In mathematics and computing, hexadecimal (also base 16, or hex) is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F (or alternatively a–f)
to represent values ten to fifteen. Hexadecimal numerals are widely
used by computer systems designers and programmers. In computing,
hexadecimal numerals are usually written with a prefix, "0x" (in
reference to the abbreviated pronunciation of "hexadecimal").
Alternately, some authors denote hexadecimal values using a suffix or
subscript. For example, one could write 0x2AF3 or 2AF316, depending on the choice of notation.
As an example, the hexadecimal number 2AF316 can be converted to an equivalent decimal representation. Observe that 2AF316 is equal to a sum of (200016 + A0016 + F016 + 316), by decomposing the numeral into a series of place value terms. Converting each term to decimal, one can further write: (216 × 163) + (A16 × 162) + (F16 × 161) + (316 × 160),
(2 × 4096) + (10 × 256) + (15 × 16) + (3 × 1), or 10995.
Each hexadecimal digit represents four binary digits (bits), and the primary use of hexadecimal notation is a human-friendly representation of binary-coded values in computing and digital electronics. One hexadecimal digit represents a nibble, which is half of an octet or byte (8 bits). For example, byte
values can range from 0 to 255 (decimal), but may be more conveniently
represented as two hexadecimal digits in the range 00 to FF. Hexadecimal
is also commonly used to represent computer memory addresses.
Sabado, Setyembre 27, 2014
Octal number
The octal numeral system, or oct for short, is the base-8 number system, and uses the digits 0 to 7. Octal numerals can be made from binary
numerals by grouping consecutive binary digits into groups of three
(starting from the right). For example, the binary representation for
decimal 74 is 1001010, which can be grouped into (00)1 001 010 – so the
octal representation is 112.
In the decimal system each decimal place is a power of ten. For example:
In the decimal system each decimal place is a power of ten. For example:
Binary number
In mathematics and digital electronics, a binary number is a number expressed in the binary numeral system, or base-2 numeral system, which represents numeric values using two different symbols: typically 0 (zero) and 1 (one). More specifically, the usual base-2 system is a positional notation with a radix of 2. Because of its straightforward implementation in digital electronic circuitry using logic gates, the binary system is used internally by almost all modern computers and computer-based devices such as mobile phones. Each digit is referred to as a bit.
Biyernes, Setyembre 19, 2014
OTHER TYPES OF STORAGES
Tertiary storage
Tertiary storage or tertiary memory, provides a third level of storage. Typically it involves a robotic mechanism which will mount (insert) and dismount removable mass storage media into a storage device according to the system's demands; this data is often copied to secondary storage before use. It is primarily used for archiving rarely accessed information since it is much slower than secondary storage (e.g. 5–60 seconds vs. 1–10 milliseconds). This is primarily useful for extraordinarily large data stores, accessed without human operators. Typical examples include tape libraries and optical jukeboxes.
When a computer needs to read information from the tertiary storage, it will first consult a catalog database to determine which tape or disc contains the information. Next, the computer will instruct a robotic arm to fetch the medium and place it in a drive. When the computer has finished reading the information, the robotic arm will return the medium to its place in the library.
Off-line storage
Off-line storage is a computer data storage on a medium or a device that is not under the control of a processing unit. The medium is recorded, usually in a secondary or tertiary storage device, and then physically removed or disconnected. It must be inserted or connected by a human operator before a computer can access it again. Unlike tertiary storage, it cannot be accessed without human interaction.
Off-line storage is used to transfer information, since the detached medium can be easily physically transported. Additionally, in case a disaster, for example a fire, destroys the original data, a medium in a remote location will probably be unaffected, enabling disaster recovery. Off-line storage increases general information security, since it is physically inaccessible from a computer, and data confidentiality or integrity cannot be affected by computer-based attack techniques. Also, if the information stored for archival purposes is rarely accessed, off-line storage is less expensive than tertiary storage.
In modern personal computers, most secondary and tertiary storage media are also used for off-line storage. Optical discs and flash memory devices are most popular, and to much lesser extent removable hard disk drives. In enterprise uses, magnetic tape is predominant. Older examples are floppy disks, Zip disks, or punched cards.
SECONDARY STORAGE
Secondary storage
Secondary storage (also known as external memory or auxiliary storage), differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage. Secondary storage does not lose the data when the device is powered down—it is non-volatile. Per unit, it is typically also two orders of magnitude less expensive than primary storage. Modern computer systems typically have two orders of magnitude more secondary storage than primary storage and data are kept for a longer time there.
In modern computers, hard disk drives are usually used as secondary storage. The time taken to access a given byte of information stored on a hard disk is typically a few thousandths of a second, or milliseconds. By contrast, the time taken to access a given byte of information stored in random-access memory is measured in billionths of a second, or nanoseconds. This illustrates the significant access-time difference which distinguishes solid-state memory from rotating magnetic storage devices: hard disks are typically about a million times slower than memory. Rotating optical storage devices, such as CD and DVD drives, have even longer access times. With disk drives, once the disk read/write head reaches the proper placement and the data of interest rotates under it, subsequent data on the track are very fast to access. To reduce the seek time and rotational latency, data are transferred to and from disks in large contiguous blocks.
When data reside on disk, block access to hide latency offers a ray of hope in designing efficient external memory algorithms. Sequential or block access on disks is orders of magnitude faster than random access, and many sophisticated paradigms have been developed to design efficient algorithms based upon sequential and block access. Another way to reduce the I/O bottleneck is to use multiple disks in parallel in order to increase the bandwidth between primary and secondary memory.
Some other examples of secondary storage technologies are: flash memory (e.g. USB flash drives or keys), floppy disks, magnetic tape, paper tape, punched cards, standalone RAM disks, and I omega Zip drives.
The secondary storage is often formatted according to a file system format, which provides the abstraction necessary to organize data into files and directories, providing also additional information (called metadata) describing the owner of a certain file, the access time, the access permissions, and other information.
Most computer operating systems use the concept of virtual memory, allowing utilization of more primary storage capacity than is physically available in the system. As the primary memory fills up, the system moves the least-used chunks (pages) to secondary storage devices (to a swap file or page file), retrieving them later when they are needed. As more of these retrievals from slower secondary storage are necessary, the more the overall system performance is degraded.
PRIMARY STORAGE
1) Primary storage, also known as main storage or memory, is the area in a computer in which data is stored for quick access by the computer's processor. The terms random access memory (RAM) and memory are often as synonyms for primary or main storage.
Primary storage is volatile and can be contrasted with non-volatile secondary storage, also known as auxiliary storage. The terms main storage and auxiliary storage originated in the days of the mainframe computer to distinguish the more immediately accessible data storage from data stored on punch cards that required input/output (I/O) operations. In the days when mainframe data storage contained ferrite cores, the term core storage was often used in place of primary storage.
2) In the enterprise, the label primary storage is often used to describe storage for data that is in active use, as opposed to data at rest in a backup. In this usage, the label primary storage may actually be describing the non-volatile secondary storage referred to in meaning 1 above. It should be noted that although these two meanings conflict, the appropriate meaning is usually apparent from the context. For example, primary storage in a tiered-storage architecture might consist of hard disks or flash-based solid state drives on a centralized storage-area network (SAN) or network-attached storage (NAS) array that stores transactional data or mission-critical application data that requires extremely high performance.
Huwebes, Setyembre 11, 2014
HARDWARE AND SOFTWARE
HARDWARE
Computer hardware is the collection of physical elements that constitutes a computer system. Computer hardware refers to the physical parts or components of a computer such as the monitor, mouse, keyboard, computer data storage, hard drive disk (HDD), system unit (graphic cards, sound cards, memory, motherboard and chips), etc. all of which are physical objects that can be touched. In contrast, software is instructions that can be stored and run by hardware.
Software is any set of machine-readable instructions that directs a computer's processor to perform specific operations. A combination of hardware and software forms a usable computing system.
Personal computer
The personal computer, also known as the PC, is one of the most common types of computer due to its versatility and relatively low price.Laptops are generally very similar, although may use lower-power or reduced size components.
Case
The computer case is a plastic or metal enclosure that houses most of the components. Those found on desktop computers are usually small enough to fit under a desk, however in recent years more compact designs have become more common place, such as the all-in-one style designs from Apple, namely the i Mac. Laptops are computers that usually come in a clam shell form factor, again however in more recent years deviations from this form factor have started to emerge such as laptops that have a detachable screen that become tablet computers in their own right.
Power supply
A power supply unit (PSU) converts alternating current (AC) electric power to low-voltage DC power for the internal components of the computer. Laptops are capable of running from a built-in battery, normally for a period of hours.
Motherboard
The motherboard is the main component of computer. It is a large rectangular board with integrated circuitry that connects the other parts of the computer including the CPU, the RAM, the disk drives(CD, DVD, hard disk, or any others) as well as any peripherals connected via the ports or the expansion slots.
Components directly attached to or part of the motherboard include:
- The CPU (Central Processing Unit) performs most of the calculations which enable a computer to function, and is sometimes referred to as the "brain" of the computer. It is usually cooled by a heat sink and fan. Most newer CPUs include an on-die Graphics Processing Unit (GPU).
- The Chip Set, which includes the north bridge, mediates communication between the CPU and the other components of the system, including main memory.
- The Random-Access Memory (RAM) stores the code and data that are being actively accessed by the CPU.
- The Read-Only Memory (ROM) stores the BIOS that runs when the computer is powered on or otherwise begins execution, a process known as Bootstrapping, or "booting" or "booting up". The BIOS (Basic Input Output System) includes boot firmware and power management firmware. Newer motherboards use Unified Extensible Firmware Interface (UEFI) instead of BIOS.
- Buses connect the CPU to various internal components and to expansion cards for graphics and sound.
- The C MOS battery is also attached to the motherboard. This battery is the same as a watch battery or a battery for a remote to a car's central locking system. Most batteries are CR2032, which powers the memory for date and time in the BIOS chip.
Expansion cards
The [expansion card] in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard or back plane to add functionality to a computer system via the expansion bus.
Storage devices
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is a core function and fundamental component of computers.
Fixed media
Data is stored by a computer using a variety of media. Hard disk drives are found in virtually all older computers, due to their high capacity and low cost, but solid-state drives are faster and more power efficient, although currently more expensive than hard drives, so are often found in more expensive computers. Some systems may use a disk array controller for greater performance or reliability.
Removable media
To transfer data between computers, a USB flash drive or Optical disc may be used. Their usefulness depends on being readable by other systems; the majority of machines have an optical disk drive, and virtually all have a USB port.
Input and output peripherals
Input and output devices are typically housed externally to the main computer chassis. The following are either standard or very common to many computer systems.
Input
Input devices allow the user to enter information into the system, or control its operation. Most personal computers have a mouse and keyboard, but laptop systems typically use a touch pad instead of a mouse. Other input devices include webcams, microphones, joysticks, and image scanners.
Output device
Output devices display information in a human readable form. Such devices could include printers, speakers, monitors or a Braille embosser.
Mainframe computer
A mainframe computer is a much larger computer that typically fills a room and may cost many hundreds or thousands of times as much as a personal computer. They are designed to perform large numbers of calculations for governments and large enterprises.
Departmental computing
In the 1960 and 1970 more and more departments started to use cheaper and dedicated systems for specific purposes like process control and laboratory automation.
Supercomputer
A supercomputer is superficially similar to a mainframe, but is instead intended for extremely demanding computational tasks. As of November 2013, the fastest supercomputer in the world is the Tianhe-2, in Guangzhou, China.
The term supercomputer does not refer to a specific technology. Rather it indicates the fastest computers available at any given time. In mid 2011, the fastest supercomputers boasted speeds exceeding one petaflop, or 1000 trillion floating point operations per second. Super computers are fast but extremely costly so they are generally used by large organizations to execute computationally demanding tasks involving large data sets. Super computers typically run military and scientific applications. Although they cost millions of dollars, they are also being used for commercial applications where huge amounts of data must be analyzed. For example, large banks employ supercomputers to calculate the risks and returns of various investment strategies, and healthcare organizations use them to analyze giant databases of patient data to determine optimal treatments for various diseases.
SOFTWARE
Computer software, or simply software is any set of machine-readable instructions that directs a computer's processor to perform specific operations. Computer software contrasts with computer hardware, which is the physical component of computers. Computer hardware and software require each other and neither can be realistically used without the other.
Computer software includes computer programs, libraries and their associated documentation. The word software is also sometimes used in a more narrow sense, meaning application software only. Software is stored in computer memory and cannot be touched i.e. it is intangible.
At the lowest level, executable code consists of machine language instructions specific to an individual processor – typically a central processing unit (CPU). A machine language consists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a particular storage location inside the computer – an effect that is not directly observable to the user. An instruction may also (indirectly) cause something to appear on a display of the computer system – a state change which should be visible to the user. The processor carries out the instructions in the order they are provided, unless it is instructed to "jump" to a different instruction, or interrupted.
Software written in a machine language is known as "machine code". However, in practice, software is usually written in high-level programming languages that are easier and more efficient for humans to use (closer to natural language) than machine language. High-level languages are translated, using compilation or interpretation or a combination of the two, into machine language. Software may also be written in a low-level assembly language, essentially, a vaguely mnemonic representation of a machine language using a natural language alphabet. Assembly language is translated into machine code using an assembler.
computer software can be divided into:
- Application software, which uses the computer system to perform useful work or provide entertainment functions beyond the basic operation of the computer itself. There are many different types of application software, because the range of tasks that can be performed with a modern computer is so large - see list of software.
- System Software, which is designed to directly operate the computer hardware, to provide basic functionality needed by users and other software, and to provide a platform for running application software. System software includes:
- Operating systems, which are essential collections of software that manage resources and provides common services for other software that runs "on top" of them. Supervisory programs, boot loaders, shells and window systems are core parts of operating systems. In practice, an operating system comes bundled with additional software (including application software) so that a user can potentially do some work with a computer that only has an operating system.
- Device drivers, which operate or control a particular type of device that is attached to a computer. Each device needs at least one corresponding device driver; because a computer typically has at minimum at least one input device and at least one output device, a computer typically needs more than one device driver.
- Utilities, which are computer programs designed to assist users in maintenance and care of their computers.
- Malicious Software or Malware, which are computer programs developed to harm and disrupt computers. As such, malware is undesirable. Malware is closely associated with computer-related crimes, though some malicious programs may have been designed as practical jokes.
INPUT and OUTPUT
INPUT and OUTPUT
input/output device, also known as computer peripheral, any of various devices (including sensors) used to enter information and instructions into a computer for storage or processing and to deliver the processed data to a human operator or, in some cases, a machine controlled by the computer. Such devices make up the peripheral equipment of modern digital computer systems.
An input device converts incoming data and instructions into a pattern of electrical signals in binary code that are comprehensible to a digital computer. An output device reverses the process, translating the digitized signals into a form intelligible to the user. At one time punched-card and paper-tape readers were extensively used for inputting, but these have now been supplanted by more efficient devices.
Input devices include typewriter-like keyboards; handheld devices such as the mouse, trackball, joystick, and special pen with pressure-sensitive pad; and microphones. They also include sensors that provide information about their environment—temperature, pressure, and so forth—to a computer. Another direct-entry mechanism is the optical laser scanner (e.g., scanners used with point-of-sale terminals in retail stores) that can read bar-coded data or optical character fonts. Output equipment includes video display terminals (either cathode-ray tubes or liquid crystal dsplays), ink-jet and laser printers, loudspeakers, and devices such as flow valves that control machinery, often in response to computer processing of sensor input data. Some devices, such as video display terminals, may provide both input and output. Other examples are devices that enable the transmission and reception of data between computers—e.g., modems and network interfaces. Most auxiliary storage devices—as, for example, magnetic tape, magnetic disk drives, and certain types of optical compact dics—also double as input/output devices (see computer).
Various standards for connecting peripherals to computers exist. For example, integrated drive electronics (IDE) and enhanced integrated drive electronics (EIDE) are common interfaces, or buses, for magnetic disk drives. A bus (also known as a port) can be either serial or parallel, depending on whether the data path carries one bit at a time (serial) or many at once (parallel). Serial connections, which use relatively few wires, are generally simpler and slower than parallel connections. Universal serial bus (USB) is a common serial bus. A common example of a parallel bus is the small computer systems interface, or SCSI, bus.
COMPUTER
COMPUTER
A computer is a machine which helps us to calculate, simulate and store different scenarios. For example, in order to write an e-mail, instead of paper and pen first we use a software (or program) called word processor which helps us enter sentences through keyboard (Input), computer's screen (output) to read, and modem (output/input) to send it to a distant relative, friend, etc.
The mechanism to simulate a regular mail into an e-mail, gave us a very fast and much cheaper medium to communicate (not a simulation anymore). Same way, using computers we can simulate other things over which we do not have any control, for example weather, behaviour of atomic bomb, behavior of a deadly virus, Earthquake, a innovative design for a new auto, airplane, machine, etc.
Any computer has five parts Input, Output, CPU, Memory, disk (storage) . Input is things like mouse, keyboard, modem. Output is computer screen, printer. CPU or central processing is brain of the computer which controls and execute all calculations, manipulations and output. Memory (RAM)is a temporary storage to be used by CPU when doing calculations, etc. Think of it as a scratch pad for CPU. Disk is permanent storage, on which all the software and data is stored.
When you turn on your computer, BIOS (or basic input output system) which resides on CMOS (complimentary Metal Oxide semiconductor,a type of chip) has small coded software written on it which tells CPU to read the next instruction from sector n of disk x. This next instruction loads the operating system.
A computer is a machine which helps us to calculate, simulate and store different scenarios. For example, in order to write an e-mail, instead of paper and pen first we use a software (or program) called word processor which helps us enter sentences through keyboard (Input), computer's screen (output) to read, and modem (output/input) to send it to a distant relative, friend, etc.
The mechanism to simulate a regular mail into an e-mail, gave us a very fast and much cheaper medium to communicate (not a simulation anymore). Same way, using computers we can simulate other things over which we do not have any control, for example weather, behaviour of atomic bomb, behavior of a deadly virus, Earthquake, a innovative design for a new auto, airplane, machine, etc.
Any computer has five parts Input, Output, CPU, Memory, disk (storage) . Input is things like mouse, keyboard, modem. Output is computer screen, printer. CPU or central processing is brain of the computer which controls and execute all calculations, manipulations and output. Memory (RAM)is a temporary storage to be used by CPU when doing calculations, etc. Think of it as a scratch pad for CPU. Disk is permanent storage, on which all the software and data is stored.
When you turn on your computer, BIOS (or basic input output system) which resides on CMOS (complimentary Metal Oxide semiconductor,a type of chip) has small coded software written on it which tells CPU to read the next instruction from sector n of disk x. This next instruction loads the operating system.
A database is a software which lets user to organize their data in an orderly fashion. For example consider a company which sells cookies, they have a database of which has tables (or records) of customers, types of cookies and orders. So when customer x orders n number of x type of cookies his orders is placed in table orders. There are several type of databases. Some which are simply text files with records, others which are complex with tables of information. A table of information means "an array of one type of records", for example "an array of customer names, addresses, phone numbers". A Relational database is in which there are relations among the tables, for example consider three tables with customer info, inventory info and orders info. The relations between these three tables define the relational database. So when a customer X from customer table orders Item Y from Inventory info it is put in Orders table, there are links in these tables (through primary keys, secondary and foreign keys such Social Security number, product number, order number, etc) which lets us do that and thus making it a relational database. Popular type of relational databases are Access for PCs on windows 95, Oracle, Sybase, Informix, for huge business environment (running Unix operating systems).
Internet is a bunch of computers connected to each other. It started out when about 10 computers running Unix operating systems serving US military were connected to each other and named ARPANET. Initially, users could only send an e-mail to each other, deploying UUCP (unix to unix copy using modems) method. Then more computers from universities were added to ARPANET and research individuals started sharing their notes over e-mail. Later came Usenet which was more or less a discussion forum. Then after tremendous innovations in hardware (networking), in 1992 came Web, or the software called web browser which could display pictures and text. REST is history. Some terms
Programming languages are designed to aid humans to write code for computers. Since computers only understand the language of o's and 1's, and we humans a common english like languages, several computer languages were developed which translate code to computer language. Programming languages like C/C++,Visual Basic, Java using these a person writes a code and then compiles it and creates an executable file which is understood by machine. All .exe and .class files are executable files translated into language understood by computer.
Networking constitutes of connecting PCs and other machines with each other. If you have bunch of computers in same building connected to servers through several hubs it is a Local Area Network, like in an office building. If you have many buildings with many computers connected to each other it is a WAN or wide area network, like Universities. Going by same terminology Internet is probably Global Area Network. Servers are those computers which control user access to files, and are running all the time. All of the computers which are connected to Internet are servers since Internet demands access to information round the clock. When you use modem to connect to Internet on your Personal computer, you are connecting to a computer which is connected to Internet.
Operating systems are that piece of software which communicate with computer and converts all user commands back and forth. Operating systems have four parts which are Process manager, Memory manager, I/O manager and . Popular operating systems are Windows 95, Windows 98, Windows NT, Mac, SunOs, Digital, HP-UX, Solaris, Aix, etc.
Applications are the end user products which user run on a computer. i.e. Games, Word processing, excel, word, are all applications.
Personal computers are those machines that sit on your desk at home or at office, usually running Windows 95, MacOs, windows 3.1, windows 98, windows NT workstation, and other operating systems designed for PCs. Servers usually run more robust Operating systems like Unix, Windows NT, etc.
Internet is a bunch of computers connected to each other. It started out when about 10 computers running Unix operating systems serving US military were connected to each other and named ARPANET. Initially, users could only send an e-mail to each other, deploying UUCP (unix to unix copy using modems) method. Then more computers from universities were added to ARPANET and research individuals started sharing their notes over e-mail. Later came Usenet which was more or less a discussion forum. Then after tremendous innovations in hardware (networking), in 1992 came Web, or the software called web browser which could display pictures and text. REST is history. Some terms
Programming languages are designed to aid humans to write code for computers. Since computers only understand the language of o's and 1's, and we humans a common english like languages, several computer languages were developed which translate code to computer language. Programming languages like C/C++,Visual Basic, Java using these a person writes a code and then compiles it and creates an executable file which is understood by machine. All .exe and .class files are executable files translated into language understood by computer.
Networking constitutes of connecting PCs and other machines with each other. If you have bunch of computers in same building connected to servers through several hubs it is a Local Area Network, like in an office building. If you have many buildings with many computers connected to each other it is a WAN or wide area network, like Universities. Going by same terminology Internet is probably Global Area Network. Servers are those computers which control user access to files, and are running all the time. All of the computers which are connected to Internet are servers since Internet demands access to information round the clock. When you use modem to connect to Internet on your Personal computer, you are connecting to a computer which is connected to Internet.
Operating systems are that piece of software which communicate with computer and converts all user commands back and forth. Operating systems have four parts which are Process manager, Memory manager, I/O manager and . Popular operating systems are Windows 95, Windows 98, Windows NT, Mac, SunOs, Digital, HP-UX, Solaris, Aix, etc.
Applications are the end user products which user run on a computer. i.e. Games, Word processing, excel, word, are all applications.
Personal computers are those machines that sit on your desk at home or at office, usually running Windows 95, MacOs, windows 3.1, windows 98, windows NT workstation, and other operating systems designed for PCs. Servers usually run more robust Operating systems like Unix, Windows NT, etc.
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