- Ads:  Easy to write  Easy to understand  Known the processing data in CPU  Prog writing is shortset - Dis:  Must be complier  The time of running prog is longer than machine language 3. High level language - HLL was developed in order to further easy the work of programmers by making the programming language more procedure oriented - Features:  The statements of HLL are closer to natural english or other natural language  A HLL source program must be translated into machine code by means of a compiler or an interpreter - Ads:  Easy to wirte  Easy to understand  May be used for everybody  Closed to natural languages english language - Dis:  Must be interpreter by compiler or an interpreter before processing by the computer  The prog is long  The time to run the prog is longer than low level language Question 2. Some High Level Languages (HLL)? 1. COBOL: Common Business Oriented Language - COBOL is an exetensively used HLL and since around 1960 several versions have appeared - The original intention was that COBOL should be capable of being compiled and run on any model of computer - COBOL is now employed for many business data processing applications, and so a brief explaination of its structure follows - A COBOL program consists of 4 divisions:  Identifycation division this identifies the prog  Enviroment division specifies the computer to be used for compiling and processing  Data division specifies the format and relates to these to the names used in the procedure division  Procedure division comprises the statements in the source program, this is the main part of a COBOL program 2. BASIC: Beginners ALL purpose Symbolic Instruction Code - BASIC is a straightforward HLL intended for use in a time-sharing environment in this respect it is particularly beneficial in educational institutions - One of the difficulties with BASIC is the welter of dialects currently in use Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m - Essentially BASIC consists of statements made up of verbs & variables. The verbs are similar to those in COBOL but there is a large to them that in effect become the addresses of their locations in the main store - A variable name must be unique and generally consists of one or a few alphabetic characters, purhaps followed by a digit 3. PASCAL: named after the famous 17 th century French mathematician - It was expressly designed as a language to make programming more systematic and discriplired and in these respects lends itself to structured programming - It is however more difficult to learn than are COBOLS BASIC and so is unliked to be accepted as a language for microcomputers are geared to BASIC only Question 3. Operating Systeim? - Concept of OS:  An OS consists of a suite of programs, one of which, the master, kernel or exeactive program, remains resident in the main store. This program controls the other OS programs in th suites and between them they controls the application programs  Often the operating system includes various application packages among its suit of programs. Ex of such software include: word processing, electronic mail, networking, speadsheet, graphics and file handling - Function of OS  Pricrity assignment: Jobs waiting execution are scheduled according to either a predetermined or a dynamic assignments plan  Control of multiprogramming Control of accomplish multiprogramming an “executive” or “supervisor” program is employed to control the application programs  Communication Control of data transmission between terminals and the computer, and computer to computer  Database Control of DBMS  Software control Control of assemblers, compilers, utility software, and subroutines so that these are imediately available when required  Spooling The control of input/output peripherals in order to achieve their best utilisation  Dynamic allocation Of main and backing storage, including virtual storage  Operating allocation Via the console printer or VDU  Debugging and editing new programs In confunction with the compiler, and passing error msgs to the user  Operation log Maintaince of details of all jobs carried out by the computer Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m  Application package control Especially with microcomputers, as describe above Chapter 6: TRANSLATORS. Question 1. Translators? 1. Assemblers  Def: A program that translates assembly language into machine code. Dos machine instruction is generated for each source instruction - The resulting program ran only be executed when the assembly process is completed  Operation: - Translates mnemonic operation codes into machine code & symbolic address into machine address - Includes the neressary linkages for closed subroutines and inserts appropriate machine code for macros - Allocates area of storage - Detects and indicates valid source language instruction - Procedures the object program on tape or disk required - The lesting may also include error codes if appropriate. To illustrate the methods used just think about an assembly program. We must first look at the directives  A directive is used to control the assembly process, it is not asembled but is obeyed by the assembler when it is encouteded, e.g ”END”, is sometimes called a pseudo- operation code on pseudo-opcode 2. Interpreter A program which translates and executes each source statement in logical sequence as the program one instruction at a time, completely translating and executing each instruction before it goes onto the next - Interpreter, which deals with the source program one instruction at a time, completely translating and executing each instruction before it goes onto the next - Interpreter seldom produce object code but call upon inbuilt routines instead - Some intermediate code is usually produced tempororily - If an interpreter is used, the source program will be translated every time the program is executed - Interpreters are widely used, particular for the programming language Basic on small computers  Interpriter are used for such things as: - Handling user commands in an interactive sys - Debugging programs as they run - Handling software produced for or by a different computer 3. Compilers: A program that translates HLL into a machine orientated language, often the machine code. Many machine instructions are generated for each source statement - The compiler: Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m  Translates the source program statements into machine code  Includes linkage for closed subroutines  Allcocates areas of main storage  Generates the object program on cards, tape and disc as required  Produces a printed listing of the source and objected programs when required  Tabulates a lish of errors found during compilation - Compilers are commonly used for the translation of HLL program - Compiler translates the whole of the HLL source program into a machine code object program prior to the program being loaded into main memory and executed - If a compiler is used, the same program need only be translated once  Stages of compilation  lexical analysis  systatical analysis  code generation Chapter 7: SOFTWARE. Question 1. Application software? - Application software comprises the programs that are written specifically to achieve resulting appertaining to the company’s activities - Application software comes from two source  They produce by themselves  Buy from an external agency 1. Ads and dis of using application packages in house  Ads - The requirements of the application are more easily met - There is more control in testing and debugging - The more control over the usage and support obtained  Dis - There is a waiting period before the application can be implemented - Development cost is higher than buying a package 2. Ads and dis of using application package  Ads: - The packages can be used immediately - Documentation is generally good - It can be used on a varisty of machines - It is cheaper as the costs of the packages are shared between many users - Comprehensive on line help information and guided tutorials available - Easily remembered command syntax - Can be used in confunction with other software in an integrated fashion  Dis: - Modifications may be difficult for some applications - Package may be two generalized to suit user needs - Some features purchased may not be required Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m - Support given depends on stability and professionalison of the vendor - User are required to comply with the owner’s regulations Question 2. Utility software? - Certain processing is common to a high proportion of computer users, and so utility software has been created to cater for this need - Utility software is intended to be sufficiently flexible to meet most user’s requirements and is tailored to meet their precise needs by means of parameter entered prior to use - Some of the utility programs described below may be incorporated into the OS that is used with a particular computer  File conversion: this convers the transference of data from any medium to any other  File copying: an exact copy of a data set is made on to another lot for the same type of storage medium  File reorganisation: direct access, files over flow records are stored in designed blocked, this is acceptable up to a point but from time it si necessary to reorganise the file so as to remove the overflow  File maintenance(amendment): this procedure involves the straightforward insertion and deletion of records into or form sequential files  Sorting: is frequently necessary in order to arrange a set of records into a certain sequence based on their key values  Dumping routines: a dump routine is used in confunction with a restfirt program  House keeping operations: there are programs or parts of a programs not directly concerned with the solution of the problem in hand  Trace routines: these entails, the dumping, display or printing of th program or other contents of the main store during program testing to facilitate error detection - Utilitys are commonly used to perform these functions:  Copying of files  Sorting of data  Merging of files  Data recovery  Reformating of records by reamanging their fields  File reorganization  Reporting of sys status and usages Question 3. System software? There are three main types of memory placement policy: - First fit - Best fit - Worst fit 1. First fit policy, an incoming job is placed in the first available free space large enough to fit it. This allows the placement decision to be made quickly 2. Best fit policy, an incoming job is placed in the free space in which it fits most tightly Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m 3. Worst fit policy, an incoming job is placed in the largest possible hole of free space Question 4. Types of scheduling? - Scheduling of job is also an important part of any OS. It involves keeping track of and deciding which job is to be executed - Types of scheduling  Deadline scheduling  First in first out scheduling(FIFO)  Round robin scheduling  Shortest job first(STF) scheduling  Shortest remaining time scheduling(SRT) - More details about types of scheduling  In deadline scheduling certains are scheduled to be completed by a specifir time or deadline. Deadline scheduling can be very complex requiring substantial overhead in resource management  FIFO scheduling: processes are dispatched according to their arrival time in the ready queue. This type of  Round robin scheduling is similar to FIFO scheduling but the difference lies in that each job is given a slice of CPU time  SJF scheduling: shorter jobs are more favoured than longer one. SJF selects job that ensures the next jobs will complete & leave the sys as soon as possible  SRT scheduling: the job will the smallest estimated remaining run time is executed first. In SRT, a running job may be replaced by a new job with a shorter estimated run time Chapter 8: MEMORY MANAGEMENT. Question 1. Virtual Storage System? - Instructions and data not currently needed might even be stored on the disk and thus free up a portion memory - Virtual storage systems have evolved to meet these needs. Virtual storage systems allow programs to be as large as necessary, even larger that the physical storage capacity of the computer - Translating the user’s view of the program into the physical reality of computer storage is one of the major task performed by virtual memory OS like IBM’s MVS and digital VMS - Virtual storage system included non paged systems Paged systems Chapter 9: NETWORKING. Question 1. Types of network layout? Network topology is the name given to the various types of network layout 1. Start network(or centralised network) - This network all communications go through a central node Node A Node D Central(Hub) active Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Passtive Node C Node B - The centra of star network is the hub which performs the function of routing msgs and data within the network - The hub manages & senvices all incoming and outgoing communication traffic. It’s also provide info services from a large central data bases 2. Mesh network (or distributed network) - This network may be fully connected or partially connected A E B D C - Data can get from one node to another node via different route - Multi point to point 3. Ring network( or loop network) A B D C - Work stations connect to the ring - More cabling requiring than BUS - The connectors used with a lot of problem - Cable is used UTP, STP 4. Bus network( or multidrop network) A B - All workstations are connected the same cable segment - Commonly used for implomenting ethenet at 10 mbps(Mb/s) - The cable is terminalled at each end - Writing is normally store point to point - A faulty cable or work station will take the entire LAN down Question 2. Network control? Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m 1. Modems(modulation demodulation) A telephone line B Modem modem Digital signal analog signal OR Data transmission Using a Modem - To communicate between computers via telephone line, there is a need to convert signals from the computer into a form suitable for transmission over the telephone line or convert from digital signals into analogue signals, and convert back from analogue signals to digital signals - From source: digitals signals are converted into analogue signals(modulation) - At the received end analogue signals are converted back into digital signals (demodulation) - A device to handle modulation, demodulation process is called Modem 2. Bandwidth and Fibre Opties The major benefits of fibre opties are: - Fibre optic cables are much lighter and smaller in size - Greatly increased speed in data transmission - Greatly reliability - Greater secerity as lines can not be tapped 3. Transmission a. Simplex transmission This method allows for transmission in one direction only b. Half duplex transmission This method means that’s data can be transmitted in both directions, but is only on direction at a time c. Full duplex trasmission This method of transimission allows for transmission in both directions simultaneously * Two modes of transmission are used when transmitting data over communication lines. They are  asynchrorous  synchronous Asynchronous: - One character at a time is transmitted or received - Each character is preceded by a start bit and a stop bit  The start bit is used to indicate or character is being sent  The stop bit is used to indicate the end of the character - Asynchronous transmission is used for low speed devices Direction of transmission Com pute Com pute Mod Mod Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m S S S S T T T T A 11000001 O 1111111 A 11000010 O R P R P T T Synchronous: - The speed of transmission is much faster - Transmission groups of character can be send down the line without the start and stop bits Direction of transmission 000111000001011100000011 Question 3. LAN_Local Area Networks?  Def: A LAN is a communication network in that connects office equipment to provide a variety of data communication service which features high transmission rates and low error rates  Characteristics: - Utilisation of some type of switching topology - Locality restricted to a few miles or in the same bulding - Proprietorship by a single organisation  Features: - LAN is after used in offices & it connects of fire equipment to provide a variety of data communication. Service with light transmission rate and low errors rate - The majorities of LANs are connected by coxial cable, and the protocol(rule for communication) is very simple  Three other important aspects of LANs: - Acess method (protocol) Central control CSMA_CD Empty slot access Token access/token passing  LAN transmission modes: There are 2 main types of LAN transmission modes a. Baseband transmission: is essentially & binary method, each bit being represented by one of two states of an electric pulse passing through the network. Baseband is nevertheless suitable for most LANs, and is the mode employed by Ethernet and Cambridge Ring network b. Broadband transmission: the data is modulates into a carrier wave. Broadband transmission has a much greater band width than baseband, it can transmit sth like ten times as much in a given time  LAN is one of the distributed processing designs - LAN are considered loosely coupled system processors are located in separate machines and communicate at relatively low speeds - LAN is the means by which distribution takes places, regardless of what are distributed Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Chapter 10: DATA COMMUNICATIONS. Question 1. Write a short note of? 1. Communication is an extensive subject in its own right, encompassing not only data transmission but also sound and video transmission via telephone lines, radio links and satellite links. 2. Multiplexing is a means of combining together data from several sources so that it can be transmitted along one comminication line 3. Front – end processing: A front – end processor is usually a minicomputer or a microcomputer interposed between the main computer and the multiplexor Its purpose is to relieve the host computer from the bunden of communications housekeeping 4. Concentrators are device used to gather the bit from each terminal or group of terminal and hold them on buffer store unit until there are sufficient to justify forward transmission 5. Protocol is an “agreement” where by devices can communicate is a fully understand manner 6. Multidrop line<multipoint line> has several terminals on concentrator attached to it 7. Distributed data processing sys is one of which interconnected points at which processing power and storage capacity are availble Question 2. Fibre Optics?  Fibre optics is that data and other information is transmitted in the form of light through very fine glass fibres  Ads: - High bandwidth eg data transmission capacity - Low cross – talk eg interference between adjacent fibres - Low attenuation eg loss of signal strength - Freedom from interference from external electrical and electromagnetic equipment - High reliability - Safe because no heat, sparks or electrical voltages are created - Economic because glass is loss expensive than copper Chapter 11: DISTRIBUTED PROCESSING. Question 1. Client/ Server Model? - It’s common way to employ distributed processing that is client/server architecture which splits into components - Server store & main palates the actual data & provide secenity, losting function transaction logging recovery capabilities - Client/ server model seems like PC lan each server support more users - Data request in form of SQL(structure quenf language) command travel across the network from client to server Client Server Database Request Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m Click to buy NOW! P D F - X C h a n g e V i e w e r w w w . d o c u - t r a c k . c o m . remaining time scheduling(SRT) - More details about types of scheduling  In deadline scheduling certains are scheduled to be completed by a specifir time or deadline. Deadline scheduling. and deciding which job is to be executed - Types of scheduling  Deadline scheduling  First in first out scheduling(FIFO)  Round robin scheduling  Shortest job first(STF) scheduling . mnemonic operation codes into machine code & symbolic address into machine address - Includes the neressary linkages for closed subroutines and inserts appropriate machine code for macros -