Information Systems: Data Storage and Representation
Motherboard Components
- power connector to retrieve electrical power from a power supply - socket for installing the CPU, sometimes the CPU is soldered to the computer - slots for installing the main system memory - chipset that interfaces the CPU with main memory and peripheral buses - non-volatile memory chips, also known as Basic Input/Output System, contains a system of firmware needed to load OS from the hard disk - CMOS memory chip and its battery - clock generator to produce clock signal for synchronizing components - slots for expansion cards that provide access to the peripheral bus managed by the chipset - integrated controller for permanent storage devices and connectors that's typically a SATA bus driver - integrated controller for keyboard and mouse or serial or parallel port. All replaced by USB bus - one or several integrated USB bus controllers to connect external peripherals - heat sinks and mounting points for fans to dissipate excess heat Functions once provided with expansion cards are now integrated
CPU Operation
- prefetch unit extracts next instruction from memory then obtains necessary data, also from memory, putting them in CPU registers or the CPU internal memory - decode unit decodes to obtain operation - Arithmetic Logic Unit, ALU, performs the operation with data in CPU registers - next instruction is loaded from RAM sometimes, before loading a new instruction, a jump to another memory location is executed depending on the results of the previous instruction - control unit organizes this complete process synchronized by a central clock
8 Bits
1 Byte
1 Gigabyte, GB
1000 MB Needed to record symphony in High Fidelity PC memory measured in GBs
1 Kilobyte, KB
1000 bytes Storage needed for short story
1 Zetabyte, ZB
1000EB Expected internet traffic for 2016
1 Terabyte, TB
1000GB Complete collection of US Library of Congress needs 10TBs to be digitized
1 Megabyte, MB
1000KB Storage capacity for small novel
1 Exabyte, EB
1000PB If all US phone calls were stored for a year, 10EBs would be necessary
1 Petabyte, PB
1000TB Total information on the Internet measured in
1 Yottabyte, YB
1000ZB Number of snowflakes that fall on Earth each year
Motherboard
A Printed Circuit Board, PCB, that holds the main architectural components of a computer and provides electrical connections by which other components communicate Contains the CPU
Magnetic Disks
A RAM device meaning that information is indexed somehow and can be accessed independently of the rest by its position. Not to be confused with RAM memory in computer where random access is the opposite of sequential access. Floppy disks or diskettes and hard disks.
1 Bit
A binary decision; true or false, on or off
Computer Case
Also known as a chassis, tower, system unit, cabinet, base unit, or a case Contains most of the components of a computer and comes in many sizes or form factors An ATX motherboard and PSU may take form of a vertical tower, flat desktop, pizza box with desktop, or mini tower case, popular in business environments
ASCII Text Representation
American Standard Code for Information Interchange provides the most used translation table from text to binary. Originally developed for telegraph communication, uses 7-bits or 128 characters 1 bit difference between small and capital letters
Memory Cards
Based on flash memory, storage device sealed in a plastic cartridge. Absent of a unique standard, but SD, Secure Digital format, tends to win. Used in digital cameras and expansion in portable electronic devices like tablets, smart phones, ebooks, and video game consoles. Transfer speed is an important consideration in HD video recording or high end cameras.
Hyperthreading
Can be combined with CPU cores to allow the execution of two different threads of the same program almost in parallel A single processor can execute 8 instructions in parallel
Image Data Type
Captured with resolution in pixels where values stored for each pixel are usually the amount of red, green, and blue it contains Color depth - can store different numbers of colors per pixel depending on number of bits used Can be compressed to eliminate spatial redundancies where similar zones can be stored using less bits
CPU
Central Processing Unit Computer component that executes program instructions stored in computer memory CPUs manufactured in silicon wafers, each one with 500 to 1000 processors A modern CPU has more than 2 billion transistors and, with miniaturization, will increase The processors are developed with 14 nanometer technology, 10 times smaller than a virus
Optical Media Lands
Characterisitc of reflective material of optical media identified as the area between two pits where a change between a pit and land represents a 1 and no change represents a 0
Optical Media Pits
Characterisitc of reflective material of optical media identified by dents over the surface.
Sequential Access
Characteristic of magnetic media where information must be accessed with order from beginning; making it difficult to insert a value in the middle.
CMOS
Complementary Metal Oxide Semiconductor A low-power memory, powered by a battery, that keeps some information about basic hardware settings like date and time
Expansion Slots
Connectors for expansion cards like sound cards, network cards, or graphics cards First featured ISA technology then evolved into PCI then PCIexpress or PCIe In modern computers there are PCIe slots with higher bandwidth for external graphics cards
Ports
Connectors on the computer case for external devices Screen ports: VGA, DVI, HDMI Sound ports: headphones, speakers, microphones General purpose ports: use USB to connect hard disks, printers, scanners, mouse, keyboard Network ports: gigabit Ethernet network interface adapters or bays for flash memory cards Older computers have serial ports, a parallel port for printers, mouse and keyboard ports, and a modem port
Signal Sampling
Conversion from analog to binary involves discarding part of the information by selecting values at some given points to get a discrete signal. The combination of these values is a sample where the number taken per second depends on the highest frequency of the signal. More points are needed to represent fast changing signals.
DVD
Created for recording video due to CD capacity limitations. Formed by two layers of reflective material, doubling capacity. 4.7 gigabyte capacity or around 9 for double-sided disk.
CD-R
Created to be recorded once and read many times.
Data Recording or Burning
Creates pits over optical media surface using a laser beam
Boolean
Data type that provides a straightforward representation of true or false where each piece of data only needs 1 bit
Number Data Type
Data type with straightforward codification depending on range of numbers used and only need enough bytes to represent in binary the maximum integer used Negative numbers need one more bit to encode Are real numbers Defined in IEEE standard 754 3 components 1.) a bit for the sign 2.) 8 bits for exponent in base 2 3.) 23 bits for mantissa to represent decimal values Precision = 32 bits Double Precision = 64 bits Quadruple Precision = 128 bits
Disk Sector
Defined by the intersection of a track and a sector. When a file is stored in a disk, it is divided into a set of disk sectors, a minimum unit that can vary from 512 bytes to 4 kilobytes. Modern disks store information in contiguous groups of sectors called clusters. To reuse disk space left when a file is erased, files are divided into clusters for storage so part of a file can be put in the space left by a smaller erased file then the rest stored in other free space of disk. However, fragmentation increases accessing time resulting in lower performance.
Disk Boot Sector and Partition
Disks can be configured to hold several partitions. Disks contain a boot sector that allows the computer to load OS from them in the boot up process. IBM PC cpmpatible systems have a MBR, Master Boot Record, in the disk that identifies master partition and volume boot record in each partition to load OS from if it is in active position. This allows for several OS to be installed and chosen from.
DDR
Dual Data Rate Most recent version is DDR-4 Used by DIMM to exhchange data twice per a DRAM clock cycle
DIMM
Dual-in-Line Memory Module Has several slots to be added in the motherboard with a capacity of 1 to 16 gigabytes
DRAM
Dynamic Random Access Memory, RAM, Type of memory slot packed in memory modules called DIMM
CPU Internal Clock
Each CPU instruction needs a specific number of clock cycles to be executed Word length: the number of bits a CPU can receive when assessing memory where more bits means better performance Cores: the number of cores in a processor affects the amount of instructions that can be executed at a time. Modern computers have 4 to 6 processors
Solid State Storage Device or Flash Storage
Electronic permanent storage without moving parts. Named for several different technologies, but most devices in the market are based in nonvolatile, NAND-based flash memory able to retain data without power. Read and written in blocks and had a max number of rewrite cycles.
EBCDIC
Extended Binary Coded Decimal Interchange Code Created by IBM for punched cards used to program early computers. Now used in IBM System/360 mainframes. Letters were represented in 3 blocks: A-I, J-R, S-Z Numbers used the same criteria as ASCII, but with different codification
Third Extended File System
File allocation system for disk formatting common to Linux
Hierarchical File System Plus
File allocation system for disk formatting common to MacOS
Page Files or Swap Files
Files where RAM content is stored in the hard disk
Cache Memory
First level in the computer memory hierarchy after CPU register Inexpensive mechanism that allows for faster access to program instructions and uses an algorithm to select most the used data in order to store copies Modern computer processors integrate into the CPU chip with independent caches for instructions and data Data cache is organized in L1, L2, L3... depending on speed
Magnetic Tape
First magnetic media used by a computer with a large caacity of more than 100 terabyte and low cost per unit of storage
Computer Architecture
Goal: transform input data into output information through instructions of program - input device retrieves data from a user or environment and introduces it to the system - CPU executes program instructions fetching data, making operations, and returning the results to memory - memory stores the resulting data in addition to the program instructions controlling computer - output device sends the obtained results to user Permanent storage, considered an input and output device, keeps programs for future execution and data for future queries
Moore's Law
Gordon Moore, co-founder of Intel, predicted in 1965 that the number of components in an internal heated circuit would double every 18 months Studies suggest the end of this law will come in 20 years
Hexadecimal Representation
Has direct translation with binary if grouped in a 4-bit combo 48 bits = 6 bytes = 6 groups of 2 hexadecimal numbers acting as an identifier for network controllers Used for long chains of bits such as a MAC address of a network interface card, formed by 48 bits Representation of colors in RGB use 2 hexadecimal figures for each of the three components
File Allocation Table 32, FAT32
IBM PC compatible form of disk formatting used in USB pens and floppy disks. Has capacity limitation of 4GB
Quantization Error
In the discrete to digital conversion of a signal, the difference between the input and resulting quantized value is referred to as the quantization error, a round off error.
Address Bus
Indicates which device is being accessed
NTF
Microsoft compatible form of disk formatting that solves capacity limitations of FAT32, but has difficulty being recognized by other OS, especially for writing operations.
Von Neumann Architecture
Modern computer architecture where main memory temporarily stores program data and instructions All computer components are connected through the system bus formed by the data bus, address bus, and control bus.
ATX PSU Standard
Most computers conform to specifications that include form factor and voltage tolerance with supplies of +3.3V, +5V, +12V, and -12V While the ATX PSU is connected to main power supply, it always provides a 5V standby voltage, 5VSB, to power standby functions and peripherals Power supply can be enabled and disabled by a signal from the motherboard
Form Factor
Motherboard specifications including dimension, power supply type, location of mounting holes, number of ports on back panel, etc.
Text Data Type
Must apply a translation table or character set that provides binary code for each character Same values for first 128 consisting of alphabet letters and digits, but will have problems with local characters like symbols
Discrete to Digital Conversion
Once a discrete number of values is obtained, each value can be any real number, infinite possibilities. Information is again reduced by quantizing the discrete signal. The resulting digital signal can only be a value from a predetermined set of possibilities; reducing storage needs. If a byte is used to represent each sample, it will have to be stored as ones if 256 different values. For more precision, must use a larger number of possible values: storing more bits per sample.
1 Byte
One character
Blu-ray, BD
One of the first HD optical disks with same physical size as CD or DVD. A blue laser beam is used to read disk. Can store 25 gigabytes per layer
Chipset
One or several integrated circuits hat manage an interface between the CPU, main memory, and peripherals Once made of North bridge and South bridge chips North bridge: links the CPU to high-speed devices like RAM and graphic controllers. Connects directly to the CPU using Front Side Bus, FSB South bridge: connects lower speed peripheral buses as hard disk and USB buses Connects to the North bridge In modern chipsets, the North bridge is integrated into a processor chip and the South bridge contains on-chip integrated peripherals like Ethernet, USB, and audio
CD-ROM
Originally created to store and play sound, but were adapted to store all types of data. Once read-only media with capacity of 74 minutes of music or 650 megabytes of information.
Disk Bay
Places reserved for storage devices like hard disks, CD, or DVD units called bays Number of disk bays depends on size of computer case
PSU
Power Supply Unit Converts main Alternating Current, AC, from electrical outlet to a continuous, regulated Direct Current, DC, used to power internal computer components Modern computers will use a switched mode power supply, with a manual selector for input voltage or voltage adaptability
Analog to Digital Conversion
Process done in real time by AID converters. To get back analog version, must use a DIA converter; however, product won't be the same as original due to information loss. Both converters are devices usually integrated into some peripheral like a sound card.
Hard Disk
RAM magnetic disk once nonremoveable locked in a computer bay inside the main unit. Now external hard disks can be plugged in and unplugged without need for reboot.
RAM
Random Access Memory The main memory of a computer According to the Von Neumann architecture, RAM temporarily stores instructions of programs in execution and the data they use Access time to a memory location is independent of desired address. Information retrieval time is the same from any random access Volatile memory where stored information is lost if the computer turns off
Solid State Drive, SSD
Random access device, but drive defragmentation not necessary and not recommended with a max number of write cycles. Boosts speed in reading operations with no moving parts.
ROM
Read-Only Memory Memory recorded by the computer manufacturer that can only be read, never erased Plays a role in the booting up process of a computer ROM programs are the first to be executed, checking components and loading the OS
Floppy Disk or Diskette
Removeable RAM magnetic disk composed of a thin, flexible layer of a magnetic material sealed in a plastic carrier. Size and capacity has evolved from 8 inch disks to final format of 3.5 inches and barely 1.5 megabytes. Replaced entirely with USB flash memory, external hard disks, and cloud storage.
Disk Defragmentation
Reorganizes fragmented disk sectors or clusters to increase performance
Binary Digit or Bit
Representation of information in a computer can be 1 or 0 where a sequence of bits can represent any type of data.
Octal Representation
Represents file permissions in Unix where there are read, write, and execution permissions codified by an octal number. Uses 8 digits that have direct translation to binary if grouped in a 3-bit combo
CD-RW
Rewriteable disk that can be recorded and erased 1000 times
Video Data Type
Sequence of images captured fast enough for human eye to notice Can be compressed to eliminate spatial and temporal redundancies
Analog Signal
Signal with value that varies continuously with time where the value in a given moment can be any real number Most quantities in the real world can be represented by an analog signal Sound, temperature, barometric pressure, light levels, wind strength
CPU Performance
Speed: measured in Hertz or cycles per second, not technically a measure of speed but frequency of the internal clock, where more Hz means more processing speed Temperature: temperature in the CPU rises with high frequency and, with miniaturization, heat dissipation becomes harder
USB
Standard for connecting many kinds of devices 3.1 is the current specification that supports a high bandwidth capacity A thunderbolt high speed general purpose port is found in Apple computers
Optical Media
Storage media that uses properties of light to store information on material with reflective capabilities so there is no physical change, instead depressions to indicate 1 or 0.
Sound Type
Stored in sequence of binary called sample values where time separation of samples depend of the maximum frequency of recorded sound Higher frequency = more samples Precision depends on number of bits used to store data type Can be compressed to eliminate temporal redundancies
Memory Pagination
The OS organizes memory for different applications in pages that can be moved between RAM and the hard disk
Disk Formatting
The internal structure of disks, hard disks,diskettes, CDs, DVDs, is defined by a formatting process consisting of two types of blocks: tracks, concentric rings, and sectors, circular sectors.
Magnetic Media
The most common permanent storage devices use magnetic material to store information where their surface is covered by small particles whose orienation determines a 1 or 0 value to store. Because of sequential access, most useful for backup support or definitive storage for information that is written oncce and read many times
Control Bus
Transports status signals between different devices
Unicode and UTF-8
Universal binary representation that is language independent codification with enough space to represent any language character in the world. Uniform using fixed codification length UTF-8 is widely spread in web browsers and allows for the combination of characters from different languages in the same page Numbers are 1 to 4 bytes ASCII characters 1 byte Romance languages Greek, Arabic, Cyrillic 2 bytes Chinese, Japanese, Korean 3 bytes Supplemental characters 4 bytes
File Allocation Table
Used to locate first cluster where each cluster has inforamtion regarding next assigned to file. When a file is erased, the address is removed from table and clusters are marked as free, but information is not erased until another file is saved to that cluster. File recover programs look for chains of unused clusters to see if they contain complete, erased files.
IBM Personal Computers
Uses a standard form factor to ensure interchangeability of parts Most commonly Advanced Technology Extended, ATX,
USB Flash Drive or Pen Drive
Uses flash memory and integrated USB connection to plug in to computer. Replaced diskettes and CDs as removable media. Variance in capacity from 8 and 128GBs up to 1TB.
Binary Coding
When converting signals, you only need enough bits to represent all possible states of a sample. The number of bits used to store each sample is called bit depth
Virtual Memory
When there is not enough RAM left, the OS uses virtual memory to set aside a portion of storage on a hard disk to act as additional RAM
The Binary System
Where 3 bits represent 2^3=8 possibilities from 000 to 111
Data Bus
Where data is exchanged by internal computer components like the CPU, memory, and input and output devices
