Software is the key of virtual instrument, design a virtual instrument system, the hardware platform was determined, can design different software, achieve the function of different instruments,
In the design and implementation of virtual instrument software system, the need to consider many factors, such as hardware requirements, computer hardware, operating systems; The structure of the software is built on open, need programming experience? Can use this software program on different computer platforms transplant? Whether convenient extended the function of virtual instrument in the future, due to choose special software development, must have certain instruments and data collection devices,
Application of modular design overview
Data acquisition system performance depends largely on its research and development of application software and so on has been clear about the system design goal, should adopt good application development methods, such as structural design method of modularization thought, multithreading and evaluation standard of the software system, etc.,
Principles of modular program design
Modular structure is well designed all the basic characteristics of the software system, the application system of any one big, always is composed of several function relatively independent modules, good software structure should reflect the top-down control mode, the module control show the commander in chief and the subordinate relationship between [13],

Figure 4.1 modular structure
Implied information abstraction and information is the basic characteristics of the Module, the Module (Module) actually reflect the Data (Data) and the Process (Process) of the abstract, the modular problem solving, at the highest abstraction level can be used in a problem oriented language environment of abstract term is described; While at lower abstract level, and can use procedural terminology, the concept of modularity and stepwise refinement method, the problem oriented terms and implementation oriented terms both combined,
Module independence has two qualitative standard metric: namely block contact between (cohesion) and block (coupling), as shown in figure 4.1, the connection between blocks is refers to the connection between the modules, connection between block is smaller, the higher module independence, block contact refers to the module internal parts (statements and statements), the relation between a module block contact, module independence will improve, module structure, connection between block should be as small as possible, contact should be as large as possible inside the block,
The modular design principle of software system
In order to develop the software has a good reliability, easy maintenance, easy to expand and easy handling, the software design should follow the principle of standardized modular design [13],
1) the top-down design method of incremental refinement
Software design are often don't understand the problem at the beginning of all the details, can only make global decisions, the problem of design representation to solve the problem that the general strategy of the abstract algorithm, the abstraction algorithm for further refinement, into the next layer of abstraction, every step of the process of refinement, abstract concept (statements or data) are fine,
2) according to the logical functional division physical module
Module decomposition: eliminating repetitive function part, make the module block high level contact, contact between blocks is low,
(2) merge module;
(3) module of copying,
3) module scope should be in module control
Module scope refers to the module and the scope of influence, as long as rely on a certain decision operation is contained in a module, this module is in the range of the role of the judge,
4) according to the logic functions determine the invocation of the relationship between modules
Module between the call and is called, is determined by their respective logical function module, and the module of the fan in the fan out is not necessary to limit, in general, the module of the fan in high, fan out is higher, the top-level module
5) module interface should be kept concise
To reduce the complexity of the module interface, is must consider the question of module design, keep the module interface simple, on the one hand, must reduce the amount of information transmission between modules, more important is the necessary information to the passed with a clear logical meaning,
6) module should maintain a single entrance properties
Single entry module, easy to understand, due to the less side effect, can reduce the incidence of errors, there can be multiple module exports, but all should have clear logical meaning,
7) module structure judge between layers are added to improve scalability
Figure 4.2 a, module a call B, later extended to make a call C (figure 4.2 B), when such extension, in addition to the increase in C, has yet to modify a, this change may be difficult,
Figure 4.2 c, added A judge between F layer module, with A switch quantity Flag decided to call A module, for A change, so only limited to Flag set, greatly reduce the workload,

Figure 4.2 module structure increase judgment level
The design of the software system module partition
The main functions of the system program for module partition standard, other including system management, data acquisition, data storage, historical data query functions, such as concrete structure as shown in figure 4.3 the multichannel data acquisition function module diagram,

Figure 4.3 the multichannel data acquisition function module chart
Database technology
Database technology mainly studies how to store, use and management of data, is a new stage of development, the computer data management technology and computer technology, the fastest growing in one of the most widely used technology, at present, the database technology has become the core of the modern computer information system and application system development technology, database has become a computer information system and application system of the core, in some ways, the construction of the database size, the size of the database information and using the frequency has become to measure a national informatization level of important symbol,
Database technology overview
Database technology involves the following a few of the most important concepts:
1) DataBase (DataBase) is stored in the computer for a long time, organized, and Shared collections of data, data in the DataBase according to certain data model organization, description and storage, with smaller redundancy, high data independence and extensibility, and can provide a certain range of all kinds of users to share, the DataBase should not only reflect the content of the data itself, but also reflect the connection between the data, using the data in the DataBase model (DataModel) is a tool to abstract, representation and processing of the data and information of the real world,
2) data model is the characteristic data abstraction, describes the common data, the data model should meet the requirements of three aspects: first, can more truly simulate the real world; 2 it is easy to understand; 3 it is easy to realize on a computer, a data model to well meet the requirements of the three aspects in it is very difficult, in a database system for the use of different objects, and application purpose, adopt the method of gradual abstraction, at different levels have different data models, generally can be divided into three layers, namely the physical layer, logic layer and layer concept,
The physical layer is the lowest level of data abstraction, which is used to describe the physical storage structure and data storage method,
Logic layer is data abstraction layer, describe the logical structure of the database data as a whole,
Concept layer is the highest level of abstraction, the aim is to Model according to the user's point of view to the world, such as Entity - relationship Model (Entity - Relational Model, ER Model for short),
3) DataBase Management System (DBMS, the DataBase Management System) is the manipulation and DataBase Management software System, it consists of a set of computer programs, manage and control the use of data resources, it is the core of the DataBase System, mainly to share data effective organization, Management and access to its basic features include the following aspects:
(1) data definition function: the structure of the database was described, including the model, model, the model definition; The integrity of the database definition; Security definitions (such as user password, level, access permissions). Access paths, such as indexes, such as the definition of
(2) data manipulation functions: the DBMS provides data manipulation language, users can use DML manipulation of data, implement the basic operation of the database, such as search, insert, delete and modify, DML has two kinds: one kind is the host language, one kind is self-supporting language,
(3) of the database operation management: in the database, use and maintenance of the database management system of unified management, unified control, in order to guarantee the security of data integrity, multi-user concurrent use of data and system recovery after failure occurs, thus ensuring the normal operation of the database system,
(4) data organization, storage and management functions: DBMS classification organization, various data storage and management, including data dictionary, user data, access paths, etc.,
(5) the database the establishment and maintenance of function: it includes database initial data input, transformation function, database dumps, restore function, database organization function and performance monitoring, analysis function and so on,
6. Other features: the DBMS and other software system in the network communication function, or file system between the DBMS data conversion function; Visits and interoperability between heterogeneous database functions, such as
ADO interactions with the database technology
ADO is independent of the development tools and development language data Access interface, it provides the application developer, the ability of real-time Access to all kinds of database application, you can easily complete to each kind of database query, Access operations, such as ADO general data Access (UDA), also known as the data source including the database, email, files, text, graphics, etc., not only can use ADO to read Access and SQL Server database, can also read other compatible with ODBC database, ADO steps to the operation of the database is generally divided into the following steps:
1) create the data source name (DSN);
(2) create a database Connection (Connection);
3. Create a database object;
(4) operation database;
5. Close the database objects and connection,
The MySQL database
MySQL is a small relational database management system, developers for Sweden MySQL AB company, MySQL is widely used in small and medium-sized websites on the Internet, because of its small volume, quick speed, low total cost of ownership, especially the feature of open source, many small and medium-sized websites in order to reduce the total cost of ownership website and chose the MySQL database as web site,
SQL is a standardized language, it makes the storage, update and access information more easily, for example, you can use the SQL language is a web site to retrieve product information and store customer information, also fast and flexible enough to allow for your MYSQL storage record file and image,
MYSQL main goal is fast, robust and easy to use, MYSQL is founded has been used in high demand the production of a set of practical routine for many years, although the MYSQL is still in development, but it has to provide a rich and extremely useful feature sets,
MYSQL's main characteristics are as follows:
1) fully multi-threaded, suitable for CPU usage,
2) provide C, C + +, JAVA (JDBC), Perl, Python, PHP and TCL API interface,
More than 3) platform, including: Solaris, SunOS, BSDI, SGI, IR - IX, AIX, DEC, UNIX, Linux, FreeBSD, SCO OpenServer, NetBSD, OpenBSD, HPUX, Win9x and NT. (all the function of the support is not the same),
4) various types of data, including:/unsigned 1 byte,2,3,4,8 INT, FLOAT, DOUBLE, CHAR, VARCHAR, TEXT, LOB, the DATE and DATETIME, YEAR, SET, ENUM,
5) is very flexible and security permissions system, password encryption,
6) provide Win9X ODBC interface, through the Access to, and another third party developers to provide variety of ODBC driver,
7) can deal with large data (more than 50 million records), table size is limited to the OS file size: Linux is 2 g, Solaris 2.5.1 for 4 g, Solaris 2.6 for 1000 g,
8) by the commercial software memory leak testing authority without memory leaks,
9) a variety of language support,
Web technology
Web technology overview
The rapid development of Web technology, enables all mankind to share all kinds of resources on the Web, including the powerful computing resources, huge amounts of information database resources, a variety of multimedia information resources, all kinds of software tools, resources, etc., which makes anyone can at any time, any place and any device to obtain needed information resources,
Essentially Web technology is the integration and integrated application of various techniques, it is based on TCP/IP protocol, using HTML description of network resources, through the Hypertext (Hypertext), Hypermedia Hypermedia technology to realize the hyperlink, regardless of the text, graphics, animation, sound can through the link to the files on the server to other documents or other sites, enable customers to interact with search needed information quickly and through a form for users to fill out and submit to database by the server application, such as
Since the generation of the Web, Web technology has expanded from the original simple document browsing to today's complex e-commerce applications, during which experienced static documents, dynamic interactive pages and scalable real-time transaction processing three phases,
From static to dynamic technology, from the development platform to application model, from the traditional Web to the semantic Web, the Web has experienced the technology wave of again and again, also face more serious technical challenges, the main characteristic of Web 1.0 is that users obtain information from the browser, and Web 2.0, is more pay attention to the interaction of the user, the user is not only the consumer site content (browsers), is also a maker of website content, mainly including: the BLOG (BLOG), RSS, encyclopedia (Wiki), key, social networks (SNS) and peer-to-peer (P2P), instant messaging (IM), intelligent search engine, such as
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