it might be able to run the program using (virtual memory). Most of today's operating systems support virtual memory. With virtual memory, large programs are divided into parts, and the parts are stored on a secondary device, usually a hard disk. Each part is then read into RAM only when needed. In this way, computer systems are able to run very large programs.

System board— is also known as the (mainframe) or (motherboard). The system board controls communications for the entire computer system. All devices and components connect to the system board, including external devices like keyboards and monitors and internal components like hard drives and microprocessors. The system board acts as a data path and traffic monitor, allowing the various components to communicate efficiently with one another.

For cell phones, tablets, and wearable computers, the system board is located behind the screen. For laptops and desktops, the system board is typically located at the bottom of the system unit or along one side. It is a flat circuit covered with a variety of different electronic components, including sockets, slots, and bus lines. • Sockets— provide a connection point for small specialized electronic parts called chips.

Specialty processors

In addition to microprocessor chips, a variety of more specialized processing chips have been developed and are widely used. For example, many cars have more than 100 separate specialty processors to control nearly everything from fuel efficiency to satellite entertainment and tracking systems.

RAM (Random Access Memory)— chips hold the program (sequence of instructions) and data that the CPU is presently processing.

It is also lost if there is a power failure or other disruption of the electronic current going to the computer. Secondary storage, which we shall describe in Ch. 7, does not lose its contents. It is permanent or nonvolatile storage, such as the data stored on a hard disk.

Memory

Memory is a holding area for data, instructions, and information. Like microprocessors, (memory) is contained on chips connected to the system board.

Numeric representation— This is the reason, then, that a two-state or binary system is used to represent data and instructions.

The decimal system that we are all familiar with has 10 digits (0,1,2,3,4,5,6,7,8,9). The (binary system), however, consist of only two digits—0 and 1. Each 0 or 1 is called a (bit)— short for binary digit. In the system unit, the 1 can be represented by a negative charge and the 0 by no electronic charge.

At one time, personal computers were limited by microprocessors that could support a single CPU that controlled operations.

These computers were limited to processing one program at a time. Now, many personal computers have (multi core processors) that can provide tow or more separate and independent CPUs.

Flash memory

This information is called the system's BIOS(basic input/output system). This information includes the specifics concerning the amount of RAM and the type of keyboard, mouse, and secondary storage device connected to the system unit. If changes are made to the computer system, these changes are reflected in the flash memory.

Microprocessor— in most computers systems, the(central processing unit(CPU)) or (processor) is contained on a single chip called the (microprocessor). The microprocessor is the "brain" of the computer system. It has two basic components: the control unit and the arithmetic-logic unit:

• Control unit— the (control unit) tells the rest of the computer system how to carry out a program's instructions. It directs the movement of electronic signal between memory, which temporarily holds data, instructions, and processed information, and the arithmetic-logic unit. It also directs these control signals between the CPU and input and output devices.

Wearable computers— also known as (wearable devices), are one of the first evolutionary steps to the Internet of Things (IoT). These devices contain an embedded computer on a chip that is typically much smaller and less powerful than a cell phone's. The most common wearable computers are smartwatches and activity trackers.

• Smartphones— like Apple's Watch. This device acts as a watch, fitness monitor, and communication device. For example, the Apple Watch connects to an iPhone to display e-mails, text messages, and calendar reminders on the user's wrist. • Activity trackers— like Fitbit's Flex 2. Thai device monitors daily exercise and sleep patterns. It also connects wirelessly to desktops, laptops, and smartphones to record and share data.

Power supply

• most cell phones and tablets are powered directly from batteries that are recharged using an (AC adapter). These adapters plug into standard wall outlets and convert AC to DC. With cell phones and tablets, a USB cable often connects the AC adapter to the mobile device. Some cell phones, however, can use a (wireless charging platform), eliminating the cable. Most tablets, mobile devices, and wearable computers can operate using battery power. Their AC adapters or charging platforms are only used to recharge batteries. • like cell phones and tablets, laptops typically use AC adapters that are located outside the system unit. Unlike cell phones and tablets, these computers can be operated either using an AC adapter plugged into a wall outlet or using battery power. Their batteries typically provide sufficient power for up to eight hours before they need to be recharged. • desktop computers have a (power supply unit) located within the system unit. This unit plugs into a standard wall outlet, converts AC to DC, and provides the power to drive all of the system unit components.

Specialized ports— in addition to standard ports, there are numerous specialty ports.

•Mini DisplayPort (miniDP or mDP) port— are audiovisual ports typically used to connect large monitors. These ports are used with many Apple Macintosh computers. •VGA (video graphic adapter) and DVI (digital video interface) ports— provide connections to analog and digital monitors, respectively. DVI has become the most commonly used standard, but VGA ports are still provided on almost all systems for compatibility with older/lower cost monitors. • FireWire ports— provide high-speed connections to specialized FireWire devices such as camcorders and storage devices.

Standard ports— most desktop and laptops computers come with a standard set of ports for connecting (peripheral), or external devices, such as a monitor and keyboard. The most common ports are:

•Universal serial bus(USB) ports— can be used to connect several devices to the system unit and are widely used to connect keyboards, mice, printers, storage devices, and a variety of specialty devices. There are many types of USB-B ports are found on peripheral devices, like digital cameras and cell phones. The newest USB type, (USB-C), is gaining popularity on cell phones and laptops. It is expected to replace USB-A and USB-B in the future. USB-C is faster, more powerful, and smaller than previous USB types. A single USB port can be used to connect many USB devices to the system unit. • High definition multimedia interface (HDMI) ports— provide high-definition video and audio, making it possible to use a computer as a video jukebox or an HD video recorder. • Thunderbolt ports— first introduced in Apple's MacBookPro computer, provide high-speed connections. A single port can connect up to seven separate devices connected one to another. Thunderbolt ports promise to replace a number of different types of ports, including Mini DisplayedPorts. • Ethernet ports— are a high-speed networking port that has become a standard for many of today's computers. Ethernet allows you to connect multiple computers for sharing files, or to a DSL or cable modern for high-speed Internet access.