Introduction to Computing- Hardware

Mouse

Unless you've been living under a rock, you already know what a mouse is. Just know that it's an input peripheral and allows the user to move the pointer on a GUI (Graphical User Interface).

L1 cache

This is the first level of cache for the CPU, and is generally very small. In modern processors, a typical level 1 cache is 64 kB. This is the fastest level of cache, and the processor checks this first.

Fetch

This step fetches the next instruction from the memory at an address stored in the program counter

Non-Volatile Memory

This type of memory doesn't need power to hold onto the data that it's storing. Even if the power is turned off (or lost), non-volatile memory will still retain its information for the next time it's needed. Desktop computers today have ROM (Read Only Memory) a form of non-volatile memory which then accesses the operating system upon startup. Most non-volatile memory uses circuits or magnetism to hold data after electricity is removed, but non-volatile phase change memory uses chalcogenide glass to hold data, and is much faster than magnetic memory such as hard drives, or even circuit based memory like flash drives.

Bit

- A bit is the basic unit of computing information. You can think of it as the smallest part of memory there is. It can only have two possible states (on, off) (+, -) (true, false) (1,0). While that may not seem like much, it is the basis for everything that happens in computers today. A bit by itself isn't much use to us, but if you string enough of them together, they can create more identifiable things. For example, 01001010 is eight bits that equal the capital letter "J". When we have eight bits together, we call that a byte. 8 bits = 1 byte

Pipeline

- A computing pipeline is a 'series' or analogically, a pipe of processes or data, where the output of one unit is the input in the following unit. Data is handed from one part of the processor to the other in order to be fully processed. Processors use pipelines in order to carry out instructions.

Monitor

- A monitor is an output device that is used to display data or images to the user. The first monitors developed were cathode ray tube (CRT) monitors, similar to that of a television. Today, most monitors are thin film transistor TFT panels, lit by either LCD (liquid crystal display) or LED (light emitting diode) backlights.

Printer

- A printer is an output device which is able to print characters onto a sheet of paper for a user to read. The two primary types of printers are inkjet printers and laser printers. Inkjet printers use an ink-writing head to write letters onto paper, whereas laser printers use electric corona discharge to place and fuse toner (which is basically dry powder) onto the paper. Just remember, ink-jet = wet ink, and laser = dry toner.

Scanner

- A scanner optically reads (scans) a page and converts it into a digital image file (.jpg, .png, etc). Common scanners include flatbed scanners, on which a piece of paper is placed flat onto the glass, and the image is 'read' by a charge coupled device (CCD).

Serial/Parallel Processing

- A serial process is one that occurs in series, where one process needs to be finished before the next can be begin. A parallel process is a process that can be run at the same time as another. The human brain is a classic example of a system which has multiple parallel processes ongoing. Until recently, the majority of computer processes were serial in nature. With the development of multi- core and multi-thread processors, personal computers are now capable of parallel processing.

Motherboard

- Also called a system board, the motherboard is the primary circuit board found in computers. You can think of this as the table upon which all other parts of the hardware sits on. The CPU, the system cache, the graphics cards, USB connections and NICs, all sit on the motherboard. Some of these things are attached directly to the motherboard, like the USB connections and system cache. Others are plugged into the motherboard via expansion ports.

Compact Disc (CD)

- Compact discs are a form of physical media which were developed in the early 1980's by Phillips and Sony. They can hold between 500 to 700 megabytes of data. CD's store data through written pits on the surface of the polycarbonate layer, which is read by a 780 nm laser.

Keyboard

- Ditto for the keyboard as well. Just know that it is an input peripheral device, and that many have number keypads.

Execute

- During execution, the CPU performs the action told by the decoded instruction. This could include reading values from existing registers, passing them to the logic unit to perform a logical/mathematical function, or writing to a register.

Expansion Ports

- Expansion ports or slots are areas of the computer motherboard in which additional hardware components can be placed to increase the capability of the computer. A list of common expansion ports is given below:

Pixel/Resolution

- Pixels refer to the number of distinct, points of light in a display device like a monitor screen. The term comes from a shortening of the term 'picture element'. The number of pixels in a display determines the resolution. A standard monitor today will have a typical resolution of 1024 x 768 pixels, which roughly refers to the number of pixels in the X and Y directions respectively. 1024 multiplied by 768 gives us a total resolution of 768,432 pixels. For the exam, I'd know that the resolution defines how many pixels are on the screen, and therefore how sharp/detailed the image will be.

Random Access Memory (RAM)

- Random access memory can be accessed at any point or area in the memory. In other words, unlike a hard drive or other memory using SAM, it doesn't need to wait for a full rotation of the platter or tape, but can jump directly to where the data it needs is located. Thus, the time required to access data is significantly reduced compared to sequential access memory. This is the type of memory that computers use for its cache and for general system memory. It is usually made up of volatile memory, so it cannot hold information for long.

L2 cache

- The L2 cache is the intermediate cache, and holds between 128 kB to 256 kB of memory. It is also known as the secondary cache.

L3 cache

- The L3 cache is the largest, and determines to a significant extent the speed of memory access a CPU between 3-6 MB of level 3 cache.

Virtual Memory

- Virtual memory is basically a CPU using sleight-of-hand. It does this to fool an application into thinking that the available RAM is much higher than it actually is. For example, if I only have 20 megs of RAM, but I have three applications that all require 10 megs each; this would normally cause an "Out of Memory" error. However, with virtual memory the CPU would assign each application 10 megs of virtualmemory. It does this by filling up the 20 megs of RAM we do have with the parts of the applications we'll use most often. Then it takes the rest and copies it to the computer's hard drive. If one of the applications needs something copied on the hard drive, the CPU knows just where to go find it. Of course, the speed to access something in RAM and the hard drive is very different, and virtual memory is almost always slower than having everything in RAM. However, as our example shows, it does allow us to run more than the computer normally would be able to.

Modem

-A modem is a peripheral device that allows your computer to connect to other computers and the internet. It does this by converting the signal from your computer and then passing it over a cable line, telephone wire, or wireless connection.It then takes the signal back from the connection and converts it back into digital signals that your computer will understand. Modems come in many shapes, from Cable Modems, DSL Modems, Wireless Modems, and even the old dial-up modems.

Memory Sizes

A byte is also what we use to measure memory sizes. The most common memory sizes you'll hear today are kilobyte, megabyte, gigabyte, and terabyte. As you can probably tell, we use metric standards for describing how many bytes there are. But remember that computers work in binary or base 2 (on, off) (1,0) so memory size always doubles - 1, 2, 4, 8, 16, 32, 64, 128, 256, etc, etc, etc. That's why we have 512 megabytes of memory instead of 500.

Fax (Telefax)

A fax machine, also known as a telefax or telecopy machine, can transmit scanned printed material over a telephone wire to a remote printer or other computer. More recently, fax machines have become less utilized due to internet options (scanners, e-mail and cloud), but are still useful for obtaining signatures, etc.

Peripheral Devices

A peripheral device is a device which is connected to a computer but not part of the computer itself. This could include the mouse, monitor, keyboard, or speaker. Just remember that it is not a core part of the computer. An easy way for most people to remember - If it has to be plugged into the computer, then it's a peripheral.

Network Interface Card (NIC)

Also known as the network interface controller or LAN adapter, the NIC is a hardware component that connects a computer to a network or modem. NICs usually do this with a RJ-45 computer cable (commonly referred to as an Ethernet cable). Today, NICs are integrated directly into the motherboard of most personal computers, but do serve the same purpose as the hardware card. Network interface cards are necessary for physical connections to other computers or the internet.

Instruction Cycle

An instruction cycle is a set of predetermined steps that the CPU takes in order to grab instructions from a program, decode the instructions, and then execute those instructions. Because of this, the instruction cycle is also known as the FDX cycle, for Fetch, Decode, and Execute. Each of the steps is described below:

System Cache

Cache is a temporary storage memory which usually has a very fast access time. Data that is intended for immediate use will be stored in the cache, so that it will be ready as soon as it's needed. When the CPU needs to read from or write to a location in main memory, it first checks whether a copy of that data is in the cache. If it is not available, then pulling the data from the main memory will be much slower.

Refresh Rate

Even when we have a non-changing image on the screen, the computer is constantly refreshing the picture too fast for us to notice. The refresh rate is the rate at which new data is refreshed/renewed onto the display. A normal display typically has a refresh rate of 60 Hertz (abbrev. Hz), meaning each second the display is refreshed 60 times.

Flash Memory

Flash memory is a form of permanent data storage. Flash memory uses electricity instead of magnetism to store information, but unlike volatile memory, it keeps the data even after the power is removed. For the DSST, don't worry about the technical aspects too much. Just know that this type of memory is common in phones, USB flash drives, and more recently in solid state drives for personal computers.

Data Storage/Hard Drives

Hard drives are used for storing permanent data. The majority of hard drives operate using large metallic platters which are magnetic. The magnetic surface of the platter is divided into nanometer sized regions which are used to store individual units (bits) of information. The data is recorded through magnetization of these regions. The platters are constantly spinning like a record on a record player, and just like a record player, an arm reads the magnetic fields to read and write data to the platter. Most hard drive platters spin up to 5400 times a minute! That's pretty fast, but it's still slower than RAM since the arm needs to wait until the platter spins to the correct location.

Hardware

Hardware is described as the physical parts of a computer, and include parts such as the CPU, motherboard, graphics/audio cards, memory (RAM), and hard disks. It also includes any components of those parts. Basically, hardware is any physical component of the computer.

Hertz

Hertz is a standard unit, and in computing is measured by how many operations (instructions) a CPU can complete in one second. A computer with 1 megahertz of processing power can perform one million operations per second. That may sound like a lot, but it would horribly slow by today's standards. Most desktop computers today operate between 2-3 gigahertz, which can be up to 3 billion operations per second!

Input Device/Output Device

Input and output devices are used by people to communicate with a computer, and for the computer to communicate with people. Input devices include scanners, keyboards and mice. Output devices include monitors, printers, and speakers. Keep in mind that it is possible for a peripheral to be both input and output, such as a fax machine.

Metric Conversions

Much of computer terminology is based on the metric conversion system. However, it should be noted that that computers operate on a binary (base 2) system, meaning that a megabyte (Ideally 1,000,000 bytes) is actually 1,048,576 bytes. The metric prefixes are shown below, and I would know them all the way from nano to peta for the DSST:peta- 1015 1 quadrillion tera- 1012=1 trillion giga- 109=1 billion mega- 106=1 million kilo- 103=1 thousand deci- (d-) 10-1=1 tenth centi- (c-) 10-2=1 hundredth milli- (m-) 10-3=1 thousandth micro- (μ-) 10-6=1 millionth nano- (n-) 10-9=1 billionth

PCI Express

PCI express (Peripheral Component Interconnect Express) is a common expansion slot typically used for graphics cards and physics cards. PCIe was first introduced in 2003. (This may be a bit current for the DSST exam, but I wanted to include it just in case)

Universal Serial Bus (USB)

People tend to think of this as a connection type, but it's actually a standard. Companies like Compaq, DEC, Microsoft, IBM, Intel, and Nortel all got together to agree on a type of connection for keyboards, mice, and other peripherals. Otherwise, we may have fifty types of connections for keyboards today, just like we used to have for cell phones. ;) USB is one of the most common connection devices used today, and the current version, USB 3.0 is able to transfer data at a rate of 5.0 Gbits/sec.

Sequential Access Memory (SAM)

Sequential access memory is memory that must be accessed in sequence (i.e. the first part of the memory must be read before moving onto the second part). It's slower, but many types of memory using SAM holds onto the data even if there's no power. This sort of storage is seen in CD's, DVD's, magnetic hard disk drives, and floppy disks.

AGP

Short for Accelerated Graphics Port, this slot was used to attach a graphics card to the motherboard. AGP was introduced in 1997 by Intel, and phased out in 2004 after the introduction of PCI Express.

ISA

Stands for "Industry Standard Architecture" and is by far the eldest of the expansion slots. It's hard to find a motherboard with ISA slots today.

PCI

Stands for Peripheral Component Interconnect (how's that for a name?) and replaced ISA slots early on. This was the most common type of slot until the advent of PCI express. Sound cards, NICs, and even graphics cards went here until the arrival of the AGP slot.

Central Processing Unit (CPU)

The central processing unit of a computer is the part that performs the input/output, arithmetic, and other logical operations inside a computer. You can think of it as the "brain" of the computer. Without a CPU, none of the other parts of the computer would know what to do. The CPU directs all the other parts by use of an instruction cycle.

Decode

The decoder interprets the instruction

Volatile Memory

Volatile memory is memory which is only maintained for as long as the computer is on and providing power. After shutdown, the memory is lost. Most types of RAM (SD RAM, DDR RAM) are volatile memory. Just remember, nothing is held in volatile memory if there's no power. Once the power goes, so does whatever information is in the memory.