Knowledge

     Knowledge is a static concept for information systems. The dictionary meaning of this concept can be given in three different ways without using the word  information :

1. Something learned and kept in mind,

2. Clear perception of truth,

3. Understanding gained by actual experience,

     This entity means that something obtained and stored.The procedures, learning, perception and understanding are not involved in the content of this concept.So it is not dynamic entity, it is static.

Information

     In contrast to the knowledge concept, information is a dynamic entity. Its dictionary meaning can be given as follows.

1.  The communication or reception of knowledge or intelligence,

2.  Knowledge obtained from investigation, study, or instruction

     The first item defines a dynamic entity since its main theme is either communication or reception which corresponds to a verbal action. However the second item is related to a more static concept. Although the main component of the definition is the knowledge which is certainly static, the obtaining of this thing necessitates some efforts or actions since the procedures, investigation, study or instruction are dynamic concepts. Therefore we can assume that the information concept is a dynamic entity without any appearable loss of generality. On the other hand, the definition for the concept of information is based on the knowledge concept. Hence, the knowledge is a required thing or a brick for the construction of the information.

Informatics

     This word was produced from the word information by replacing its last four characters with ics in 1967. It is a plural noun but is used as a singular entity in the construction of sentences or expressions. It was related to the statement  Information Sciences which was first used in 1960. Starting with the year 1967 the term Informatics was used instead of the statement Information Science.

     The dictionary meaning of informatics can be given as it the collection, classification, storage, retrieval, and dissemination of recorded knowledge treated both as a pure and as an applied science}.

Counting

     Counting is a very important action in human life. All tradings, and balance in the economical system of humanity is based on counting during the evolution of the human social life. However, this is not the only important point of the need for computation. In fact, he whole scientific developments, implicitly or explicitly, were built on the concept of counting.

     Historically, the beginning of the counting in the human social life lies at the very early ages of the human evolution. The counting is a comparison procedure and aimed to the determination of the population of some elements in a specified collection. Mathematically speaking, it uses two different sets whose first one is the set to be counted while the second is the reference set. The procedure tries to establish a one--to--one correspondence between the elements of these two sets. For example, consider a classroom involving a specified number of seats and a group of students. The comparison procedure here aims to determine whether the population of the students is greater than, equal to, or less than the population of the seats. The procedure produces a unique answer which decides the valid one of these possibilities. Of course, this is just a raw process and we can use either students or seats as the reference set. To develop a more sophisticated precise comparison we need to use a unique and universal set. This can be chosen as the set of positive integers. Then the comparison procedure turns out to be the determination of a positive integer subset which is ordered and contains all the integers between 1 and the number of its elements inclusive. If we can find a subset such that a one--to--one correspondence can be established between the elements of the set to be counted and this subset then the number of elements in the set to be counted is the size (the number of elements) of this reference subset of positive integers. In mathematical point of view this is the precise definition of counting.

Number Systems

     The numbers are the essential components of quantitative sciences. Their definitions and historical developments are involved in the number theory of pure mathematics which is out of the scope of this course. However, they re also main elements of information processing and therefore computer science in the perspective of applied mathematics. We need to know their representations in symbols.

     During the historical development of humanity mankind mostly used hands and fingers. Since the total number of fingers in two hands of humans are 10, the decimal number system became overruling number system. If the total number of the fingers were a different value then that value would be the base of the number system. We have mentioned the base concept of the number systems. Now, it is time to introduce the basic definition of the number system. To this end we need to recall the number representation. We first deal with the integers. According to the one of very famous theorem of the number theory, any given number can be resolved into the following linear combination

where n is the number to be represented in the number system whose basis, b, is a positive integer. The coefficients of the above linear combination can take values from the set {0,1,2,3,...,b-1}. Each of these values for coefficients is individually denoted by a unique single symbol. These symbols are composed of the arabic numerals {0,1,2,3,...,9}. If we denote these single symbols by s1,s2,...,sb then the number system becomes uniquely defined. In the above example, the numbersystem is called b--based number system . If the number under consideration, say p, is not an integer then the finite linear combination turns out to be the following infinite expansion

where the coefficients of this expansion can take the values only from the set s1,s2,...,sb.

     In the practical applications the representation is more concise than the above expansion and only the coefficients are used in the representation as follows

where the parentheses and the index b are used to specify the number system more clearly. In decimal notation, or in the notations which use the same number system without passing to some other ones, the parentheses and the index b can be considered unnecessary.

Decimal System

     Decimal system is a number system which uses 10 as the base. Its digit symbols are arabic numerals 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. The standard arithmetic rules are used for arithmetic operations amongst these numbers. Since it is very well--known from the high school years and from our daily life we do not intend to give more details about this system.

Binary System

     For the moment, computers can only use the electronic devices like chips, microchips which can be considered as a combination of zillions of the microscopic switches such that each switch can have only two positions, open or closed. Hence, each switch can store two option knowledge which can be represented by either 0 or 1. That is, each switch can store a single bit. This means that computers can not use decimal system in its chips since this system's knowledge units are composed of ten different options, that is, 0, 1, ..., 9. The two option structure in the memory architecture %of the computers necessitate the utilization of the binary system whose base is 2 and the digital symbols are 0 and 1. A binary number can be composed of 0s and 1s only. The conversion between the decimal representation and binary representation of the same number follows the instructions given in the high school years. One important thing to be emphasized is the number of the digits in the representations. The binary representation generally contains more digits than the decimal represention for the same number. The student is assumed to be familiar with the algebra for these representations.

Octal Systems

     The octal system's base is 8 and the digital symbols are 0, 1, 2, 3, 4, 5, 6, 7. It is used in the informatics science because of its conciseness. As a matter of fact, a binary number can be separated into three digit groups from right to left and then each individual group can be converted into an octal number. The result is replaced with the corresponding three binary digit group. The finally obtained number which is an octal number has three times less digits than its binary counterpart. The conversion from octal to binary representation is realized by using an opposite, digit expansion, technique.

Hexadecimal Systems

     The  hexadecimal system's base is 16 and the digital symbols are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C. D, E, F. It is used in the informatics science because of its conciseness. As a matter of fact, a binary number can be separated into four digit groups from right to left and then each individual group can be converted into a hexadecimal number. The result is replaced with the corresponding four binary digit group. The finally obtained number which is a hexadecimal number has four times less digits than its binary counterpart. The conversion from hexadecimal to binary representation is realized by using an opposite, digit expansion, technique.

Information Units, BIT and BYTE

     To deal with the knowledge in quantitative scale we need to define units for it. Nowadays, we use computers and related hardwares, to process knowledge. Since the he computer memories are designed to have switches which have only two options (open or closed) it is quite natural to use binary system for number representation. This means that the atom of the knowledge is a unit which can have only two options, 0 or 1. The binary digits are composed of 0s and 1s. So it is natural to define the smallest unit of the knowledge as binary digit. The late professor of Princeton University, John Tukey who was a famous leading statistician and adviser to five presidents of USA proposed the term BIT for this smallest unit in 1946. He used the statement Binary digit and took the capitalized letters to construct this term. Hence, BIT is an acronym for binary digit.

The Concepts of Hardware and Software

     The term hardware implies the objects whose existence can be percepted via the sense organs of human body. These are touchable items like disks, disk drives, display screens, keyboards, printers, boards and chips.

     The term software which was first used by John Tukey means computer instructions or data. All electronically storable items are software. The existence of software can not be percepted via human sense organs. It is an untouchable thing. It is conceptual or virtual. People generally confuses the meaning of hardware and software. To make the distinction of these two terms more clearer we can consider a book which contains papers and ink and also information written onto its pages. The papers and ink are hardware while the information included as written form in the pages is software. Similarly, a hard disk and its pieces are hardware while the programs or data stored in the hard disk is considered as software.

Computing Systems in Human History

     There had been a lot of different computing systems invented during the scientific evolution of the humanity. The humankind started with the fingers for constructing a computing system although there were some signals of the existence of a twenty based numbers system used by the ancient northwest french tribes. If they are true one may expect that they possibly used their fingers and toes together for computation.

     The only necessity for creating a computing system was not, of course, counting. The four fundamental arithmetic operations also necessitate a computing device to facilitate the computing procedure. The first device for computation is known as abacus which uses counter balls on rods. It was designed for arithmetic operations, mainly addition, subtraction and multiplication. There are some historical findings about the existence of a string system in South America ancient nations like Inca. The string were containing nodes and a comparison procedure around the nodes and strings were enabling the humankind to use it in calculations.

     In the second half of the second millenium, there had been efforts to invent more complicated devices which can be used more comprehensively. The son of a tax officer, Blaise Pascal, was one of the pioneers in this direction and he designed a mechanical calculator to relax his fathers intensive business life. The mechanical device inventions continued and resulted in the birth of famous company IBM (International Business Machines).

     After the years which brought the utilization of electricity to the applications at everywhere the efforts were concentrated on the construction of an electrical calculator. The employment of vacuum tubes, transistors, chips and microchips rapidly increased the storage and processing capacity of these devices and yield to the today's computers. In the following sections some important items of these devices are given.

Transistor

     This is a semiconductor material involving device amplifying a signal or opens or closes a circuit. It is invented in 1947 at Bell labs and have become the key ingredient of the digital circuit. Today's microprocessors contain tens of millions of microscopic transistors.

     Before the invention of the transistors, digital circuits were composed of  vacuum tubes. They had many disadvantages such that they were large in size, required more energy, dissipated more heat and they were more prone to the failure.

Integrated Circuit

     This is another name for chip. It is a small electronic device which is made out of a semiconductor material. Its first version was developed in the 1950s by Jack Kilby of Texas Instruments and Robert Noyce of Fairchild semiconductor.

Printed Circuit Board

     This is sometimes abbreviated PCB. It is a thin plate on which chips and other electronic components are placed. Computers may contain one or more than one PCBs. The varieties for these boards spreads on a spectrum containing mother board, expansion board, daughtercard, controller board, Network Interface Card (NIC), video adapter.

Chips

     This is a small piece of semiconducting material which is usually silicon. An integrated circuit is embedded on this small piece. A typical chip is less than 1/4 square inches. It contains millions of electronic components like transistors. The devices which have sizes roughly million times less than usual chip's size are called microchip. Sometimes, the word micro might not be used to recall million but something very small in comparison with the usual sizes.

     The hardware technology is now at the level of nanometer sizes. Delicate devices are used for the production of nanometer level devices. The next step for the miniaturization of the hardware might be picometer but quantum phenomena becomes dominant at that level and the controlling devices may not be constructed by using today's technology. So the miniaturization level will approach, soon or later, to a dead end.

     On the other hand, scientists tries to use the controlled spins of the atoms for knowledge storage. This increases our hopes for opening a new era for the miniaturization of the computers. Additionally, the possibility of using spins which may take more than two values implies the abandonment or strengthening of the binary system. The use of more than two state spins may open a new phase where other number systems can be used. This means more knowledge storage than the designs based on binary system for the same size of hardware. Although they are not practically tested and even not constructed, they are called quantum computers.

Cache

     The term  cache which is pronounced  cash is a special hihg--speed storage mechanism. It can be a reserved section of the main memory or can be designed as an independent high--speed storage device. This storage mechanism is sometimes called caching which is pronounced cashing. In personal computers there are two commonly used caching: memory caching and disk caching.

      Memory cache is sometimes called cache store or RAM cache is a portion of memory made of SRAM which is a high--speed static random access memory. It does not use DRAM which is a slower and cheaper dynamic random access memory. Memory caching is effective because most programs access the same data or instructions over and over.

      Disk caching is based on the same principle as memory caching. It does not use SRAM. Instead, it uses conventional main memory. The most recently accessed data from the disk is stored in a memory buffer. A program first checks the disk cache to see if the data is there when it needs to access a data from the disk. The accessing to the data in the adjacent sectors of the main memory is handled in the same way.

Computer Memories

     There are several different type of memory units in a computer. The hardware design and purposes are different for these units. In some of the following sections we give certain information about these items.

RAM

     RAM is an acronym for the statement Random Access Memory. It is same as the main memory. When employed by itself RAM refers read and write memory. That is, it is possible to read data from or to write data into this type of memory. RAM is mostly a volatile device. That is, it requires electricity to hold its content. When the electricity breaks down the content becomes unrecoverably unavailable.

     There are some other types of the random access memories. Amongst these, DRAM which is an acronym for the statement Dynamic Random Access Memory and SRAM which is an acronym for the statement Static Random Access Memory can be given as examples.

ROM

     ROM is an acronym for the statement Read Only Memory. It holds the instructions for starting up the computer. The content is written by the producer company during the construction of the computer. The ROM can not be written to unlike RAM.

PROM

     PROM is an acronym for the statement Programmable Read Only Memory. It is a memory chip on which a program can be stored. However once the PROM has been used it can not be wiped clean and can not be used to store something else. In other words, PROMs are nonvolatile like ROMs.

EPROM

     EPROM is an acronym for the statement Erasable Programmable Read Only Memory. It is a special type of PROM which can be cleaned by exposing it to ultraviolet light.

EEPROM

      EEPROM is an acronym for the statement Electrically Erasable Programable Read Only Memory. It is a special type of PROM which can be cleaned by exposing it to electrical charge.

Floppy Disk

     The term floppy disk is used for a soft magnetic disk. The commercially available first version of floppy disks had 5,25 inch diameter. It was called floppy because the 5,25 inch variety of these disks flop when it is waved. Floppy disks are generally called just floppies or diskettes. They are portable because they can be removed from the disk drive without dismounting the computer. Disk drives for floppies are called floppy drives. Floppies are slower than the hard disks and their storage capacity is lower than hard disk capacities. But they are less expensive than hard disks.

Hard Disks (IDE, SCSI)

     The term hard disk is used for a magnetic disk on which computer data can be stored. The term hard is used to distinguish it from the floppies. Their storage capacity is very large in the comparison with the floppies and they are very faster than floppies in data transfer.

     A single hard disk is usually composed of several platters. Each platter requires two read/write heads, one for each side. These heads can not move independently since they are attached to the same arm. Each platter has the same number of tracks. A track location cutting across all platters is called cylinder. Although you may find removable hard disks, they are less portable than floppies.

      The interfaces which are used in data transmission from/to hard disks may vary. One of most common interface is IDE which is an acronym for either  Intelligent Drive Electronics or   Integrated Drive Electronics depending on whom to be asked. In IDE interface the controller is integrated into the disk or CDROM device.

     The other well--known interface is called SCSI which is pronounced scuzzy is an acronym for the statement   Small Computer System Interface. It is a parallel interface standard. For this interface a special type port SCSI port is used. This enables us to attach many devices to the same port. The interface is faster than parallel and serial ports.

RAID

     RAID is an acronym for the statements Redundant Array of Independent Disks or Redundant Array of Inexpensive Disks}. This is a category of disk drives employing two or more drives in combination for fault tolerance and performance. They are frequently used on servers but not for personal computers generally.

Tape Drive

     Tape drive is a peripheral device, like a tape recorder. It reads data from and writes it onto a tape. Their well--known disadvantage is their sequential structure. There is no capability of random accessing so it may take a very long time to get a specified data from tha tape.

CPU: Central Processing Unit

     CPU is an acronym for the statement  Central Processing Unit. The CPU can be considered as the brain of the computer. It is sometimes referred as the processor or central processor. The CPU is the place of computer where most calculations take place. In the computing point of view CPU is the most important part of computer.

     On large machines, CPU's may necessitate one or more printed circuit boards while on small workstations and personal computers, the CPU is housed in a single chip which is called microchip.

Assembly Language, Assembler

     Assembly language is a programming language which makes the machine language codes more amenable for the humans. Machine language are only composed of numbers. However, assembly language can use names or words which are more meaningful for humans although its instruction structure is same with the machine language.

     Assembly language is tightly dependent on the architecture of the CPU under consideration as the machine languages behave in the same fashion. In other words, an assembly language designed for a specific processor does not run for a different CPU as the machine language does the same thing.

     Assembler means a program which translates programs from assembly language to machine language.

Keyboard

     A computer keyboard is a device containing type--writer like keys which enables us to enter data into a computer. They are similar to the keyboards of the electronic type--writer keyboards but they contain some additional keys. The keys of a computer keyboard can be categorized into three classes, the first of which is called alphanumeric keys which are composed of letters and numbers. The second class is called punctuation keys which contain comma, period, semicolon and similar punctuation symbols while the third class is called special keys which involve function keys, control keys, arrow keys, Caps Lock key and similar keys which have special verbal actions.

Monitor

     The term monitor was first used for the statement display screen. However, today it has a broader meaning since now monitor implies the entire box of the device while display screen recalls just the screen. Additionaly, monitor often implies graphics capabilities. The classification of the monitors is not unique. However the most basic way for the classification takes the color capabilities into account. In this sense there are three group of monitors. The first one is called monochrome which display two colors one for background and one for foreground. These colors can be black and white or gray and white or amber and black. The second group monitors are called grayscale monitors. A grayscale monitor is a special type of a monochrome monitor. It is capable of displaying different shades of gray. The third group of monitors are called color monitors. These can display anywhere from more than 1 million to 16 million different colors. They are sometimes called RGB monitors because they accepts three separate signals, red, green and blue.

Mouse

     Mouse is a cursor or pointer control device. It controls the location and the movement of the cursor or pointer on a display screen. It is a small object which can be rolled along a hard, flat surface and its name is derived from its shape. It looks a bit like a mouse because its connecting wire recalls the mouse's tail. It is invented by Douglas Engelbart of Stanford Research Center in 1963. Mouse is a great break--through in computer ergonomics because it makes free the user to a large extent from using the keyboard.

Printers

     Printer is a peripheral device for computers. It prints text or illustrations on paper. There are a lot of different type printers. They can be categorized into seven groups in terms of the technology they use.

     The first one which is called daisy wheel and composed of a ball and ribbon. These devices can not print graphics.

     The second group is called dot--matrix. It creates the characters by striking pins against an ink ribbon. While the each one of the pins make a single dot the

combination of the dots forms the characters and illustrations.

     The third group is called ink jet. It sprays ink at a sheet o paper. These produce high--quality text and graphics.

     The fourth group is called laser. They use the same technology as copy machines.

     The fifth group is named by the acronym LCD\&LED. They are similar to the laser printers but they use either liquid crystal diode or light emitting diode to produce an image on the drum.

     The sixth group is called line printer. They contain a chain of characters or pins and can print an entire line at a single stroke. Although they are very fast the quality of the output is quite low.

    The seventh type is the thermal printer. It pushes heated pins against a heat--sensitive paper. They are used in calculators and fax machines.

Scanners

     A scanner is a peripheral device for computers. It can read text or illustrations printed on paper and translate the information it gathers into a form a computer use. The image is digitized by dividing the image into grid of boxes. Each individual box is represented either 0 or 1. 1 means a full box. The gray scaling and color perception may be possible but in that case each box is represented by 24 bits.

Digitizing Tablets

     A digitizing tablet is a peripheral device for computers such that they enable user to enter drawings and sketches into a computer. It consists of an electronic tabler and a cursor or a pen. In the digitizing tablet each point on the tablet uniquely corresponds to a point on the screen whereas the mouse works in relative movements by referring the cursor position.

Communication Devices

    Communication devices imply the hardware facilities enabling the computer nodes to communicate through the available connections. Here we mention th ethernet cards, modems and connection hardware.

Ethernet Cards

     The term ethernet is used for a local area network protocol developed by Xerox Company in cooperation with DEC and Intel in 1976. The hardware which is a special card to be used for this protocol is called   ethernet card. The data transfer rate through ethernet was 10 Mbps (an acronym for mega bits per second). The later version of the ethernet which had a data transfer rate of 100Mbps was called fast ethernet. The most recent version of the ethernet supports a data transfer rate of 1 Gigabit (1000 megabits) per second and is called  gigabit ethernet.

Modem (Dialup, Null)

     The term modem is an acronym for the statement MOdulator -- DEModulator where the capitalized letters are used to form the acronym. The term {modem} is used both the hardware device and the program used for the connections. It enables a computer to transmit data over telephone lines. The information storage in a computer is at digital level whereas the information transmitted over telephone lines are analog waves. Modem makes conversions between these two forms.

     Modem can also be used for the data transmission between two serially connected computers. In this case the device does not use the dialup signals and is called null modems while the telephone line connected modems are {dialup modems} although the word dialup is generally ignored whenever there is no danger of confusion.

Connections (Parallel, Serial)

     The personal computers use both parallel and serial connections. The connections between the computer and its peripheral devices are satisfied by using the connection points which are called ports. A port is parallel if it is a connection point for a parallel connection. Otherwise it is called serial. There is at least one serial port in a personal computer. In the parallel connections the data transmission takes place in a parallel fashion, that is, more than one synchronous data transmission occur. Whereas in the serial data transfer, the data is tranferred in data trains, that is, there is only one single transmission. The parallel connection is used to connect a computer to its peripheral printer. On the other hand, mouse for example, is serially connected to its computer.