Unified State Exam in Informatics. Solving tasks C1. material for preparing for the exam (GIA) in informatics and ICT (grade 11) on the topic. Everything you need to know about the exam in computer science Usefulness for the binary number system

The lesson considered the solution 1 task of the exam in informatics 2017: a detailed explanation and analysis of tasks is given

The 1st topic is characterized as tasks of the basic level of complexity, the execution time is about 1 minute, the maximum score is 1

Number systems and presentation of information in PC memory

To solve 1 task, you should remember and repeat the following topics:

Binary number system

Number of digits or base of the system: 2
Numbers (alphabet): 0, 1

Translation of numbers from the 10th system. count-i to binary

Translation of numbers from the 2nd system. mid at 10th

When dealing with large numbers, it is better to use:

Expansion in powers of two

Octal number system

8
Numbers (alphabet): 0, 1, 2, 3, 4, 5, 6, 7

Translation of numbers from the 10th system. mid at 8th

Translation of numbers from the 8th system. mid at 10th

Translation of numbers from the 8th system. midpoint to 2nd and back in triads

Translation from the 8th system. midpoint to 2nd and back in triads

Hexadecimal number system

Number of digits or base of the system: 16
Numbers (alphabet): 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A (10), B (11), C (12), D (13), E (14), F (15)

Translation from the 10th system. mid at 16

Conversion from the 16th numeral system to the 10th

Translation from the 16th system. mid at 10th

Translation of numbers from the 2nd system. midpoint to 16th and back in tetrads

Translation from 2nd p. midpoint to 16th and back in tetrads

Utility for the binary number system:

• numbers that end in 2-numbered notation 0 - even, on 1 - odd;
• respectively, numbers that are divisible by 4 , will end in 00 , etc.; thus we derive general rule: numbers that are divisible by 2 k end in k zeros
• if the number N is in the interval 2 k-1 ≤ N, its binary notation will contain exactly k digits, for example, for 126 :

• need to translate a-1 in the binary number system;
• do bit inversion: replace all zeros with ones and ones with zeros within the bit grid

Solution 1 of the exam task

1_1: Analysis of 1 task of the Unified State Exam in Informatics 2017 FIPI option 1 (Krylov S.S., Churkina T.E.):

how many units in binary notation hexadecimal 2AC1 16?

• In hexadecimal c-me, numbers from 10 before 15 represented by letters of the Latin alphabet: A-10, B-11, C-12, D-13, E-14, F-15.
• It is necessary to remember the binary codes of numbers from 1 before 15 (see the theory above on the page), since to translate hexadecimal into binary c-mu, it is enough to write each digit separately as a four of binary digits (tetrad):

Result: 6

Detailed analysis of 1 task with an explanation, watch the video:

1_2: 1 task. Demo version of the Unified State Exam 2018 Informatics (FIPI):

How many integers are there x for which the inequality 2A 16<x<61 8 ?
In the answer, please indicate only the number of numbers.

• Converting 2A 16 in Decimal number system:

Result: 6

For a detailed solution to this 1 task from the 2018 USE demo, see the video:

1_3: 1 task. GVE Grade 11 in Informatics 2018 (FIPI):

How many significant digits are there in binary notation of a decimal number 129 ?
1) 6
2) 2
3) 7
4) 8

• Let's translate from decimal s-we number to binary by dividing by 2 , on the right we will write the remainders:

Result: 4

1_4: Solution 1 of the USE task in informatics (control version of the examination paper in 2018, S. S. Krylov, D. M. Ushakov):

How many natural numbers x exist for which the inequality

101011 2 ?

In the answer, please indicate only the number of numbers.

Result: 17

For a detailed analysis of the solution to the training option, we suggest watching the video:

1_5: Analysis of 1 task of the exam, option No. 1, 2019 Informatics and ICT Typical examination options (10 options), S.S. Krylov, T.E. Churkina ::

Evaluate the value of the expression AE 16 - 19 16.
In your answer, write down the calculated value in decimal notation.

• Let's translate the reduced and subtracted in the decimal number system:

* A 16 corresponds to 10 in decimal notation

* E 16 corresponds to 14 in decimal notation

1 0 19 = 1*16 1 + 9*16 0 = 16 + 9 = 25

Result: 149

1_6: Analysis of 1 task of the exam (from the site of K. Polyakov, option 104 with reference to Noskin A.N.):

Petya and Kolya guess natural numbers. Petya thought of a number NS, and Kolya's number Have... After Petya added to Kolya's number 9 , and Kolya to Petya's number 20 , the sum of the obtained numbers when written in the binary number system is five units.

What is equal to original amount the numbers the boys thought of? Write the answer in binary notation. It is not necessary to indicate the reason.

• Let's rewrite the problem statement in a more understandable form:

Result: 10

1_7: Analysis of 1 task of the exam (from the site of K. Polyakov, option 105 with reference to Kutsyr E.V.):

Please indicate largest four-digit octal number, quaternary whose record contains exactly 2 triplets, not standing next to... In the answer, write down only the octal number itself; you do not need to indicate the base of the number system.

• Recall that in the octal system, the maximum digit is 7, and in the quaternary system - 3. Let's try to translate the largest octal number into the quaternary system, disregarding the condition with non-standing triplets in a row. Let's translate using the binary number system:

Result: 7352

1_8: Analysis of 1 task of the exam (from the site of K. Polyakov, option 109 with reference to Noskin A.N.):

A segment is set ... Number a- the smallest number, octal whose record contains exactly 3 characters one of which is 3 ... Number b – least number, hexadecimal whose record contains exactly 3 characters one of which is F.

Define number of natural numbers on this segment ( including its ends).

• Let's rewrite the problem statement in a more understandable form, substituting the values ​​for the numbers a and b:

Result: 205

1_9: Solution 1 task of the exam 2020 (Thematic training tasks, 2020, Samylkina N.N., Sinitskaya I.V., Soboleva V.V.):

One byte is used to store a signed integer.

How many units does the internal representation of a number contain ( -116 )?

To convert a negative number to a binary number system, we will use the following algorithm:
• Subtract one from the module of the original number:

Result: 10001100

Today we will analyze the theoretical aspect of 1 task from Unified State Exam in Informatics... In this task, you need to be able to translate numbers from different number systems to others. The main number systems are: binary, octal, decimal (our native) and hexadecimal.

Converting numbers from the binary system to the hexadecimal number system.

First you need to write the following table for yourself in a draft:

Let's take a look at this table. The first column contains numbers from 0 to 15 in our native decimal notation. In the second column there are also numbers from 0 to 15, but already in the binary system, and in the third also from 0 to 15 in the hexadecimal number system.

Writing the numbers from 0 to 15 in our native decimal system is no problem for anyone.

Binary numbers are best written according to the following rule: in the least significant bit we alternate zero and one, in the next bit the alternation of zeros and ones is twice as slow (two zeros, two ones, two zeros, etc.), in the next bit the alternation is twice as slow (4 zeros, 4 ones, etc.) and finally 8 zeros and 8 ones - in the most significant bit.

In the hexadecimal number system, in addition to our usual characters from 0 to 9, the symbols A, B, C, D, E, F are invented, and from these 16 characters (from 0 to 15) any number is compiled, just as in our system any number is compiled of ten digits (from 0 to 9). Accordingly, to count from 0 to 15, you need to iterate over all the characters that are in the hexadecimal system (from 0 to F).

Now let's look at how to use this table to convert from binary to hexadecimal. Let's translate the number 100101000 from binary to hexadecimal.

To complete this task, it is necessary to split our binary number into 4 digits starting from the right edge, and each 4 digits must be found in our table: 1000 - this will be 8, 0010 - 2, 0001 - this is 1. In the most significant bit we have there is only one unit left, we supplemented it with 3 zeros.

Means the number 100101000 2 in binary system will be 128 16 in hexadecimal.

Converting numbers from binary to octal
number system.

Binary to Octal X 2 -> X 8 we translate in the same way, only now we take from the table not four digits, but three numbers.

Thus, the number 1001111001 2 in the binary system will be equal to 1171 8 in octal system.

Converting numbers from hexadecimal to binary
number system.

We do exactly the same as when converting numbers from binary to hexadecimal, but in the opposite order. We look at the table: D - 1101, F - 1111, 4 - 0100. It turns out the number 010011111101. On the left, we discard the zeros 10011111101 .

4FD 16 -> 10011111101 2.

Converting numbers from octal to binary
number system.

We proceed as we did earlier. We split each digit of the octal system into 3 digits of the binary system, using the table that is given at the beginning of the article. We discard the zeros on the left.

347 8 -> 11100111 2 .

Converting numbers from binary to decimal
number system.

Let's translate the number:

We take the digits of a binary number, starting with the least significant bit (i.e. on the right), and start multiplying by two to the appropriate power. The degree starts from zero and each time increases by 1. All these products are summed up.

After calculating, we get the number in decimal system:

Result 11010011 2 -> 211 10

Converting numbers from decimal to binary
number system.

Let's see how to convert from decimal to binary. Let's take the number 213 .

Converting numbers from hexadecimal to octal
reckoning and vice versa.

Let's translate the number A10 hex to octal A10 16 -> X 8.

We split each digit of the hexadecimal code into 4 digits of the binary code from the table at the beginning of the article (that is, we translate the number into the binary system). Divide the resulting number into three digits - and collect the number already in the octal system - as shown in the figure. We translate back in the same way, only in reverse order.

Converting numbers from hexadecimal to decimal
number system.

Let's translate the number 5B3 from hexadecimal to decimal 5B3 16 -> X 10.

We act in exactly the same way as when converting from binary to decimal, only we multiply the numbers by 16 to the appropriate power. Letters turn into decimal numbers from the table. We start, as always, on the right, i.e. from the least significant digit.

Converting numbers from decimal to hexadecimal
number system.

Let's translate the number 203 decimal to hexadecimal 203 10 -> X 16

Divide the number by 16 until you get a number from 1 to 15. Write the remainders in reverse order. The numbers from 10 to 15 are converted into numbers.

Converting numbers from octal to decimal
number system.

Let's translate the number 347 octal to decimal 347 8 -> X 10

We do it similarly to the previous examples, only now we multiply by 8 to the appropriate power.

Converting numbers from decimal to octal
number system.

We do it in the same way as in the previous examples.

Happy exams!

For effective training in computer science, for each assignment, a brief theoretical material is given to complete the task. Selected over 10 training tasks with analysis and answers, developed on the basis of demo versions of previous years.

There are no changes in the KIM USE 2020 in informatics and ICT.

Areas of knowledge testing:

• Programming;
• Algorithmization;
• ICT tools;
• Information activity;
• Information processes.

Action to be taken when preparing:

• Repetition of the theoretical course;
• Solution tests in informatics online;
• Knowledge of programming languages;
• Improve mathematics and mathematical logic;
• To use a wider range of literature - the school curriculum is not enough for success on the exam.

Exam structure

The duration of the exam is 3 hours 55 minutes (255 minutes), one and a half hours of which it is recommended to devote to the tasks of the first part of the CMMs.

Tasks in tickets are divided into blocks:

• Part 1- 23 tasks with a short answer.
• Part 2- 4 problems with a detailed answer.

Of the proposed 23 tasks of the first part of the examination work, 12 relate to the basic level of knowledge testing, 10 - of increased complexity, 1 - of a high level of complexity. Three tasks of the second part of a high level of complexity, one - of an increased level.

When making a decision, it is obligatory to record a detailed answer (free form).
In some tasks, the text of the condition is presented in five programming languages ​​at once - for the convenience of students.

Points for Computer Science Assignments

1 point - for 1-23 tasks
2 points - 25.
3 points - 24, 26.
4 points - 27.
Total: 35 points.

For admission to a middle-level technical university, you must score at least 62 points. To enter the capital's university, the number of points must correspond to 85-95.

To successfully write the exam paper, you must have a clear command of theory and constant practice in solving tasks.

Your formula for success

Work + work on mistakes + carefully read the question from beginning to end in order to avoid mistakes = maximum score on the exam in computer science.

Secondary general education

Computer science

Assignment 1 of the exam-2019 in informatics: theory and practice

What's new?

In the upcoming USE, there have been no changes compared to last year.

Read about innovations in exam options in other subjects in.

The manual contains tasks that are as close as possible to the real ones used on the exam, but distributed by topics in the order of their study in grades 10-11 of high school. Working with the book, you can consistently work out each topic, eliminate gaps in knowledge, and also systematize the material being studied. This structure of the book will help you prepare more effectively for the exam.

Demo-KIM USE-2019 in informatics has not undergone any changes in its structure compared to 2018. This greatly simplifies the work of the teacher and, of course, the already built (I would like to count on) plan for preparing the student for the exam.

We will consider the solution of the proposed project (at the time of this writing - still a PROJECT) KIM USE in informatics.

Part 1

Answers to tasks 1–23 are a number, a sequence of letters or numbers that should be written in ANSWER FORM № 1 to the right of the number of the corresponding task, starting from the first cell, without spaces, commas and other additional symbols. Write each character in a separate box in accordance with the samples given in the form.

Exercise 1

Evaluate the value of the expression 9E 16 - 94 16.

In your answer, write down the calculated value in decimal notation.

Answer: ___________________________.

Solution

Simple Hexadecimal Arithmetic:

Obviously, the hexadecimal digit E 16 corresponds to the decimal value 14. The difference between the original numbers gives the value A 16. The solution, in principle, has already been found. Following the condition, we represent the found solution in the decimal number system. We have: A 16 = 10 10.

Which programming language to choose, what tasks to focus on and how to allocate time on the exam

Teaches computer science at Foxford

Different universities require different IT entrance exams. Somewhere you need to pass physics, somewhere - computer science. It is up to you to decide which exam to prepare for, but it should be borne in mind that the competition for the specialty where you need to take physics is usually lower than for the specialties where the Unified State Exam in computer science is required, i.e. the likelihood of entering "through physics" is greater.

Why then take the Unified State Exam in Computer Science?

• It is faster and easier to prepare for it than for physics.
• You will be able to choose from more specialties.
• It will be easier for you to study in the chosen specialty.

What you need to know about the exam in computer science

The Unified State Exam in Informatics consists of two parts. In the first part there are 23 problems with a short answer, in the second - 4 problems with a detailed answer. The first part of the exam contains 12 basic-level assignments, 10 advanced-level assignments and 1 high-level assignment. In the second part - 1 task of an advanced level and 3 - a high one.

Solving problems from the first part allows you to score 23 primary points - one point for the completed task. Solving the problems of the second part adds 12 primary points (3, 2, 3 and 4 points for each problem, respectively). Thus, the maximum primary points that can be obtained for solving all tasks is 35.

Primary scores are converted to test scores, which are the result of the exam. 35 primary points = 100 test points for the exam. At the same time, more test points are awarded for solving problems from the second part of the exam than for answering the problems of the first part. Each primary score obtained in the second part of the exam will give you 3 or 4 test points, which in total is about 40 final points for the exam.

This means that when completing the Unified State Exam in Informatics, it is necessary to pay special attention to solving problems with a detailed answer: No. 24, 25, 26 and 27. Their successful completion will allow you to gain more final points. But the cost of an error during their implementation is higher - the loss of each primary point is fraught with the fact that you will not pass the competition, because 3-4 final points for the Unified State Exam with high competition in IT specialties can become decisive.

How to Prepare for Part One Challenges

• Pay special attention to tasks No. 9, 10, 11, 12, 15, 18, 20, 23. These tasks, according to the analysis of the results of the past years, are especially difficult. Difficulties with the solution of these problems are experienced not only by those who have a low overall score for the Unified State Exam in computer science, but also "good" and "excellent" students.
• Memorize the table of powers of number 2.
• Remember that Kbytes in tasks means Kibybytes, not Kilobytes. 1 kibyte = 1024 bytes. This will help avoid calculation errors.
• Carefully study the options for the USE from previous years. The computer science exam is one of the most stable, which means that you can safely use the USE options for the last 3-4 years for preparation.
• Get to know the different options for the wording of the tasks. Remember that minor wording changes will always result in poor exam scores.
• Read the problem statement carefully. Most of the errors in completing assignments are associated with a misunderstanding of the condition.
• Learn to independently check the completed tasks and find errors in the answers.

What you need to know about solving problems with a detailed answer

24 task - to find an error

25 task requires drawing up a simple program

Problem 26 - on game theory

27 task - it is necessary to program a complex program

The main difficulty in the exam is 27 problems. It can only be solved60-70% of those writing the exam in computer science. Its peculiarity lies in the fact that it is impossible to prepare for it in advance. Every year a fundamentally new problem is presented for the exam. When solving problem # 27, not a single semantic error should be allowed.

How to time your exam

Focus on the data that are given in the specification of control measuring materials for the exam in informatics. It indicates the approximate time allotted for completing the tasks of the first and second parts of the exam.

The exam in computer science lasts 235 minutes

Of these, 90 minutes are devoted to solving problems from the first part. On average, each task from the first part takes 3 to 5 minutes. It takes 10 minutes to solve problem 23.

There are 145 minutes left to solve the tasks of the second part of the exam, while solving the last problem # 27 will take at least 55 minutes. These calculations were carried out by specialists from the Federal Institute for Pedagogical Measurements and are based on the results of past exams, so they should be taken seriously and used as a guide for the exam.

Programming languages ​​- which one to choose

1. BASIC. It is an outdated language, and although it is still being taught in schools, there is no point in wasting time mastering it.
2. School algorithmic programming language. It is designed specifically for early learning in programming, convenient for mastering the initial algorithms, but practically does not contain depth, there is nowhere to develop in it.
3. Pascal. It is still one of the most common programming languages ​​for teaching in schools and universities, but its capabilities are severely limited. Pascal is quite suitable as a writing language for the exam.
4. C ++. A universal language, one of the fastest programming languages. It is difficult to learn from it, but in practical application its possibilities are very wide.
5. Python... It is easy to learn at an elementary level, the only thing that is required is knowledge of the English language. At the same time, with an in-depth study of Python, it provides the programmer with no less opportunities than C ++. Having started learning "Python" at school, you will use it in the future, you do not have to relearn to another language in order to reach new horizons in programming. To pass the exam, it is enough to know "Python" at a basic level.

Good to know

• Informatics works are evaluated by two experts. If the experts' assessment results differ by 1 point, the higher of the two points is assigned. If the discrepancy is 2 points or more, the work is rechecked by a third expert.
• A useful site for preparing for the exam in computer science -