1. information structures, stored in external memory
2. software that allows you to organize information in the form of tables,
3. software tools that process tabular data,
4. software tools that search for information,
5. information structures stored in the OP.

2. The most common in practice are:

1. distributed databases data;
2. hierarchical databases;
3. network databases;
4. relational databases.

3. What are the forms for?

1. for storing database data;
2. for selecting and processing database data;
3. to enter database data and view it;
4. For automatic execution groups of commands;
5. to perform complex program actions?

4. A distributed database is a database

1. stored on one computer.
2. different parts of which are stored on many computers,interconnected by a network.

5. The button indicates

1. sorting records in ascending order;
2. sort records in descending order;
3. displaying records starting with these letters;
4. counting the number of records in the database

6. Does a table that does not have any records contain any information?

1. an empty table does not contain any information;
2. an empty table contains information about the database structure;
3. an empty table contains information about future records;
4. a table without records cannot exist.

7. What is the purpose of the “table” object?

1. for data storage
2. for data archiving
3. to enter and delete data
4. for data sampling

8. A fragment of the database provides information about family relationships. Based on the given data, determine the surname and initials of grandmother Ivanova A.I.

Table 1

Table 2

1. Tseys T.N.
2. Petrenko A.I.

c) Chernykh I.A.

d) Petrenko N.N.

9. The database structure will change if

1. add/delete record;
2. add/remove field.
3. edit entry;
4. swap entries;

1. to destroy unnecessary records
2. to find the information you need
3. to make new entries
4. to display the necessary information on the screen

11. What is special about the counter data type?

1. used to enter integers and real numbers
2. tends to automatically increase
3. has the property of automatic recalculation when deleting a record
4. used to enter fonts

12. Determine the database type:

1. Relational b) Hierarchical c) Network

13. The database contains information about school students: last name, class, test score, practical task, total points. What type of field should the TOTAL POINTS field be?

1. symbolic b) logical c) numeric d) any type e) Date

14. How many records are there in the database?

There are many database management systems in the world. Although they may work differently with different objects and provide the user with different functions and features, most DBMSs rely on a single, established set of core concepts. This gives us the opportunity to consider one system and generalize its concepts, techniques and methods to the entire class of DBMS. As such a training object, we chose the Microsoft Access DBMS, which is included in Microsoft package Office.

Access 1.0, released in 1992, was one of the most remarkable products ever developed for personal computers. This package set new standards for the interface, improving the reporting system and increasing the speed of data management. Thanks to this, it has become the most popular DBMS package for Windows and the only universal software product that satisfies everyone - both end users and developers of full-scale applications. Currently, Access 97 and Access 2000 versions are widely used.

When developing databases, you have to work with several different structural objects at the same time. Access has implemented a completely new data storage format. A single unified structure, called a container, includes all structural elements - tables, queries, software modules on Access Basic, etc. The standard extension of these files is .MDB (Microsoft Data Base). When you open a .MDB file, all database objects are listed in the database window. To select one of the specified lists, use the tabs (spines).

Let's briefly look at the purpose of Access objects.

Table designed to store data in the form of records (rows) and fields (columns). Tables form the basis of a database. They store information organized in a certain way.

Request – allows you to obtain the necessary data from one or more tables and calculate the values ​​of some data using formulas.

Form – an object intended for both input and output of data in a user-friendly form. The form can contain controls used to enter, display, and change data in table fields.

Report – an object intended for printing data.

Macros – tools for automating work with forms, reports, etc.

Modules are software modules written in Visual Basic.

Rice. 7. Database window in Access.

Tables

The main structural element of Access is a table in which information is stored. All other objects are based on table data. Like other databases, Access uses the terms field(table column) and recording(table row). Each field has its own type and has certain properties.

Field properties determine which types of data can be entered into a field and which cannot, as well as what can be done with the data contained in the field.

Field types

Text- used to store text information up to 255 characters long.

Memo- used to store large text up to 65,535 characters. The peculiarity of the MEMO field is that this data is actually stored not in the field, but in another place, and only a pointer to where the text is located is stored in the field.

Numerical- used to store numeric values ​​that can be used in mathematical calculations. It also has a size, but the number fields are different, for example, for entering integers and for entering real numbers. In the latter case, in addition to the field size, the size of the decimal part of the number is also specified.

Date/Time- values ​​are entered into fields of this type in a standard format, for example 1/1/99, 12:53:00 PM.

Monetary- designed to store the exact value of very large numbers and allow precise calculations on them. Monetary amounts can also be stored in a numeric field, but it is more convenient to work with them in a monetary format. In this case, the computer displays numbers together with monetary units, distinguishes between rubles and kopecks, pounds and pence, dollars and cents.

Counter- used for automatic numbering of the added record. At first glance, this is an ordinary numeric field, but it has the property of automatic growth. If the database has such a field, then when entering new entry a number is automatically entered into it, one greater than the value of the same field in the previous record.

Logical- used to store logical quantities that have only two values ​​(Yes or No; 0 or 1; True or False, etc.). The length of such a field is always 1 bit.

OLE object- allows you to store documents, tables, graphs, drawings, audio signals, video and other information created Windows applications, which support OLE technology.

Substitution Wizard.. - this field is used to create connections between Access DBMS tables.

Fields are unique and key . Creating a database always begins with developing the structure of its tables. The structure should be such that when working with the database you need to enter as little data as possible into it. If entering some data has to be repeated several times, the database is made of several related tables. The structure of each table is developed separately. In order for connections between tables to work reliably, and for a record from one table to be able to unambiguously find records in another table, it is necessary to provide unique fields in the table. Unique field is a field in which values ​​cannot be repeated. If the data in the field is repeated and a message must be issued about this, then there is a concept for this key field.

An integral part of most database tables is the “Counter” field. What is the peculiarity of this column, what functions it performs and what properties it has, we will consider below. To do this, let us dwell in more detail on the concepts of databases, their objects and, in particular, tables, the element of which is the counter.

Databases

Let's take a short excursion into database computer science. A database is a set of tables with information between which there are connections. Databases are convenient for storage large quantity data related to one topic. Businesses use databases to store information about clients: names, dates of birth, address, passport and other personal data.

For each client, a record of orders is kept: product and its quantity, dates, delivery method, and other features. The information about the products itself is also contained in repositories and represents a complete set of parameters characterizing the products for sale.

Banks store information about clients, deposits and loans. It also contains financial parameters that allow you to generate reports for business analysis and submission to regulatory authorities.

A travel company works with a database that stores data about business partners, tourists, hotels and excursions. With the help of special applications, tariffs and costs of tours are calculated.

Thus, the data contained in the database corresponds to the industry in which the company operates.

Database objects

The main database object is a table, the main storage of database information. These are the tables that we are used to seeing in classes at school or university, in books and textbooks. They consist of rows, which in databases are called records or tuples, and columns, called fields.

Queries perform the main work of interacting interface forms with other database objects, their elements and the database itself. When you simply click the Delete Row button on the DB application form, it is the query that completes the action and fulfills your requirement.

Reports are used to output information to the printer, and macros and modules are provided in the database application interface to perform procedures in response to events.

Features of database tables

As we know from the computer science course, databases consist of tables. Each row contains data related to one object. Let's give an example. The travel agency database contains a table “Hotels”, each entry of which contains full information for one of the hotels: name, category, address, link to website, telephone and fax number, etc.

Each column defines exactly what values ​​are contained in it. From the same example of hotels, you can see that one of the fields is called “Name”, and it contains only the names of the hotels. Another field is the category, which records how many stars this hotel has. Thus, going through the entire column, we see the values ​​of one parameter for each of the rows.

Database fields have various types: text, numeric, monetary, logical, date and time format. This defines the restrictions that are placed on the values ​​in these columns. Having defined the “Date and Time” field type, we will no longer be able to enter a last name or first name into it, entering alphabetic characters in a numeric field is prohibited, and it is impossible to enter a cost in a logical column.

The “Counter” field type stands out. What is the peculiarity of its use, we will consider below.

Field type "Counter"

Let's look again at our hotel table. In the first column, which is called “Code”, we see numbers - serial numbers of each of the hotels. They are not repeated and designate the entry in such a way that we know exactly under which number this or that hotel is contained in the table. This helps you easily find the desired hotel using this code.

The "Code" field has the "Counter" field type. What is special about this field based on the information above? First of all, this is the uniqueness of the column values. This property ensures unique record identification. The table cannot have two records with the same value for the “Code” parameter. The uniqueness of the field's values ​​allows it to be used as a primary key, that is, a column that is referenced by fields in other tables.

Another ability of the counter is auto-increment - the property of automatically increasing the number. Thanks to it, the user does not need to think about what number to enter for the next entry. The system itself will increase the number of the previous one and assign this number to the new one.

Example

The “Hotels” table has been added to our experimental Access database. The counter field is called “Code”, numbering starts from one.

The second table of the database - “Regions” - also contains a counter field. What is special about the region table? The fact is that its records are used by the hotel table to specify the location of the hotel. Here the value is selected from the dropdown list:

And by region we can see the hotels located there:

Thus, the counter field is a significant element of database tables that allows you to uniquely identify a record, automatically assign it a unique number, and then use this number when referring to rows of an object from another table.

Electricity meters first appeared in the 19th century. Their appearance was associated with massive research into electromagnetism conducted by scientists and their inventions powered by electricity. Infrastructure developments and debates over consumer choice of DC or AC led to the discovery of the transformer, and attempts to account for AC electrical energy fueled breakthrough innovation. In 1888, Oliver B. Shellenberger developed the first alternating current meter.

Operating principle and design of the electricity meter

To take into account the active electricity of alternating current, induction single-phase and three-phase devices are needed, and to account for direct current, which is used in electric transport, railways, etc. – electrodynamic counter.

The counting disk mechanism of the electric meter records the number of revolutions of its moving part, which is proportional to the amount of electricity consumed.

In an induction electric meter, the aluminum disk (the moving part of the device) rotates when electricity is consumed using eddy currents, which are induced by the magnetic field of the meter coil. Here the interaction of two fields occurs: the magnetic field of the eddy currents and the magnetic field of the coil. The meter is designed in such a way that for its operation two currents are created, one of which flows in a circuit parallel to the load, and the other in the circuit of the load current itself. Both of these currents flow in coils that are placed on cores made of iron. Their names are appropriate: “ampere coil” and “voltaic coil”. The iron cores of the coils are magnetized by alternating current. Using a variable electric current contributes to the fact that the poles of electromagnets are constantly changing. Due to this, the effect of passing a magnetic field between them occurs. The arrangement of the coils and the magnetic field between them is calculated so that they form eddy currents in the body of the disk, and the direction of these currents will induce the magnetic field to pull the disk along with it, creating rotation. The speed of rotation of the disk will be proportional to the magnitude of the currents in both coils, that is, the speed of rotation, based on practical calculations, will be directly proportional to the product of the cosine of the phase shift (power consumption) and the voltage U and current strength I. Using simple connecting techniques from mechanics, a rotating disk is connected to the digital readings of the device. The operating principle of an electronic type meter is that solid-state (electronic) elements are affected by voltage and alternating current, which leads to the creation of output pulses. The number of these pulses is proportional to the energy to be measured.

Types of electricity meters and their classification

There are several types and types of electricity meters, which differ in the type of measured values, design and type of connection. Meters are divided into devices that are directly connected to the power circuit and devices that are connected to the power circuit using special instrument transformers.

According to the type of design, electricity meters are divided into:

1. Induction (electromechanical) is an electric meter in which a moving element made of a conductive material is influenced by a magnetic field created by stationary current-carrying coils. The disk acts as a moving element. The magnetic field of the coils induces currents that flow through the disk. The amount of energy consumed is directly proportional to the number of revolutions of this disk.
2. Electronic (static) is an electric meter, the solid-state (electronic) elements of which are affected by alternating current and voltage, which creates pulses at the output, the number of which is equal to the amount of measured energy. In such meters, the measurement of active electricity is based on the fact that analog input signals of current and voltage are converted into a counting pulse.
3. A hybrid electric meter is a cross between devices with a digital interface and a measuring electronic or induction part, with a mechanical calculation device. Such devices are rare.

Meters can also be classified according to the measured values: single-phase - measure alternating current 220 volts, 50 Hz, as well as three-phase, designed to measure voltage of 380 V and a frequency of 50 Hz. In high-voltage circuits, where the voltage reaches 600 V, three-phase meters with current transformers are used, which measure electricity with a voltage of 100 V.

What is special about the counter data type?

Currently, electricity is accounted for mainly at one tariff. In this case, the cost of electricity is the same and does not depend on the time of its consumption. When installing an induction meter, electricity readings are reproduced using mechanical parts. This mechanical type of data has a certain degree of error, which affects the payment for electricity. Unlike induction meters, which do not allow for multi-tariff electricity calculations, electronic meters provide this opportunity.

The inter-verification period of electronic electricity meters ranges from 4 to 16 years.

In electronic meters, all readings are displayed on a liquid crystal display and have a digital data type, which practically eliminates all errors associated with mechanical effects on the device parts. Electronic meters will be an excellent solution for apartments where high energy consumption prevails, as well as for enterprises.

Electronic and mechanical household electricity meters

Household induction (mechanical) electricity meters, due to a number of shortcomings, are being forced out of the market by electronic meters. Mechanical electricity meters are used in apartments where energy consumption is low.

Disadvantages of induction meters:

• Inability to count more than one tariff;
• Lack of automatic remote reading function;
• Significant degree of error in accounting;
• Poor protection against electricity theft;
• Inconveniences associated with operation and installation;
• Low functionality.

The advantages of electronic meters include the ability to account for electricity at tariffs that are differentiated. That is, one-, two-, three-tariff and more meters have the ability to remember and display the amount of electricity consumed, taking into account the time periods that are programmed into them. Such multi-tariff accounting is implemented using a set of counting mechanisms operating at set time intervals corresponding to different tariffs.

The principle of operation and design of the electric meter (video)

In modern design of electrical systems, only electronic meters are used, because they have unlimited capabilities regarding service and are undeniable leaders in “information” terms.

>>Informatics 11th grade >>Informatics: Forums and their meanings. Robot rules for forums.

Practical work on the subject Computer Science 11th grade.

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DATABASES

TEST

1. Database is:

1. a set of data organized according to certain rules;
2. a set of programs for storing and processing large amounts of information;
3. interface that supports filling and manipulating data;
4. a certain set of information.

2. The most common in practice are:

1. distributed databases;
2. hierarchical databases;
3. network databases;
4. relational databases.

3. The most accurate analogue of a relational database can be:

1. unordered set of data;
2. vector;
3. family tree;
4. two-dimensional table.

4. Tables in databases are intended to:

1. for storing database data;

5. to perform complex program actions.

5. Which of the following is not an Access object:

1. modules;
2. tables;
3. macros;
4. keys;
5. shapes;
6. reports;
7. requests?

6. What are the requests for?

1. for storing database data;
2. for selecting and processing database data;
3. to enter database data and view it;
4. for automatic execution of a group of commands;
5. to perform complex program actions;
6. to output processed database data to a printer?

7. What are the forms for?

1. for storing database data;
2. for selecting and processing database data;
3. to enter database data and view it;
4. for automatic execution of a group of commands;

8. What are the modules for:

1. for storing database data;
2. for selecting and processing database data;
3. to enter database data and view it;
4. for automatic execution of a group of commands;
5. to perform complex program actions?

9. What are macros for:

1. for storing database data;
2. for selecting and processing database data;
3. to enter database data and view it;
4. for automatic execution of a group of commands;
5. to perform complex program actions?

10. In what mode does the user work with the database:

1. in design;
2. in amateur;
3. in a given;
4. in operational?

11. In which dialog box are connections between fields of database tables created:

1. table of connections;
2. connection diagram;
3. data schema;
4. data table?

12. Why, when closing a table, Access does not offer to save the entered data:

1. flaw in the program;
2. because the data is saved immediately after being entered into the table;
3. because the data is only saved after the entire database is closed?

13. Without which objects a database cannot exist:

1. without modules;
2. without reports;
3. without tables;
4. without forms;
5. no macros;
6. without requests?

14. In which table elements are database data stored:

1. in the fields;
2. in lines;
3. in columns;
4. in records;
5. in cells?

15. Does a table that does not have any records contain any information?

1. an empty table does not contain any information;
2. an empty table contains information about the structure of the database;
3. an empty table contains information about future records;
4. a table cannot exist without records.

16. Does a table that has no fields contain any information?

1. contains information about the structure of the database;
2. does not contain any information;
3. a table without fields cannot exist;
4. contains information about future entries.

17. What is special about the “counter” field?

18. What is special about the “memo” field?

1. serves to enter numerical data;
2. used to enter real numbers;
3. the data is stored not in the field, but in another place, and only a pointer to where the text is located is stored in the field;
4. has a limited size;
5. Has the property of automatic extension.

1. a field in which values ​​cannot be repeated;
2. a field that has a unique name;
3. a field whose value has the property of increasing.

20. Search keys in database management systems (DBMS) are called:

1. range of records in the database file in which the search is carried out;
2. logical expressions defining search conditions;
3. fields by the value of which the search is carried out;
4. numbers of records that satisfy the search conditions;
5. number of the first record in order that satisfies the search conditions?

KEY

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
1 4 4 1 4 2 3 5 4 4 3 2 3 5 2 3 5 3 1 3

Sent by the computer science teacher of the Specialized School No. 252 of the Obolonsky district of Kiev, O.I. Zhitinskaya.

Computer science for 11th grade free download, lesson plans, getting ready for school