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HTML H yper T ext M ark-up L anguage uses explicit marks also called tags for styling. <b> this sentence is b

HTML H yper T ext M ark-up L anguage uses explicit marks also called tags for styling. <b> this sentence is bold </b>.

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HTML H yper T ext M ark-up L anguage uses explicit marks also called tags for styling. <b> this sentence is b

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  1. HTMLHyper Text Mark-up Language uses explicit marks also called tags for styling. <b> this sentence is bold </b>. Even though these tags will show on your computer screen when creating the text, only their effect will appear when the document passes through a software that interprets these tags and renders you the final display. HTML – an electronic mark-up language 6/7/2014 ArabOU - M150 - AbuNawaf 1 1

  2. Tags in HTML are enclosed within angle brackets < and >. Tags usually come in pairs, there is a start tag before the text to be styled and an end tag after the text to be styled. The end tag always include a slash (/) after the < and before the tag name. HTML is not case sensitive. An introduction to using HTML 6/7/2014 ArabOU - M150 - AbuNawaf 2 2

  3. The basic skeleton to produce an HTML document is the following: <HTML> <HEAD> </HEAD> <BODY> <P> </P> </BODY> </HTML> An introduction to using HTML .. continue 6/7/2014 ArabOU - M150 - AbuNawaf 3 3

  4. What does multimedia refer to ? In order to insert an image into an HTML document an image tag is needed. <IMG SRC=“image.jpg”> If the image is not in the same folder as the document then the complete path needs to be indicated as the source. Note that the <IMG> tag is one of the few tags that are single and go without a closing tag </IMG>. What does hypermedia refer to ? Combining representations-hypermedia Multiple and multimedia Integrating representations Beyond hypertext - hypermedia 6/7/2014 ArabOU - M150 - AbuNawaf 4 4

  5. The HTML language has its weaknesses. The number of tags is limited and they do not cover special styling needs. They are only for: styling including other materials (such as pictures) Linking Beyond basic mark-up: introducing XML Revisiting and extending tags The limitations of HTML tags 6/7/2014 ArabOU - M150 - AbuNawaf 5 5

  6. The XML language (eXtensible Mark-up Language) served for the creation of new tags to which the programmer can give rules as he wishes. Note that XML is NOT a replacement for HTML. HTML describes the style of a document, XML is used to describe the substance of the document. XML describes the information using Types. The addition of tags to HTML is not a simple task, if the World Wide Web Consortium has to study all the proposed tags for approval and addition, the process can go forever unsolved. Revisiting and extending tags 6/7/2014 ArabOU - M150 - AbuNawaf 6 6

  7. Storing text-based data in documents • The lowest level of the hierarchy  documents • This is called a hierarchical or nested folder structure, because each folder may contain other folders • An Explorer window has two panes. The right-hand pane is a folder window (content can be displayed as icons or as a list). • The left-hand pane does not show any documents, but it does show hard disks, folders and any icon which holds other items (e.g. ‘network share’). 6/7/2014 ArabOU - M150 - AbuNawaf 7 7

  8. Storing text-based data in documents ..count • With a bit of imagination, you can think of the folder structure loosely as a tree lying on its side. The desktop is the root of the tree, and each folder is a branch. The leaves of the tree correspond to documents. • Any similar hierarchical arrangement of objects is frequently called a tree structure or just a tree. 6/7/2014 ArabOU - M150 - AbuNawaf 8 8

  9. Storing text-based data in documents ..count • How many documents/folders should you keep in a single folder? There is no limit !! Preferably do NOT exceed 20! • There are two distinct folders called ‘mail’ (prev. figure) but no confusion arises because each is in a different place and has a different path leading to it. • A path contains the names of all the folders that lead to it from the root. • In effect a path allows you to identify unambiguously a folder or document and is often referred to as its full name or full path name (documents in the same folder must have different names). 6/7/2014 ArabOU - M150 - AbuNawaf 9 9

  10. Storing text-based data in documents ..count The Search/Find function • Search function  find items you have ‘lost’. In Windows XP, the search will begin in ‘My Computer’ (or elsewhere by using the drop-down list). • Consider the Windows path name: C:\Projects\M150\Assignments\TMA02.doc ‘C:’ is the root. ‘Projects’ is the name of a folder at the top level of the hard disk which contains a folder called ‘M150’ which in turn contains an ‘Assignments’ folder. The document ‘TMA02.doc’ is in the ‘Assignments’ folder. • Another place where you can see full path names is in a ‘Search Results’ window. 6/7/2014 ArabOU - M150 - AbuNawaf 10 10

  11. Storing text-based data in documents ..count Directories • Each folder has a list, or directory, of the folders and documents that it contains (A folder is sometimes loosely referred to as a directory !!!) • Part of the directory for a given folder can be displayed on screen in a number of ways (alphabetically , in order of last modification date, size , type …) to aid human identification of the contents. • The directory of a folder also lists the address or physical location (more discussion to come!) on the disk of each document and subfolder in that folder. This address is internal to the operating system and cannot be seen in a user window. 6/7/2014 ArabOU - M150 - AbuNawaf 11 11

  12. Storage technologies • There are various technologies of data storage: Storing data can be on the hard disk (typically is built into your computer) or on removable storage media such as CDs, DVDs, Zip disks, high-capacity tape cartridges… • There are various measures of storage size (Capacity): Gigabytes and terabytes PS:‘kilo’ usually means 1,000 but in computing it denotes 1024 (210) 6/7/2014 ArabOU - M150 - AbuNawaf 12 12

  13. Hard disk storage • Nowadays a typical PC comes with a 40/80 GB hard disk • The general principle of hard-disk storage: coated with a magnetic material that can be magnetised into a pattern representing a sequence of bits i.e the surface consists of millions of tiny magnets, which can each be magnetised in two possible directions representing 1 or 0. • A hard disk is 1 to 3 inches in diameter, and consists of one or more circular plates (aluminum, ceramic or glass…), each having two surfaces. • Data is recorded on each surface by magnetising a series of concentric circles called tracks. 6/7/2014 ArabOU - M150 - AbuNawaf 13 13

  14. The disk surface is divided into a number of equal sized wedge-shaped regions called sectors. Within a sector each track holds the same amount of data – usually 512 bytes. • This is the basic unit of data handled by the disk control mechanism, and is called a block(each block of data is guaranteed to be the same size). Question:How can a sector hold the same amount of data on each track when the outer tracks are large than the inner tracks? (check answer on page 14) 6/7/2014 ArabOU - M150 - AbuNawaf 14 14

  15. Removable storage media devices • Read/Write floppy disks: capacity limited to 1.4MB. • Zip drive: 100MB or 250MB capacity • Memory card: A removable medium which is very popular (works on a principle that will not be discussed here). • Optical discs: • CD (compact disc) • DVD (digital versatile disc): Store documents using a different technology based on the optical properties of the surface. The capacity of a CD is 650MB and data is stored on only one side of it in a single spiral groove which winds round the disc 22,188 times. 6/7/2014 ArabOU - M150 - AbuNawaf 15 15

  16. Removable storage media devices .. continue • The data is packed uniformly along the groove, so that outer tracks of the groove hold more data than inner ones ( the disc spins more slowly when accessing data near the centre) • Conventional CDs are called CD-ROMs (Read-Only Memory), and have bits of data stored as ‘pits’ in their groove. Beams of laser light are used to burn the pits on the disc. A CD drive works by shining a low-power laser beam on the disc, which detects the presence or absence of a pit (the pits do not reflect the light). • DVDs (also called DVD-ROMs) pack the data more tightly, using smaller pits and a narrower groove which increase the capacity of a simple DVD to 4.7GB (Some DVDs use both sides having one or two layers each, yielding a theoretical maximum capacity of 19MB). 6/7/2014 ArabOU - M150 - AbuNawaf 16 16

  17. Hard disks vs. Optical disks • One important difference between CD/DVD-ROM discs and magnetic disks is the ability to write to them (once a pit has been burned, it cannot be erased). • There are two kinds of CDs: • Recordable CDs, known as CD-R. Instead of burning pits on the CD, the writing process dyes the relevant parts of the groove. When read by a CD drive these dye spots are indistinguishable from pits on a conventional CD. The process is not reversible. • Rewritable CDs, known as CD-RW, use a different technology altogether (heat a point on the disk to one of two temperatures corresponding to different states of the material). This process is reversible. 6/7/2014 ArabOU - M150 - AbuNawaf 17 17

  18. Labeling volumes • A hard disk or Zip disk or CD is called a volume. • Identifying a CD or other removable medium is necessary. It is important that each is given a label with a title. The volume can be stored in a rack with many similar looking ones but can be identified by its external label. • Besides its physical label a volume should also have an electronic label, which, for consistency, should be the same as the physical label. This electronic label is the name of the volume, and it will be displayed when you search the contents of your computer. 6/7/2014 ArabOU - M150 - AbuNawaf 18 18

  19. Computer Hardware and Software components work together in order to execute computer program. Hardware: describes the physical parts of computer that can be touched. Software:describes the information or the programming the computer uses, you can't touch it. a software program or set of instructions programmed on a hardware device (usually in the ROM) It provides the necessary instructions for how the device communicates with the other computer hardware can be thought of as "semi-permanent" since it remains the same unless it is updated. Hardware, software and computer systems Software vs. hardware 6/7/2014 ArabOU - M150 - AbuNawaf 19 19

  20. Although Hardware and Software are different in nature, there are related. A solution to a computer problem can be implemented using either Hardware or Software. Hardware uses several tangible electronic circuits. Software uses instructions to use same circuits. Software vs. hardware 6/7/2014 ArabOU - M150 - AbuNawaf 20 20

  21. The Central Processing Unit: (CPU also called processor) is the part of the computer that executes program instructions. It consists of two parts: 1. The Arithmetic and Logic Unit (ALU) is where all calculations and logical operations are performed. a- Arithmetic operations involve addition, subtraction, multiplication, and division. b- Logic operations basically consist of comparing or combining two values: All ALUs can compare >, <, and =. Some ALUs can also compare >=, <=, and <>. Comparisons can be combined using the logical operations NOT, AND and OR. Truth tables are used to formally define these logical operations. 2. The Control Unit (CU): The control unit interprets program instructions. The control unit communicates with main memory and with input and output device controllers. The control unit directs the ALU to execute program instructions. The resources of a computer, and how they are managed The heart of the computer – the CPU 6/7/2014 ArabOU - M150 - AbuNawaf 21 21

  22. The CPURegisters : are high-speed storage locations within the CPU, used for specific tasks: Memory Data Register(MDR) is used to hold data that are being transferred to or from primary storage. Memory Address Register (MAR) indicates the location of the data to be stored or retrieved from primary storage. Instruction Register (IR) holds the instruction being executed. Program Counter (PC) holds the primary storage address of the next instruction to be executed. The address held in the PC ,instruction cycle insures sequential execution of instructions. Jumps to another part of the program are achieved by instructions, which reset the contents of the program counter. The heart of the computer – the CPU..continue 6/7/2014 ArabOU - M150 - AbuNawaf 22 22

  23. Accumulator (AC) holds the results of ALU operations. Program Status Register (PS) contains binary flags that signal the results of the previous operation. For example the carry bit will be set to 1 if the last arithmetic operation lost a carry bit, and to 0 otherwise. Other condition codes indicate whether the last result was negative, zero or overflowed. General-purpose registers are used for different purposes. The first three registers are used by the control unit and are not accessible to the programmer. The arrangement of registers define the processor architecture. The heart of the computer – the CPU..continue 6/7/2014 ArabOU - M150 - AbuNawaf 23 23

  24. (also called primary storage, internal storage, or main memory). Memory is the part of the computer that holds data for processing, programs, and information waiting to be output to secondary storage. There are three main characteristics of memories: The capacity of the memory varies in different computers and is measured in bytes. A byteconsists of 8 binary digits called bits. Each bit can represent binary 0 or binary 1. Each byte represents one character in memory. There are four commonly used units of memory capacity: More about the CPU and main memory 6/7/2014 ArabOU - M150 - AbuNawaf 24 24

  25. There are two types of memory chips: Random access memory (RAM): Data and programs must be loaded from external storage (such as disk) into RAM before it can be used by the processor. RAM is volatile (temporary). Read only memory (ROM): chips have programs built into them at the factory and cannot be changed by the user, thus they are not volatile. programmable ROMs (PROM) that can be programmed by the user using special devices to save his own information. ROM typically contains special instructions to start up the computer, give keyboard keys their special control capabilities and put characters on the screen. More about the CPU and main memory.. 6/7/2014 ArabOU- M150 - AbuNawaf 25

  26. Memory hierarchy: there is a memory hierarchy consisting of primary memory (CPU internal registers, cache memory, main memory) and secondary memory (external devices such as disks) Cache memory: is a high-speed expensive RAM memory used to store copies of the most frequently accessed information in main memory. Virtual memory: Virtual memory is a memory system used to increase the effective size of the computers physical main memory. More about the CPU and main memory.. 6/7/2014 ArabOU- M150 - AbuNawaf 26

  27. We mentioned before that the main memory is volatile (temporary). If the power is turned off program and data disappear. External storage is nonvolatile (permanent). External storage also has much more capacity than the primary memory. There are two approaches to external storage: sequential access and direct access. The most widely used external storage media are -- floppy disks, hard disks, optical disks and magnetic tapes. Disks are direct access storage media, while tapes are sequential access storage media. Peripheral devices 6/7/2014 ArabOU- M150 - AbuNawaf 27

  28. Is the most important system software component. It interacts between the application software and the computer and manages the computer’s internal resources. Within the OS, besides the kernel, there is a group of other programs called utility programs, that perform common tasks, such as formatting disks, copy files from other disks, backup disks, remove and rename files, and others. Mainframes and minicomputers have powerful OS, including virtual memory, multiprogramming and multiprocessing, where many users can run different programs at the same time. Microcomputer OS focus on a single user. The most important operating systems are: DOS, Microsoft Windows, Unix, Linux and MAC. The Operating Systems (OS) 6/7/2014 ArabOU- M150 - AbuNawaf 28

  29. The Operating system has the following functions; Provision of user interface Management of the memory Coordination and control of peripheral devices. Scheduling access for the processor Interface between Hardware and computer applications. Provide basic utilities (disk formatting, file management, etc….). The bootstrap loader: is a program that is stored permanently in the computer’s electronic circuitry in ROM. This process is called booting. The Operating Systems (OS) .. continue 6/7/2014 ArabOU- M150 - AbuNawaf 29

  30. Accessing data Database • A database (db) is a collection of data stored in a computer system according to a set of rules, and organised to facilitate access involving complex searches and selection. • The primary emphasis of database applications is on making the data persistent, and structuring it so as to minimise redundancy, avoid inconsistency & maximise the usefulness of the data for the purposes of access and updating. • A query (request to db) is used to get specific information from the db. The response to the query ideally extracts from the database all the relevant information. So a database is part of an information system. 6/7/2014 ArabOU - M150 - AbuNawaf 30 30

  31. Database .. continue Table ??? Row ??? Field ??? Key ??? What is the engine size of Tom Cobbley’s car? (Hint: use the two tables in combination) 6/7/2014 ArabOU - M150 - AbuNawaf 31 31

  32. Database .. continue • Databases consist of many tables holding vast amounts of data, designed with great care in order to be able to provide answers to (possibly complex) queries. • A typical industrial database system will consist of: • A collection of tables • Data (called metadata) which describes the tables (what each column in a table means, and how many tables there are in a database….) • Facilities for backing up the tables. • Facilities for ensuring security (credit card details) • A query facility. 6/7/2014 ArabOU - M150 - AbuNawaf 32 32

  33. Object Database • Object database may contain video, voice and music along with more traditional forms of data. • A data object (sound, image, video) may be contained within a database as ‘an object in a box’. The box has a name and the database can access the object using this name. • An object stored in this way is called a BLOB (binary large object). There are facilities for the storage and retrieval of these data types but the weakness of this approach is that you can NOT query the content of a BLOB (the BLOB has NO structure to it). • Solution: Metadata 6/7/2014 ArabOU - M150 - AbuNawaf 33 33

  34. Metadata • In order to describe anything other than the simplest of data, it is necessary to provide some form of explanatory data (i.e. metadata) about the data. Email headers are good examples. • Web pages have a rudimentary form of metadata in the form of keywords that can be used by search engines to locate web pages of a particular topic. • Each item in the <HEAD> section of an HTML document is an example of metadata. It is not part of the content of the document; rather, it says something about the content. 6/7/2014 ArabOU - M150 - AbuNawaf 34 34

  35. Metadata .. continue • An adequate collection of metadata (hooks or pointers) will identify the various features of multimedia databases to make it searchable. • Each still picture, audio clip and video will have a number of associated items of metadata. • MPEG-7 provided a visual descriptors (colour, texture, shape, position, motion and face recognition) and audio descriptors (key, mood, tempo and tempo changes). Example: This is a scene with a barking brown dog on the left and a blue ball on the right, with the sound of passing cars in the background. 6/7/2014 ArabOU - M150 - AbuNawaf 35 35

  36. During the program execution the CPU do the following steps: Get an instruction from the program. Find and transfer any data necessary to perform instruction. Carry out the instruction. The process of locating, transferring and carrying out a single instruction during execution is called fetch/execute cycle. Running a program The fetch/execute cycle 6/7/2014 ArabOU- M150 - AbuNawaf 36

  37. During each cycle the CPU must: Locate the next instructionin the program which is stored in the main memory (first one is used if the execution has just started). Transfer the instructionin to the processor by putting it in a register. Decode the instruction. Locate any data located in the main memorywhich refers to the instruction. Do the processing. Place the result in an appropriate register. If needed move result back to the main memory to be used later. Increment the program counter by 1. The fetch/execute cycle .. continue 6/7/2014 ArabOU- M150 - AbuNawaf 37

  38. Five Generations of Programming Languages GENERATION NAME SAMPLE STATEMENT First Machine 10010001 Second Assembly ADD A, B JMP L Third Procedural and structural Overtime:= 5 0; Fourth Object oriented FIND NAME "JONES“ Fifth Natural IF patient is dizzy, THEN check temperature and blood pressure Computer professionals talk about levels or generations of program­ming languages, ranging from ‘low’ to ‘high.’ Programming languages are called lower level when they are closer to the language the computer itself uses. The computer understands the 0s and 1s that make up bits and bytes. Programming languages are called higher level when they are closer to the language humans use that is, for English speakers, more like English. Types of programming languages Low-level languages 6/7/2014 ArabOU- M150 - AbuNawaf 38

  39. We mentioned earlier that a byte is made up of bits, consisting of 1s and 0s. These 1s and 0s may correspond to electricity’s being on or off in the computer. They may also correspond to a magnetic charge’s being present or absent on storage media such as disk or tape. Data represented in 1s and 0s is said to be written in machine language. To see how hard this is to understand, imagine if you had to code this : 111100100111001111010010000100000111000000101011 Machine languages also vary according to computer design - another characteristic that makes them hard to work with Machine Language: the First Generation 6/7/2014 ArabOU- M150 - AbuNawaf 39

  40. Assembly languages have a clear advantage over the 1s and 0s of machine language because they use abbreviations or mnemonics. These are easier for human beings to remember. The machine language code we gave earlier could be expressed in assembly language as: ADD A, B JMP L Assembly language is also considered low-level. Assembly languages also vary from computer to computer. With the third generation, we advance to high-level languages, many of which are considered portable languages. That is, they can be run on more than one kind of com­puter—they are “portable” from one machine to another. Assembly Language: the Second Generation 6/7/2014 ArabOU- M150 - AbuNawaf 40

  41. People are able to understand languages that are more like their own (e.g., English) than machine languages or assembly languages. These more English-like programming languages are called “high-level” languages. However, most people still require some training in order to use higher-level languages. This is particularly true of procedural languages. Procedural languages are programming languages with names like BASIC, Pascal, C, COBOL, and FORTRAN. They are called “procedural” because they are designed to express the logic—the procedures—that can solve general problems. For a procedural language to work on a computer, it must be translated into machine language Depending on the language, this translation is performed by either a compiler or an interpreter. High-level languages (Third Generation) 6/7/2014 ArabOU- M150 - AbuNawaf 41

  42. A compilerconverts the programmer’s procedural language program, called the source code; into a machine language code, called the object code. An interpreterconverts the procedural language one statement at a time into machine code just before it is to be executed. No object code is saved. What is the difference between using a compiler and using an interpreter? When a program is run, the compiler requires two steps. The first step is to convert the entire program’s source code to object code. The second step is to run the object code. The interpreter, in contrast, converts and runs the program one line at a time. The advantage of a compiler language is that once the object code has been obtained, the program executes faster. The advantage of an interpreter language is that programs are easier to develop. High-level languages (Third Generation) 6/7/2014 ArabOU- M150 - AbuNawaf 42

  43. Third-generation languages are valuable, but they require training in program­ming. Object-oriented languages, also known as very high-level languages, require little special training on the part of the user. Unlike general-purpose languages, object-oriented languages are designed to solve specific problems. Some of these fourth-generation languages are used for very specific applications. Many consider Lotus 1-2-3 and dBASE to be flexible fourth-generation languages. Query languages: Query languages enable nonprogrammers to use certain easily understood commands to search and generate reports from a database. An example is the commands used on an airline reservations system Problem-Oriented Language: The fourth Generation 6/7/2014 ArabOU- M150 - AbuNawaf 43

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