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Japan information technology foundation (2.Computer Systems (2.1 Hardware,…

- - - - Conversion of Binary or Hexadecimal Numbers into Decimal Numbers
        (12A)16 = 1 × 162 + 2 × 161 + A × 160 = 256 + 32 + 10 = (298)10
        (1100100)2 = 1 × 2(6) + 1 × 2(5) + 0 × 2(4) + 0 × 2(3) + 1 × 2(2) + 0 × 2(1) + 0 × 2(0)
      - Conversion of Decimal Integers to Binary Numbers
        (59)10 = 32 + 16 + 8 + 2 + 1 = 2(5) + 2(4) + 2(3) + 2(1) + 2(0 )
        = 1 × 2(5) + 1 × 2(4) + 1 × 2(3) + 0 × 2(2) + 1 × 2(1) + 1 × 2(0)
        =(1 1 1 0 1 1)2
      - Conversion of Decimal Numbers into Binary Numbers
        (0.59375)10 = 0.5 + 0.0625 + 0.03125 = 2(-1) + 2(-4) + 2(-5)
        = 1 × 2(-1) + 0 × 2(-2) + 0 × 2(-3) + 1 × 2(-4) + 1 × 2(-5) = (0.1 0 0 1 1)2
      - Conversion between Hexadecimal and Binary Numbers
        FROM BINARY TO HEXADECIMAL. We can use the fact that each digit of a hexadecimal number corresponds to 4 bits in binary.(10110111100100)2 → (10 1101 1110 0100)2 → (2DE4)16
        FROM HEXADECIMAL TO BINARY (2DE4)16 → (0010 1101 1110 0100)2
      - Conversion between Hexadecimal Fractions and Decimal Fractions
        FROM DECIMAL TO HEXADECIMAL FRACTION (0.71875)10 → (0. 10111)2 → (0.B8)16
        FROM HEXADECIMAL TO DECIMAL6 (0.B8)16 → (0.10111000)2 → 0.71875 = (0. 1011 1000)2 0 = (0.10111000)2 = 2-1 + 2-3 + 2-4 + 2-5 = (0.71875)10
    - - Decimal Number Representation In the zoned decimal format, each digit of the given decimal number is represented by 8 bits,
        and the highest 4 bits of the last digit are used for the sign information.7 The numeral bits of each byte contain the corresponding numerical value in binary
    - - Character Representations
        
        EBCDIC Computer code defined by IBM for general purpose computers 8 bits represent one character.
        
        ASCII 7-bit code established by ANSI (American National Standards Institute) Used in PCs, etc.
        
        ISO646 published as a recommendation by the International Organization for Standardization (ISO), based on ASCII 7-bit code for information exchange
        
        Unicode An industry standard allowing computers to consistently represent characters used in most of the countries Every character is represented with 2 bytes
        
        EUC 2-byte and 1-byte characters can be used together on UNIX (extended UNIX code). Chinese and Hangul characters are also handled.
      - Image and Sound Representations
        
        Still images GIF , JPEG Moving Pictures MPEG Sound PCM MIDI
    - - Shift Operations A shift operation is the operation of shifting (moving) a bit string to the right or to the left.
        Shift methods can be classified as shown below.
      - Errors Rounding errors, Cancellation of significant digits, Loss of trailing digits
  - - - Definitions of Logical Operations
        
        Logical sum (OR) A + B
        
        Logical negation (NOT) A-
        
        Logical product (AND) A ⋅ B
        
        Exclusive logical sum (EOR, XOR) A ⊕ B
      - Truth Tables / Logical Operations
      - De Morgan's Theorem
        
        Negation of logical sum: (-A + -B) = -A ⋅ -B . Negation of logical product: (-A ⋅ -B) = -A + -B
      - Adder
        
        Half adder (HA)
        
        Full adder (FA)
    - - To define the grammar of a programming language (syntax definition), expressions free from any ambiguity are required. To express such a grammar, BNF (Backus-Naur Form) is often used
        
        Basic Forms of BNF Sequence <x>::=<a><b> Repetition <x>::=<a>… Selection <x>::=<a | b>
        
        Terminal and Non-Terminal Symbols <y>::=<a><x> , <x>::=<b><c>
        
        Examples of BNF <floating-point constant>::=[<sign>]<radix constant>[<exponent>] | [<sign>]<numeric string><exponent>
    - - For example, X = A + B C means “Calculate the product of B and C, add A, and then move the result to X.” This is expressed by extracting the underlined parts as follows:XABC+=
        
        Conversion of Mathematical Formula to Reverse Polish
        Notation For example, let us convert “ e = a − b ÷ (c + d ) ” into Reverse Polish Notation. eR = Æ eaQ − = Æ eabP ÷− = Æ eabcd + ÷ − =
        
        Conversion from Reverse Polish Notation into
        Mathematical Formula For example, consider the formula in Reverse Polish Notation “ eabcd + ÷− = .” This is converted as follows: e = a − b ÷ (c + d)
        
        Polish Notation In Polish Notation, “ a + b ” is expressed as “ + ab ”, for instance. e = a − b ÷ (c + d) Æ = e − a ÷ b + cd
  - - - 1-Dimensional Arrays Index Array T 1 2 3 4 … 25 26 a b c d … y z
      - 2-Dimensional Arrays Column 1 Column 2 Column 3 Column 4
        Row 1 a (1,1) a (1,2) a (1,3) a (1,4)
        Row 2 a (2,1) a (2,2) a (2,3) a (2,4)
        Row 3 a (3,1) a (3,2) a (3,3) a (3,4)
      - Row-Directional Storage and Column-Directional
        Storage
    - - Structures of List A list is a data structure in which the elements are connected by pointers. A pointer isinformation indicating the storage location (address) of the next element. Each element is connected by a pointer, so the elements need not be placed in order.
      - Basic Operations of List
        
        Insert
        
        Delete
    - - Basic Operations of Stack A stack is a data structure of LIFO (Last-In First-Out)
      - Use of Stack
      - Implementation of Stack using List Using the structure of a list, we can implement a stack. In case of the following list, an element can be added to or deleted from the top of the list
        
        Insert to the list
        
        Delete from the list
    - - Operations of Queue A queue is of the type referred to as FIFO (First-In First-Out)
      - Implementation of Queue using List
        
        Insert into the list
        
        Delete from the list
      - Examples of Queues In multiple programming, programs waiting to be executed are placed into the queue for execution as long as their priorities are equal, and they wait for the CPU to be available. In online transaction45 processing, messages (electronic texts) are entered into a queue and processed in the order of entrance
    - - Binary Trees and Complete Binary Trees
      - Binary Search Trees
      - Heaps The heap which meets the former condition is called the max-heap, and the min-heap for the latter condition.
    - - Chain Method (Open Hash Method)
      - Open Address Method (Closed Hash Method)
    - - 1.4.1 Search Algorithms
        
        Linear Search
        
        Binary Search
        
        First comparison
        
        Second comparison
        
        Third comparison
        
        Fourth comparison
        
        Comparison between Linear and Binary Search
        Mean number of comparisons for linear search = N/2
        Maximum number of comparisons for linear search = N
        Mean number of comparisons for binary search = [log2N]
        Maximum number of comparisons for binary search = average number of comparisons for binary search + 1
      - 1.4.2 Sorting Algorithms
        
        Bubble Sort
        
        Selection Sort
        
        Insertion Sort
        
        Quick Sort
        
        Merge Sort
        
        Shell Sort
        
        Heap Sort A heap is a binary tree in which every subtree has the property that a parent has a value larger than its children. If the root element is picked, we can obtain the maximum value while the remaining elements can be re-structured to form a heap.
      - 1.4.3 String Search Algorithms
        
        Brute-Force Search Method
        
        Boyer-Moore Method (BM Method) This is a method that takes the contents of the pattern string into account to eliminate waste. If the pattern and a string of the text do not match up, the number of characters that can be skipped depends on the right-end character of the search range of the text being compared.
      - 1.4.4 Graph Algorithms A graph consists of nodes and edges. A node is a vertex that forms the graph whereas an edge is a segment connecting a point to a point. Below is an example of a graph.
        
        Breadth-First Order
        
        Depth-First Order
- - - - ROM (Read-Only Memory)
      - RAM (Random Access Memory)
    - - Configuration of Computer
      - Address Modification and Addressing Methods Address modification is a function that obtains the value of the address actually accessed based on the address specified by the instruction.
        
        Direct addressing method
        
        Indirect addressing method
        
        Indexed addressing method (index modification)
        
        Base addressing method
        
        Immediate value addressing method This is the method where the address of the instruction stores the data subject to processing, not an address.
      - RISC and CISC
        
        RISC (Reduced Instruction Set Computer) These computers have only a set of simple, frequently used instructions integrated onto a single VLSI (very large scale integration) chip in order to achieve high performance through improved machine cycles (operation speed) and a reduction in instruction processing time.
        
        CISC (Complex Instruction Set Computer) These computers have complex instructions integrated onto a single VLSI ship in order to achieve high overall performance. Most general-purpose computers are CISCs.
      - Pipeline Control .Pipeline control is a technology to reduce the instruction execution time of the CPU.
    - - Memory Hierarchy Memory hierarchy is a hierarchical representation of the relationship between the access speed
        and capacity of various types of memory.
      - Cache Memory (High-Speed Buffer Memory) Cache memory is high-speed, small-capacity memory that is placed between the CPU or
        registers and the main memory.
      - Interleaving (Memory Interleaving) The main memory is divided into multiple units called banks, and addresses are assigned across the banks.
    - - Capacity Calculation The record format of a magnetic tape is shown below. As we can see in this figure, in order to record one block, we needs to include an IBG (Inter-block gap) which is an area to identify the block and contains a special code. A magnetic tape reader reads data in block units, so this area is crucial even in identifying the end of each block.
      - Performance Calculation The running speed of the tape is constant when reading or writing data. In theory, the tape begins to accelerate in the middle of IBG and starts to read and write when a constant speed is achieved. When another IBG is found, the tape decelerates and stops in the middle of IBG.
    - - Capacity Calculation Just as on a magnetic tape, data is recorded in blocks on a hard disk. However, if a block cannot fit into a track, it cannot be recorded.
      - Performance Calculation The access time of a hard disk is calculated as follows: Access time = waiting time + data transfer time = (seek time + latency time) + data transfer time
      - Capacity Calculation of Sector-based Hard Disk The term sector refers to the way a magnetic medium is partitioned on floppy disks or hard disks.
    - - Terms Related to Performance Waiting time = Seek time + Latency time (or Search time)
      - RAID (Redundant Array of Independent Disks) RAID describes auxiliary storage in which multiple hard disks are placed in parallel and are controlled as if they were one disk unit so that the input/output speed can be improved and/or reliability can be enhanced.
    - - Auxiliary Storage
      - Input and Output Units Input units include keyboards, image scanners, tablets, pointing devices, etc. Output units include displays, printers, etc.
    - - Data Transfer Methods
      - Types of Input and Output Interfaces
  - - - Configuration of OS
      - Objectives of OS
    - - Tasks and JobsA unit of processing from the perspective of the user (a single program or a set of programs executed consecutively) is called a job. In contrast, a unit of internal processing executed underthe OS is called a task. “Task” refers to a processing unit that subdivides a program process.
      - Control of Task Execution Task management generates tasks required in response to a command and monitors the execution process.
      - Interruption Interruption refers to temporary suspension of a program currently being executed for any reason and transferring control to the OS to execute some necessary processing program.
    - - Access Methods Access methods include sequential access, direct access, and dynamic access, which is a combination of the first two.
      - File Organization File organization methods include sequential organization, direct organization, indexed organization, and partitioned organization
      - Hierarchical File Systems
        
        Directories and files
    - - Real Memory System
        
        Partitioned method When a program is placed in the main memory, the main memory is partitioned into several partitions, into which the program is loaded
        
        Swapping (roll-in / roll-out) Swapping refers to execution as the program keeps switching back and forth between the main memory and auxiliary storage.
        
        Relocation (Relocatable) Relocation refers to the function wherein a program already assigned to a certain area is re-stored in another location. A program whose structure allows it to be relocated is called a relocatable program.
        
        Overlay method The physical limitations of the main memory can be eliminated; that is, programs are divided into segment units, and only the necessary segments75 are loaded into the main memory to be executed.
      - Virtual Memory Virtual memory provides a large capacity of storage space regardless of the size of the main memory.
      - Paging Algorithms If a page necessary for processing is not found in the real memory, an interruption called a page fault occurs, and the page is read into the real memory from virtual memory
  - - - Overview of Client Server System CSS is configured with computers with roles called clients and servers.
        
        Types of Server
        
        Characteristics of Client/Server System
    - - Simplex System This system consists of one CPU only. Reliability and the processing capabilities are inferior in comparison with other configurations, but it is economical.
      - Dual System This is a system configuration in which two CPUs perform the same processing and compare the processing results to each other.
      - Duplex System (Standby System) In this system, two CPUs are prepared, where the primary system is used for online processing while the secondary system is used for low-priority processing such as batch processing.
      - Multiprocessor System (Concurrent Processors) In this system, multiple CPUs and CCUs are sharing and processing tasks, so it is a system configuration with high processing efficiency.
    - - Centralized ProcessingCentralized Processing Centralized processing is a system configuration in which one computer is connected with many terminals, and the one computer alone does all of the processing.
      - Distributed Processing Distributed processing is a system configuration in which multiple computers connected via anetwork perform the processing. Since the processing is done through a network, the processing time is longer than that of centralized processing.
    - - Batch Processing Systems (One-Time Processing
        Systems) Batch processing is any method in which data to be processed by a computer are stored for a certain period of time or are saved on original sheets or storage media and are later processed all at once.
      - Interactive Processing Systems This is a method in which the processing is performed in the mode of a dialogue with the computer.
      - Online Transaction Processing Systems A transaction is a series of data or instructions, sometimes called a transaction file or transaction data. Online transaction processing refers to the processing of data updates on an online file at the computer center via a connected online terminal.
      - Real-Time Control In general, real-time control refers to the method by which data is processed in real time once a processing request is made and the result is immediately reported to the requester.
  - - - Terms Related to Performance Evaluation of Computer
        Systems In evaluating the performance of computer systems, it is important to calculate the processing time of jobs and programs.
        
        Response time
        
        Throughput (Processing capability)
        
        Turn-around time (TAT)
      - Instruction Mix An instruction mix is used to compare the performance of hardware in computer systems.
      - Benchmark A benchmark is used to compare and evaluate the comprehensive performance of computers, including the hardware and the OS, by measuring the standard program execution time.
    - - Reliability Indexes Reliability is the degree to which system operation is stable. The ideal case is that the system does not fail, but there is no system that does not ever fail.
        
        RAS/RASIS Both of the terms RAS and RASIS are acronyms of elements that help computer systems to
        operate in a stable manner. RAS stands for the first three elements of RASIS:
        
        Bathtub curve The bathtub curve is used to illustrate the concept of hardware lifecycle.
      - Reliability Design Points A highly reliable system that can continue to operate even when some part of the system fails is called a fault-tolerant system
        
        Fail-soft This refers to the function in which, when a failure occurs, the failed part gets cut off and the system continues to operate, perhaps with a lower performance level (fall back114)
        
        Fail-safe This refers to the function in which, when a failure occurs, the system locks its functions in a safe mode established in advance to control the extent of the impact of the failure.
        
        Fool-proof This term refers to a measure that prevents an unintentional use of a program from causing a failure, especially when indefinitely many users use the same program.
    - - MTBF and MTTR
        
        MTBF (Mean Time Between Failures) MTBF = (T1 + T2 + T3 + … Tn) / n “n” is the number of intervals the system was operating without failure
        
        MTTR (Mean Time To Repair) MTTR = (D1 + D2 + D3 + … Dn) / n “n” is the number of intervals the system was operating without failure.
      - Calculation of Availability To calculate the availability, the serial connection and parallel connection sections must be calculated differently. The basic ideas are described below.
        
        Availability in a serial connection system
        
        Availability in a parallel connection system
        
        Availability in a system where serial and parallel connections are combined
  - - - Uses of Infrastructure “Infrastructure” means “foundation” or “basis.” In computer systems, this word refers to the foundation of software and hardware to form the systems.
        
        Web (WWW: World Wide Web) This is the information search system in the hypertext format, developed by researchers at CERN.
        
        Intranets An intranet is a company-wide network applying the technology of the Internet Normally, a firewall123 is set up between the Internet and a company-wide network in order to prevent leakage of confidential information of the company.
        
        Extranets An extranet is an intranet extended over numerous companies. In general, an extranet is built by connecting intranets to the Internet.
        
        Mobile communication is an environment in which the network can be accessed from any
        location.
        
        Satellite communication is a wireless communications system using a communications satellite.
        
        CATV New types of services using CATV (Community Antenna TeleVision, or Cable TV) are being considered and discussed commercially, such as Internet connection, telephone services, experiments involving PHS (Personal Handy-phone System), and VOD (Video On Demand). CATV is expected to be a major part of the infrastructure in the multimedia era.
      - Application Systems
        
        Internet shopping This is a system in which the user can shop at a virtual store set up on web pages. To make a
        payment, the shopper can use his or her credit card or go to a nearby convenience store to pay
        
        Groupware This is software for communication within an organization or for information sharing. It has
        functions such as electronic mail, schedule sharing, document sharing, and workflow
        
        Debit cards This is a service whereby a cash card issued by a bank can be used to make payments. The money
        for the payment is directly withdrawn from the bank account in real time
    - - Data Warehouse A data warehouse is a company-wide database to support decision-making
      - Data Mining This refers to a technology or method of drawing out tendencies, trends, correlations, and patterns necessary for management and marketing, through dialogues with a large amount of raw data.
      - Data Mart A data mart is a database which stores data obtained from a data warehouse. The data stored in
        a data mart, is selected and summarized according to the purposes of a specific user group
      - OLAP (OnLine Analytical Processing) is the concept of analytical application in which the end user discovers problems and solutions by directly searching and organizing a database
      - OLTP OLTP (OnLine Transaction Process) is the processing mode in which messages are sent to the host computer from multiple terminals connected online to the host computer, which, according to the message received, in turn performs the process including access to a series of databases and returns the process results immediately to the terminals
      - Application Systems
        
        Data can be easily accumulated.
        
        Data can be managed in an integrated manner.
        
        Data can be easily processed.
        
        Data can be easily searched.
    - - Artificial Intelligence (AI) Artificial intelligence refers to a system that performs inference processes such as an expert system 133 and a machine translation system. Lisp and
        Prolog are languages suitable for developing software using AI technologies
      - 3-Dimensional Graphics (3D Computer Graphics, or
        3DCG)
      - Multimedia Application Systems
        
        Internet broadcasting This is broadcasting using multimedia on the Internet. With the use of streaming distribution technology, 136 programs are broadcasted in real-time on the Internet
        
        Non-linear editing This is a method of video editing where images are digitized and video is produced in free order using a computer.
        
        Video on demand This refers to the service of instantly sending a video program requested by the viewer via, for example, bidirectional CATV The service provider stores many video programs on its video server and distributes the one requested by the viewer
- - - - Classification of Programming Languages
      - Programming Languages
        
        Markup languages (document-formatting languages)
        
        Other programming languages
        
        Script Languages A script language is a language that uses text (characters) to describe procedures to be executed by the computer. The processing procedures described by a script language are called scripts.
    - - Program Structures
        
        Recursive A procedure is said to be recursive if the definition of that procedure refers to the procedure itself
        
        Reusable This term refers to the program structure that allows multiple programs (tasks) to share the use of the program without reloading the program into main memory each time.
      - Subroutines (Subprograms) A subroutine refers to a part of a program which is repeatedly used within the program to execute common procedures.
        
        Open subroutine An open subroutine11 is a subroutine that is embedded wherever a program needs it as many times as the program needs it.
        
        Closed subroutine A closed subroutine is created independently of programs that need it as a subroutine. If a program needs the subroutine, it executes a subroutine-call instruction (usually a CALL statement) to deliver the control to the subroutine.
    - - Language Processors
        
        Assembler Translates assembler language to machine language
        
        Compiler Translates compiler language14 to machine language. (COBOL, Fortran, C, etc.)
        
        Generator Creates programs by giving parameters. (RPG, etc.)
        
        Interpreter Executes while translating instructions. (BASIC, APL, LOGO, etc.)
      - Procedures of Compiler A compiler language is translated to machine language in the order below. A program translated into machine language is called an object program (also an object module).
      - Creation of Load Modules Computers can read and execute only machine language, so any program written in a language other than machine language must somehow be translated into machine language. One way to do this is to use a compiler.
      - Execution of Program To execute a program, it is necessary to store the program to be executed in the main memory or in a virtual memory. This function is performed by a loader. A loader stores a load module in the main memory, and then the computer takes out one instruction at a time from the load module, interprets it, and executes it.
    - - CASE (Computer Aided Software Engineering) Tools CASE is a group of software that supports system development and automation of maintenance work. CASE contains shared databases which store information necessary for development, such as requirements and design information for system development.
      - Test Support Tools Test support tools analyze a program and monitor the operation of the program during execution.
      - EUC (End User Computing) refers to the idea that the end user himself or herself performs processes such as design, development, operation, and maintenance of information systems. System integration and development by end users are called EUD (End User Development), but in practice the difference between EUC and EUD is not clearly identified.
      - Software Packages is “general-purpose software that general users can commonly use.”
        
        ERP (Enterprise Resource Planning) is the concept of planning optimization of management resources through company-wide understanding of business information.
        
        CRM (Customer Relationship Management) is the concept that all departments which have contact opportunities with customers should share and manage customer information and contact history so that any questions from the customers can be answered appropriately.
        
        SFA (Sales Force Automation) is the basic concept of information systems that facilitate workrestructuring of the entire sales activities that support corporate profits by using information technology.
        
        CTI (Computer Telephony Integration) is technology that provides a high level of telephone services by combining the information processing functions of computers and the communication functions of telephone switches.
    - - Process Models is a model abstracting the process of system development.
      - Cost Models is a model to quantify the cost (i.e., productivity) such as the productivity and quality measures of the software.
    - - DFD (Data Flow Diagram) DFD is a diagram showing the flow of data (data flow). Flow of materials (objects) and money is not included. DFD is data-oriented approach. In DFD, the system is expressed using the symbols shown in the table below.
      - E-R Diagram (Entity-Relationship Diagram) E-R diagram is a figure that shows relationships between entities. An entity can be aperson, an object, an event, or a concept which needs to be managed in business processes, and each entity has attributes.
      - Object Orientation means to model the data and their operation (process) together. Integrating
        data and operation is called encapsulation.
    - - Review Methods is a discussion meeting held at the end of each process in order to avoid carrying the existing problems over to the next process in system development.
      - Growth Curve In the testing phase, the relationship between the accumulated number of detected errors and time (period) is said to be similar to the growth curve.
      - Error-Planting Model is also called the error-spreading model or the bug-embedding model. In this model, errors are intentionally placed in the program.
      - Software Quality Characteristics are the standards by which the quality of the software is evaluated. ISO/IEC9126-1, which includes international standards of quality characteristics of software, includes the six characteristics listed in the following table.
  - - - Procedure of External Design External design is the activities of collecting and analyzing the system requirements given by the user and establishing the system functions based on the results.
      - Points to Remember in Screen Design In screen design, it is important to design with the idea of making the interface compatible with the user (human interface).
        
        Consider the source of data, amount of data, number of items and digits, attributes, etc. Place input items so that they can flow from top to bottom and left to right. Try to standardize the screen layout and operability. Keep message representations consistent. Consider the possibilities of aborting an operation midway or re-starting from the previous
        screen.
      - Points to Remember in Output Design refers to designing the output format of the system, including screen display and printing.
        
        Set up sequence and positions in consideration of the relationship among the items.Ensure that the title appropriately expresses the printed contents.learly distinguish various dates such as the date prepared, date reported, and date approved.Position the items with appropriate spacing. Plan for the entire report to have sufficient empty space.Consider the design so that critical items can be immediately identified.
      - Code Design Codes need to have the functions listed in the table below. When designing, we must consider various properties such as commonality, systematization, expandability, and clarity
        
        Identification A function to distinguish data.
        Codes can distinguish between two people with the same first and family names.Classification A grouping function; classifying by affiliation code, etc.Listing A sorting function: If the digits are aligned, data can be sorted by date of birth.Checking A function to check input values; for instance, by adding a check digit.
    - - Procedure of Internal Design
        
        File Design The organization and medium of files need to be decided according to the purpose of their use. For backup, various media are used, including magneto optical disks (MO), floppy disks (FD), CD-R, CD-RW, DVD-R, DVD-RAM, DAT, etc.
      - Check Methods
      - Check Digit Method This is the method which determines whether an input error is made when a code is entered byperforming the same calculation when the code was created and by comparing the calculation result with the code.
    - - Structured Design Techniques The structured design is the technique of designing based on the approach of structuring.
        
        Bubble charts These charts use bubbles (circles) to represent processes that convert input data into output data and are the same as DFDs. For every system, there is only one initial bubble, but as break-down (structuring) continues, bubbles and data flow become more complex
        
        Design Techniques based on Data Structure
    - - Structural Evaluation
        
        Size: Are they too small or too big? (Criteria should be set.) The proper size differs
        depending on the language used (about 300 steps for COBOL).Function: Are there unnecessary functions? Are there multiple functions? (If there are
        multiple functions, partition them again.) Interface: Are there too many parameters? (In such a case, review the partitioning.)
      - Evaluation of Independence To evaluate the independence of modules, there are two measures—module strength and module coupling. Partitioning is considered good if its modules have a high level of independence.
    - - Structure Theorem “In a valid program, in which there is a pair of an entrance and an exit, no infinite loop, and no statement that is not executed, we can write the logic only using three basic control structures: sequence, selection (decision), and repetition (iteration).”
      - Basic Control Structures
      - Graphic Expressions of Module Design
    - - Order of Tests
        
        Unit test A unit test is a quality test for modules (smallest units within a program). In a test of the entire program it can be difficult to identify the cause of an error, so unit tests are performed for each module as a unit. In unit tests, we perform function tests52 and structure tests.53 Since modules do
        not function by themselves, we prepare drivers and stubs
        
        Integration test Methods for integration tests include top-down tests, bottom-up tests, big-bang tests, and sandwich tests
        
        System test This is the last test conducted in the development division and is used to examine whether the required specifications are satisfied.
      - Order of Integrated Tests
    - - Black Box TestsA black box test is the method whereby test cases are designed based on the external specifications of the program. Regardless of the program logic, test data is prepared based on the external specifications.
      - White Box Tests A white box test is the method whereby test cases are designed based on the internal specifications of the program. Below are some of the test criteria: instruction coverage, decision condition coverage (branch coverage), condition coverage (branch condition coverage), decision /condition coverage, and multiple condition coverage.
- - - - OSI Basic Reference Model. The OSI (Open Systems Interconnection) basic reference model is a model of complex protocols, in which a network is partitioned into seven independent layers from a functional standpoint.
        
        Layer 4 Transport Absorbing the difference between communication networks and achieving a
        communication function that is highly reliable and economical
        
        Layer 3 Session Deciding the control methods such as connection and disconnection of lines for proper
        conversation between users, including the starting and ending of the communication
        
        Layer 5 Network Selecting relays and routes in communication networks to provide network service
        between terminals
        
        Layer 2 Presentation Deciding character set, data format, and data expression format for encryption and
        compression
        
        Layer 6 Data link Stipulating the detection of transmission errors, way of synchronizing, and control of
        re-sending data so that data can be correctly transmitted
        
        Layer 1 Application Deciding data format and contents between users
        
        Layer 7 Physical layer Stipulating the connector shape/type so that terminals can be connected to a communication line, as well as electrical conditions and physical properties for bit transmission
      - TCP/IP (Transmission Control Protocol/ Internet
        Protocol) TCP/IP is the protocol widely used on the Internet and other networks. UNIX workstations are equipped with this protocol as a standard feature. Programs used on the Internet, such as FTP, use services provided by TCP/IP.
      - IP AddressesAn IP address is a 32-bit network address used on the Internet and can be classified into several classes according to the network size. Each class is identified by the leading bit pattern of 1 to 3bits.
    - - Basic Procedure (Basic mode data transmission control procedure) is a procedure of control using 10 transmission control characters. The text is the transmitted data, consisting of a set of 8-bit character codes. Each transmission control character is also 8 bits long.
        
        Contention method
        
        Polling/selecting method
      - HDLC Protocol (High-level Data Link Control) is a transmission control procedure aiming to achieve highly efficient and reliable data transmission between computers. Transmission is performed by blocks of data called frames.
        
        HDLC has the following characteristics: Bit-oriented (possible to transmit an arbitrary bit pattern) Continuous transfer (possible to transmit without getting a response within the limits of the
        certain number of frames) Strict error check (using CRC) Full duplex communication (cf. Sec. 4.2.3) is possible even in multi-drop lines.
  - - - Parity Check Method is the error detection method in which the number of 1's is set to be even or odd by adding one bit, horizontally or vertically, to characters transmitted in binary code. Making the number of 1's even is called even parity check while making it odd is called odd parity check.
      - CRC (Cyclic Redundancy Check) is a method of using the remainder resulting from division by a certain polynomial as the check bit. For each transmission unit, the bit string is considered a binary number.
    - - Bit Synchronization (Asynchronous) is a synchronization method which designates a start bit indicating the beginning of data (one character) and a stop bit indicating the end of the data.
      - Character Synchronization (Synchronous) is the method in which an SYN code (10010110)2 is placed before a data block as a synchronization code.20 The SYN code is sent consecutively multiple times just to be sure. At the receiving end, when the SYN code is received, the following bits are divided into 8-bit units, each of which is recognized as a character
      - Block Synchronization (Synchronous) a special bit string for synchronization is sent attached to the front and the end of a series of transmitted blocks.This bit string is called a flag sequence, indicating the
        first and the last positions of the transmission block
    - - Multiplexing Methods
        
        FDM (Frequency Division Multiplexing) is the method of multiplexing with a frequency division multiplexer23 to divide the transmission frequency bandwidth of an analog line into multiple small bands and to use each channel as an independent communication channel.
        
        TDM (Time Division Multiplexing) is the scheme of dividing one digital line into multiple low-speed channels. For instance, if a line whose speed is 64 Kbps is connected to 16 terminals, then each terminal has a speed of up to 4 Kbps.
        
        WDM (Wavelength Division Multiplexing) eliminates this disadvantage; it is the method of transmitting multiple optical signals with different
        wavelengths on one optical fiber.
        
        Transmission Methods Transmission can be classified into three methods by the way data flow; they are simplex,
        half-duplex, and full-duplex.
    - - Circuit Switching Under circuit switching, the transmitter calls up the other party by dialing to set up a physical circuit, as represented by the telephone service. This enables high-speed and high-quality data transfer, but both parties are required to use the same speed and same transmission control system.
      - Store-and-Forward Switching Under store-and-forward switching, the transmitted data is first stored in a switching unit, the receiver is selected, and then the stored data is transferred to the next switching unit or to DTE.
  - - - Topology of LAN The word “topology” here refers to a connection configuration of a network. Typical topologies of
        LAN include the star, ring, and bus networks.
      - Access Control of LAN Access control methods of LAN can be classified into the following. The bus and ring networkshave only one transmission channel, so it is necessary to control communication to prevent collision between the transmitted signals. CSMA/CD (Carrier Sense Multiple Access with Collision Detection), Token passing
      - Specifications and Transmission Media for LAN
      - Wireless LANuses transmission channels other than cables, such as radio waves and infrared rays.
        Most of the cables can be eliminated, so it hardly takes any labor to install or move terminals
    - - WWW (World Wide Web) is the concept of creating a gigantic information space by mutually connecting information spread apart on the Internet like a spider “web.”
      - Internet Services The Internet uses TCP/IP, so most of the services that can be used with TCP/IP are available on the
        Internet.
      - Intranets is an in-house (company-wide) network using Internet technologies. Normally, between an in-house network and the Internet, a defense system called a firewall is installed to prevent critical in-house information from leakage.
      - Extranets An extranet is a network in which intranets are extended between companies. In general, intranets
        are connected to the Internet to construct an extranet.
      - HTTP (HyperText Transfer Protocol) is the communication protocol for sending and receiving HTML documents between a WWW server and a WWW client on the Internet.
    - - Connection Units between LANs is a device mutually connecting multiple LANs or networks of
        different protocols. The following figure shows the correspondence between each unit and the OSI
        basic reference model
      - Communication Units for Analog Lines is used in a data communication system that utilizes the
        public telephone network (analog) as its transmission route.
      - Communication Units for Digital Lines is a transmission system using a digital line as its
        transmission route.
    - - ISDN (Integrated Services Digital Network) is a communications network integrating a variety of services including telephone, data, and
        fax services. It provides the basic rate interface and the primary rate interface.
      - ATM (Asynchronous Transfer Mode) partitions all information into cells of fixed length (53 bytes) for transmission and reception. With the assumption that a high-quality line is used, this mode has achieved high speeds by simplifying protocols such as error control and performing the partitioning process on the
        hardware.
      - ADSL (Asymmetric Digital Subscriber Line) is the technology for high-speed data transfer using
        existing telephone lines. This can be used simply by connecting an ADSL modem to the
        conventional equipment. The speeds are 0.5M to 1Mbps upstream and 1.5M to 40Mbps
        downstream.
- - - - Independence of Data means that the “program does not get changed when data changes.” Since multiple programs share the same set of data, it is not necessary to create as many data
        sets as the number of individual programs
      - 3-layer Schema
    - - Hierarchical Database (Tree-Structure Database) divides records into parents and children and shows the relationship
        with a hierarchical structure.
      - Network Database is different from a hierarchical database in that the parent records and child records do not have 1-to-n (1:n) correspondences; rather, they are in many-to-many (m:n)
        correspondence
      - Relational Database is a database in which data is expressed in a two-dimensional table. Each row of the table corresponds to a record, and each column is an item of the records.
      - Bachman Diagramdescribes the parent-child relation between records in a network database. A parent is called an owner while a child is called a member.
    - - Rules for E-R Diagram In an E-R diagram, entities are represented in rectangular boxes while relationships are indicated by line segments or arrows (Å, —, Æ).
      - Correspondence Relations In an E-R diagram, the 1-to-many relation “one company has multiple employees” is indicated by the following diagram. Note that, as seen here, sometimes the attributes are omitted.
    - - Non-normal Form is a form in which items are simply listed. In general, repeated items are also included.
      - First Normal Form has no repeated items in the table. To convert a non-normal form into a first normal form, we separate the combination “ProductNumber, Quantity, UnitPrice” in the non-normal form.
      - Second Normal Form
      - Third Normal Form
      - Reference constraint is a constraint concerning the consistency between multiple items. If a table contains data that looks up another table, the other table must have the referenced data registered in advance.
    - - Relational Operations The meanings of relational operations are listed in the following table. Various data is extracted
        by combining these basic operations.
      - Set Operations A set operation, based on the mathematical theory of sets, includes the following:
  - - - DDL (Data Definition Language) is a language system that defines schema based on the data model. For relational databases,
        they are stipulated as SQL-DDL
      - DML (Data Manipulation Language) is a language system used to manipulate databases by the user. For relational databases, they are stipulated as SQL-DML. According to how they are used, DMLs are classified as shown
        below
      - Cursor Functionis used when processing rows (records) of a relational database by using a procedural language.
    - - Structure of SELECT Statement
      - Projection and Selection
      - Join
      - IN and BETWEENSELECT Name FROM Employee_tbl WHERE Age IN (22, 28, 35) , SELECT Name FROM Employee_tbl WHERE Age BETWEEN (22, 28)
      - ORDERED BY SELECT Name FROM Employee_tbl ORDERED BY Name ASC , SELECT Name FROM Employee_tbl ORDERED BY Name DESC
      - Set Functions and GROUP BY
      - Subqueries SELECT ProductModel FROM Product_tbl WHERE Product_tbl.ProductNumber IN (SELECT Order_detail_tbl.ProductNumber FROM Order_tbl, Order_detail_tbl WHERE CustomerNumber = 'A100' AND Order_tbl.OrderNumber = Order_detail_tbl.OrderNumber)
  - - - Two-Phase Commitment is a mechanism that ensures the integrity of a distributed database and is
        important in ensuring the integrity when the database is updated
      - Replication is the mechanism of automatically reflecting updated contents in a copy (replica) of the database on the network
    - - Access Control Exclusive access control prohibits multiple users from accessing the same data at the same time. A deadlock is a situation in
        which two transactions are waiting for each other to release the lock
      - Shared Resources Management Multiple users access a database through applications; here, data editing and updating need to be completed by only one application.
      - Recovery Management
- - - - Encryption means to scramble information by a certain pattern so that a third party cannot understand its contents Depending on the combination of keys for encryption and for decryption, there are private key cryptography (common key cryptography) and public key cryptography
      - Authentication means verifying that the user is, without a doubt, a valid user. There are various authentication methods as listed in the table below.
      - Access Management means preventing unauthorized access to recourses (such as data) in a
        computer system.
    - - Computer Viruses or, simply, a virus, is a malicious program that enters a system via networks or storage media, and destroys, falsifies, or steals data.
      - Vaccines (Vaccine Software, Computer Vaccines) is a program that discovers and eliminates computer viruses.
      - Anti-Virus Measures In order to prevent computers from being infected by computer virus, the following points need
        to be observed
      - Firewalls is a system (mechanism) that protects an internal network such as an in-house LAN from unauthorized access from the outside.
    - - Falsification refers to the act of intentionally changing data or programs in a computer and includes falsifying or modifying a document, replacing storage media with a false version prepared in advance, rewriting data, and erasing data.
      - Destruction is the act of erasing critical data or a program stored in a computer or disabling
        system devices or storage media by physically destroying them.
      - Leak is a collective term referring to the robbery of data or copies from an information
        system.
      - Tapping is the act of illegally intercepting data on a network and stealing information or
        illegally accessing a computer system.
      - Disguise is the act of stealing someone else's user ID and password and acting on a network
        using the stolen identity.
  - - - Standardization Organizations
        
        ISO International Organization for Standardization
        
        ITU International Telecommunications Union
        
        ANSI American National Standards Institute
      - ISO 9000 Series is a collective title given to the multiple international standards established by
        ISO concerning the quality-assuring structure of corporations
        
        ISO 9001 Quality management systems — Requirements Management responsibility (customer focus, quality policy, review, etc.) Resource management (provision of resources, human resources, work
        environment, etc.)Product realization (planning of product realization, customer-related
        processes, design and development, etc.)Measurement, analysis, and improvement (monitoring and measurement,
        control of nonconforming products, etc.)
        
        ISO 9004 Guidelines for performance improvements
      - ISO 14000 Series is a group of international standards set by ISO concerning environmental
        protection management.
    - - Character Codesis a code assigned to each character and symbol for the purpose of processing
        those characters and symbols on computers.
        
        EBCDIC Extended Binary Coded Decimal Interchange Code Character code established by IBM for general-purpose computers.
        A set of 8 bits represents one character.
        
        Unicode(UCS-2) Standard for expressing the characters used all over the world in one integrated character code All characters are expressed using 2 bytes.
        This is adopted as part of international standards by the ISO.
      - Image Files is a file in which a still image like a photograph or an illustration is digitized as a
        file.
        
        JPEG(Joint Photographic Experts Group) ,GIF(Graphic Interchange Format) , BMP , TIFF(Target Image File Format)
      - Moving Picture Compression MPEG is the
        name of a lower organization of JTC1, which is a joint organization of ISO and IEC. It is a method for compression/decompression of moving pictures, which was established by this group.
      - Document File Formats are standardized so that document data and data prepared using an application can
        be exchanged easily.
    - - Standardization of Data Exchange
        
        EDI Electronic Data Interchange (electronic transaction, electronic data exchange)
        
        CALS Commerce At Light Speed
        
        EC Electronic Commerce
        
        STEP Standard for the Exchange of Product Model Data
      - Open Systems is a computer system constructed in such a way that, by standardizing the specifications, hardware and software can function without conflict, regardless of the manufacturer.
      - Standardization of Software
        
        CORBA Common Object Request Broker Architecture
        
        EJB Enterprise JavaBeans
        
        RFC Request for Comments
        
        OMG Object Management Group
- - - - CIO (Chief Information Officer) is the highest-ranking officer in charge of overseeing
        information systems.
      - The KJ method is named after the initials of Jiro Kawakida, the inventor of the method. In this method, various ideas are generated to solve one problem, and these ideas are grouped together and related with one another.
      - Brainstorming is a type of meeting which is held under the guideline that absolutely no
        criticism is allowed on remarks made by the participants.
      - OJT (On the Job Training) is training in an actual work setting.
      - Off-JT (Off the Job Training) training is targeted for certain employees and is
        conducted outside the usual workplace separate from their daily work.
    - - DSS (Decision Support System) is a system that supports decision-making by managers and
        administrators facing non-structured problems (non-routine task)
      - SIS (Strategic Information System) is an information system that actively uses information
        technology as a part of its corporate strategy to obtain a competitive edge.
      - Work Improvement, Analysis, Design
        
        BPR (Business Processing Reengineering) is the work of modifying the actual business contents and/or organization, restructuring the business field, based on an analysis of the business contents and business flow, and redesigning for optimization in order to achieve the target level profit or
        customer satisfaction.
        
        A business model is a framework for making business concepts concrete. In other words, it is a
        template for how to carry out business to generate profits.
      - Business Using the Internet
        
        e-business is a new business structure which takes advantage of the Internet and computers.
        
        Dot com business (.com business) is a collective term referring to general business activities
        using the Internet.
        
        SOHO (Small Office Home Office) is a term coined by joining the phrases small office and home
        office.
  - - - B/S and P/L A balance sheet (B/S) is a document that shows the financial status of the company at a particular
        point in time, indicating the relationship between assets, liabilities, and capital. (P/L) is a document that shows the business results for one accounting fiscal year,
        indicating the relationship between expenses and revenues (sales).
      - Configuration of Account List An element that forms asset, liability, or capital on B/S and P/L is called an account item
      - Depreciation is a method of reducing the value of a fixed asset by assigning the cost for acquiring
        the fixed asset13 as an expense according to a certain method. As shown below, there are several
        methods including straight-line and declining-balance methods.
    - - Break-Even Point Analysis is a point where the revenue (sales) becomes equal to the total cost (variable
        cost + fixed cost)16, i.e., the point where the profit becomes 0.
      - Financial Analysis is conducted to evaluate the management records and financial conditions by
        analyzing the safety and profitability of a company. For indexes in financial analysis, relation
        ratios are often used.
        
        Ratios of safety are ratios whereby the debt-paying ability of the company is evaluated.
        
        Ratios of profitability are indexes showing how much profit the company is making.
        
        Costs are the expenses required to manufacture and sell products
        
        Inventory Evaluation Inventories are defined as assets that will be converted to cash by sales or be consumed for
        manufacturing the products.
  - - - Seven QC Tools are tools used to analyze mainly quantitative numerical data as shown in the
        following table
      - ABC Analysis Goods in an inventory can be grouped by item of goods, and then each group can be arranged in descending order by inventory price (inventory configuration ratio) or by sales revenue (sales revenue configuration ratio).
      - New Seven QC Tools are mainly used in quantitative and numerical data analysis, the new seven QC tools provide a method to handle qualitative data such as language data.
    - - Arrow Diagrams is suitable for managing large-scale projects in which multiple activities run
        parallel. An example of an arrow diagram is shown below.
      - Solution by Arrow Diagrams
        
        Forward calculation
        
        Backward calculation
        
        Critical Paths A path connecting nodes where the latest node time and the earliest node time are identical is called a critical path. In the arrow diagram shown above, a critical path is “A→C→ dummy activity→ I” (○1 →○2 →○4 →○7 →○8 ).
        
        Concept of Schedule Reduction
        
        Dummy Activities is an activity without substance and is expressed by a dotted line. This is used only to indicate the time relation between two activities.
    - - Constraint Conditions/ Objective Function
      - Solving Method
    - - Purpose of Inventory Control
      - Ordering Systems
      - EOQ (Economic Order Quantity) Formula
        
        M Firm demand for a fixed period (e.g., a year)
        
        K Ordering expense per order
        
        P Purchasing unit price
        
        c Inventory maintaining rate
        
        x Quantity ordered per order
        
        n Number of orders for a fixed period (e.g., a year)
    - - ProbabilityWhen a die is rolled, one of the outcomes 1 through 6 will result. The numbers 1 through 6 here
        are called a random variable. The probability of each of these outcomes is 1/6, totaling 1
      - Mean/ Variance/ Standard Deviation If a sample is drawn from a population, various tendencies of the population can be estimated by calculating the sample mean, sample variance, and sample standard deviation.
      - Binomial Distribution is the discrete probability distribution in which P(x) represents the
        probability that an event with probability P occurs exactly x times in n trials.
      - Normal Distribution is a continuous probability distribution, and it approximates binomial distribution when the probability P is not small and n is large
      - Correlation Coefficient Two quantities are said to have a correlation if there is a tendency that when one increases, so does
        the other, or when one increases, the other decreases.
  - - - CAD (Computer Aided Design) refers to the use of an interactive format to carry out detailed design work, including the
        minute shapes and dimensions of each part of a product as well as the materials.
      - CAM (Computer Aided Manufacturing) is manufacturing work using computers, applied over a wide range of applications, from
        small-scale manufacturing activities to large-scale processes using robots.
      - FA (Factory Automation) is a system that organically integrates and manages the entire production system including production planning, ordering, fabrication, assembling, testing, inspecting, transporting, storing, and delivering. Conceptually, FA contains all of CAD, CAM, and CAE, including CAT,53
        assembly, fabrication, and process control
      - CIM (Computer Integrated Manufacturing) is support and management using computers to integrate research and development, design,
        manufacturing, sales, and management control.
    - - POS (Point of Sales) system is a real-time data-processing system where sales data such as product codes and prices are entered at the point of sales using a terminal unit called a POS terminal located in
        supermarkets and retail stores.
      - EOS (Electronic Ordering System) manages the inventory properly to ensure that the store is sufficiently stocked and excessive
        inventory is reduced.
      - Electronic Banking is a system in which computers of financial institutions and computers or terminals of individuals and corporations are connected by communications lines whereby data such as fund transfer and balance inquiries is transferred electronically.
      - Card Systems including those listed in the table below are provided to maintain the customer base
        or to bring in new customers. Payment methods and the need for an ID depend on the card. Bank
        POS is used as debit cards
      - Groupware is a family of software used to efficiently communicate andr share information within
        an organization such as a company.
      - PC Communication means connecting PCs by a communications line to a host computer providing a PC communications network so that PCs can communicate with one another and receive various services, including electronic mail, electronic bulletin boards, electronic conference rooms, and information services.
      - Commercial Databases is a database that provides, for a fee, business information such as information on a company, science/technology-related information, and patent information. Generally, this service uses databases via a communication line such as a PC communication
        service