program 3.Study the code carefully and write out the line where there is error, debug it and write out the correct code
1. ModuleModule1
2. Sub Main0
3. Dim num AsDouble
4. Num=10.0
5. Console.writeLine('The square root of '&num & "is"$Math.sqrt(num))
6. Console.ReadKey0
7. EndSub
8. EndModule​

Answers

Answer 1

Answer:

Several errors:

0 where ( ) was intended (probably OCR problem)space between As and DoubleSingle quote in stead of double quote in text string$ in stead of & near Math.sqrtmissing spaces around "is" for proper formatting

Program 3.Study The Code Carefully And Write Out The Line Where There Is Error, Debug It And Write Out

Related Questions

In order to print multiple worksheets, what needs to happen before printing?

Answers

Answer:

Explanation:

Click the File tab.

Click Print, or press the control p keyboard command.

On the Print screen, select the printer and other settings.

Click Print.

Discuss the DMA process​

Answers

Answer:

Direct memory access (DMA) is a process that allows an input/output (I/O) device to send or receive data directly to or from the main memory, bypassing the CPU to speed up memory operations and this process is managed by a chip known as a DMA controller (DMAC).

Explanation:

A defined portion of memory is used to send data directly from a peripheral to the motherboard without involving the microprocessor, so that the process does not interfere with overall computer operation.

In older computers, four DMA channels were numbered 0, 1, 2 and 3. When the 16-bit industry standard architecture (ISA) expansion bus was introduced, channels 5, 6 and 7 were added.

ISA was a computer bus standard for IBM-compatible computers, allowing a device to initiate transactions (bus mastering) at a quicker speed. The ISA DMA controller has 8 DMA channels, each one of which associated with a 16-bit address and count registers.

ISA has since been replaced by accelerated graphics port (AGP) and peripheral component interconnect (PCI) expansion cards, which are much faster. Each DMA transfers approximately 2 MB of data per second.

A computer's system resource tools are used for communication between hardware and software. The four types of system resources are:

   I/O addresses    Memory addresses.    Interrupt request numbers (IRQ).    Direct memory access (DMA) channels.

DMA channels are used to communicate data between the peripheral device and the system memory. All four system resources rely on certain lines on a bus. Some lines on the bus are used for IRQs, some for addresses (the I/O addresses and the memory address) and some for DMA channels.

A DMA channel enables a device to transfer data without exposing the CPU to a work overload. Without the DMA channels, the CPU copies every piece of data using a peripheral bus from the I/O device. Using a peripheral bus occupies the CPU during the read/write process and does not allow other work to be performed until the operation is completed.

With DMA, the CPU can process other tasks while data transfer is being performed. The transfer of data is first initiated by the CPU. The data block can be transferred to and from memory by the DMAC in three ways.

In burst mode, the system bus is released only after the data transfer is completed. In cycle stealing mode, during the transfer of data between the DMA channel and I/O device, the system bus is relinquished for a few clock cycles so that the CPU can perform other tasks. When the data transfer is complete, the CPU receives an interrupt request from the DMA controller. In transparent mode, the DMAC can take charge of the system bus only when it is not required by the processor.

However, using a DMA controller might cause cache coherency problems. The data stored in RAM accessed by the DMA controller may not be updated with the correct cache data if the CPU is using external memory.

Solutions include flushing cache lines before starting outgoing DMA transfers, or performing a cache invalidation on incoming DMA transfers when external writes are signaled to the cache controller.

Answer:

See explanation

Explanation:

DMA [tex]\to[/tex] Direct Memory Access.

The peripherals of a computer system are always in need to communicate with the main memory; it is the duty of the DMA to allow these peripherals to transfer data to and from the memory.

The first step is that the processor starts the DMA controller, then the peripheral is prepared to send or receive the data; lastly, the DMA sends signal when the peripheral is ready to carry out its operation.

A _______ read inputs the first data item from a file. It typically appears immediately before the loop that processes the data from the file and inputs the remaining data from the file.

Answers

Answer:

the answer is priming read

Explanation:

hope it helps u

Where does change management play a major role in transforming a client
business into a data-driven, intelligent enterprise?

Answers

To manage a modern IT environment characterized by hybrid complexity and exponential data growth — and to make that same IT a driver of growth and innovation for the business — you need to build intelligence into every layer of your infrastructure.

Change management plays a major role in transforming a client  business into a data-driven, intelligent enterprise in: data culture and literacy.

Data culture and literacy refer to all the processes involved in analyzing and understanding data within the framework of an organization.

The employees within such organizations are trained to read and understand data. It becomes a part of the organization's culture.

So data culture and literacy should be used when trying to transform a client  business into a data-driven, intelligent enterprise.

Learn more about data culture here:

https://brainly.com/question/21810261

Discuss the OSI Layer protocols application in Mobile Computing

Answers

Answer:

The OSI Model (Open Systems Interconnection Model) is a conceptual framework used to describe the functions of a networking system. The OSI model characterizes computing functions into a universal set of rules and requirements in order to support interoperability between different products and software.

Write a void function SelectionSortDescendTrace() that takes an integer array and sorts the array into descending order. The function should use nested loops and output the array after each iteration of the outer loop, thus outputting the array N-1 times (where N is the size). Complete main() to read in a list of up to 10 positive integers (ending in -1) and then call the SelectionSortDescendTrace() function. If the input is:

Answers

Answer:

Explanation:

The following program is written in Java. The main method asks the user to enter 10 different integer values. These values are saved to an integer array and passed to the SelectionSortDescendTrace() method. This method sorts the array in descending order while printing the entire array after every outer loop cycle. The program was tested and the output can be seen in the attached image below.

import java.util.*;

class Brainly {

   // Main Method

   public static void main(String[] args)

   {

       Scanner in = new Scanner(System.in);

       int[] myArr = new int[10];

       for (int i = 0; i < 10; i++) {

           System.out.print("Enter an integer: ");

           myArr[i] = in.nextInt();

           System.out.print('\n');

       }

       SelectionSortDescendTrace(myArr);

   }

   public static void SelectionSortDescendTrace(int[] myArr) {

       int temp;

       for (int i = 0; i < myArr.length; i++)

       {

           for (int j = 0; j <myArr.length; j++)

           {

               if (j != myArr.length - 1)

               {

                   if (myArr[j] < myArr[j + 1])

                   {

                       temp = myArr[j];

                       myArr[j] = myArr[j + 1];

                       myArr[j + 1] = temp;

                   }

               }

           }

           System.out.println(Arrays.toString(myArr));

       }

   }

}

Alexis received an email message from an unknown sender that included an attachment.

If she opens the attachment, what kind of malicious software might be activated, and what are the consequences?


Opening the attachment would release a worm, which would infect her system with a virus.


Opening the attachment would release a worm, which would infect her system with spyware.


Opening the attachment would release an active worm, which would infect her system with adware.


Opening the attachment would release a passive worm, which would infect her system with adware.

Answers

Answer:

Opening the attachment would release a worm, which would infect her system with a virus.

Answer:  B. Opening the attachment would release a worm, which would infect her system with a virus.

Instructions
Create a multimedia project that contains the text element and all the contents that you have studied about that element

Answers

Answer:

iiiio888887776558777u765

Arrays are commonly used to store data items. Arrays can be managed in ways that fill, iterate over, add to, and delete items from the array. Why is it useful to store multiple pieces of information?

Answers

Answer:

mark me brainlist

Explanation:

what are the functions of language in logic?​

Answers

Answer:

Three basic functions of language: Informative, Expressive, and Directive Language

Informative language. Simply put, informative language can be looked at as though it is either right or wrong, or true or falseExpressive languageDirective language

Is IBM 1041, Minicomputer? Yes or no​

Answers

Answer:

No

Explanation:

Mobile computing is growing in importance each and every day, and the IT manager must take that into account. Do some web research and develop a one-page description of the five most important things about HCI of mobile computing that the IT manager should know.

Answers

Answer:

phone grows everyday 82 percent

Explanation:

e) Point out the errors( if any) and correct them:-
class simple
{
inta,b,c;
double sumNumber
{
int d = a + b + c;
double e = d/5.6;
return e;
}
void show Number()
{
a = 10, b = 20, c=5;
System.out.println(d);
double f = sumNumber(a,b,c);
System.out.print(e);
}
}​

Answers

Explanation:

double e-d/5.6;is wrong it should return to c

explain the working principle of computer? can anyone tell​

Answers

Answer:

input process and output hehe

You have n warehouses and n shops. At each warehouse, a truck is loaded with enough goods to supply one shop. There are m roads, each going from a warehouse to a shop, and driving along the ith road takes d i hours, where d i is an integer. Design a polynomial time algorithm to send the trucks to the shops, minimising the time until all shops are supplied.

Answers

Following are the steps of the polynomial-time algorithm:

Split the routes according to their categorizationAssuming that mid = di of the middle road, low = road with the least di, and high = road with the highest di, we may do a binary search on the sorted list.All shops must be approachable only using these roads for every road, from low to mid.Check if all shops can be reached from[tex]\bold{ low \ to\ mid+1}[/tex] using only these roads.There is a solution if every shop can be reached by road only up to [tex]\bold{mid+1}[/tex], but not up to mid.You can [tex]\bold{set \ low = mid+1}[/tex] if all businesses aren't accessible using both [tex]\bold{mid\ and\ mid+1}[/tex] roads.If every shop could be reached using both mid and mid+1, then set high to mid-1.With these layouts of businesses and roads, no response can be given because [tex]\bold{ low > high}[/tex]You can do this by [tex]\bold{set\ mid = \frac{(low + high)}{2}}[/tex]The new low, mid, and high numbers are used in step (a).

In a minimum amount of time, this algorithm will determine the best strategy to supply all shops.

Learn more:

polynomial-time algorithm: brainly.com/question/20261998

explain computer coding in an understandable manner​

Answers

Answer:

Coding is simply how we communicate with computers. Code tells a computer what actions to take, and writing code is like creating a set of instructions

Explanation:

Computer coding empowers kids to not only consume digital media and technology, but to create it. Instead of simply playing videogame or envision what their own website, or app might look like and they'll have the outlet for the expression

Give examples of applications that access files by each of the following methods:
+ Sequentially.
+ Random.

Answers

Answer:

Explanation:

Usually, applications would have the capability of using either one of these options. But for the sake of the question here are some that usually prefer one method over the other.

Any program that targets an API usually uses Sequential access. This is because API's contain all of the data as objects. Therefore, you need to access that object and sequentially navigate that object to the desired information in order to access the data required.

A music application would have access to an entire folder of music. If the user chooses to set the application to randomly play music from that folder, then the application will use a Random Access method to randomly choose the music file to load every time that a song finishes.

T
N
O
?
You can insert only the row
only to
True or false

Answers

false

Explanation:

good luck bro

have a great day

Answer:

false

Explanation:

26. The
operator will cause a record to
be selected only if two or more
conditions are satisfied
In MS access

Answers

Answer:

AND

The  AND operator will cause a record to  be selected only if two or more

conditions are satisfied.

Fasilitas untuk pengaturan batas kertas pada Microsoft Word adalah….

a. Margin
b. View
c. LayOut
d. Paragraph

Office 92 sering disebut juga dengan….

a. Office 3.0
b. Office 7.0
c. Office Xp
d. Office 2.0


Answers

Fasilitas untuk pengaturan batas kertas pada Microsoft Word adalah

B.View

Office 92 sering disebut juga dengan

A.Office 3.0

What do you do if your computer dies/malfunctions? Reboot (Restart) Shut Down Recovery CD and Recover your system Call a person to fix it​

Answers

Answer:

Restart

Explanation:

Simply I may restart my pc if it dies/malfunctions. I'll not restart immediately, I'll wait for an hour and do restart my computer. If it doesn't work then maybe I'll Call a person to fix it.

Select the scenario that describes a top-down approach to data warehouse design.


Cathy’s Cards and Gifts, which has three stores, creates data marts for its sales, marketing, and delivery departments to study the possibility of establishing a new store.


Crawford's Fabrics, which wants to expand its operations, combines data from the purchasing and sales departments into a central database, to be divided into new data marts as needed.


Cynthia’s Florals, which is dealing with debt, creates new data marts for the service, delivery, and sales departments to develop a strategy to stay in business.


Connor’s Meat Market, which just opened, creates data marts to track the sale of each of the following meats: beef, pork, lamb, and fish.

Answers

Answer:

Crawford's Fabrics, which wants to expand its operations, combines data from the purchasing and sales departments into a central database, to be divided into new data marts as needed.

The scenario defines a top-down approach to data warehouse design as "Crawford's Fabrics, which wants to expand its operations, combines data from the purchasing and sales departments into a central database, to be divided into new data marts as needed".

What is a top-down approach to data warehouse design?

In the "Top-Down" method system, a data warehouse exists defined as a subject-oriented, time-variant, non-volatile, and integrated data storage for the entire business data from various sources exist validated, reformatted, and saved in a normalized (up to 3NF) database as the data warehouse.

Therefore, the correct answer is option b) Crawford's Fabrics, which wants to expand its operations, combines data from the purchasing and sales departments into a central database, to be divided into new data marts as needed.

To learn more about warehouse design

https://brainly.com/question/25885061

#SPJ2

What is the importance of using Onedrive in Windows 10 and how knowledge of it will have an impact in today's workplace?

Answers

The importance of one drive in windows 10 is that it helps the user to synchronize files in their computer.

Onedrive is a cloud storage system that is useful for the storage of files in a secured manner. A person can easily access their files whenever they want to.

In todays workplace a knowledge of onedrive has a great impact because

Onedrive offers an unlimited access to files whenever they are neededThe files can be available and accessed from anywhereIt helps with the organization of files in the work place.

One drive allows for this to be done even when offline. When online, there is an automatic synchronization of the made changes.

Read more at https://brainly.com/question/17163678?referrer=searchResults

Windows 10's one drive is useful because it enables users to synchronize information among various computers.Onedrive is indeed a cloud storage solution that can be used to store data in a secure environment.The user gets easy access to their files when their desire.In today's workplace, knowing how to use OneDrive is necessary because it gives unrestricted access to files anytime they're needed.The information can be transferred anywhere at.It assists with the arrangement of files in the workplace.It can be done and if you're not linked to the Network. Once you're online, the modifications you've performed are synchronized immediately.

Learn more:

brainly.com/question/24369537

Components of micro computer with diagram

Answers

Answer:

CPU, Program memory, Data memory, Output ports,  Input ports and Clock generator.

Explanation:

There are six basic components of a microcomputer which includes CPU, Program memory, Data memory, Output ports,  Input ports and Clock generator. CPU is the central processing unit which is considered as the brain of the computer. It is the part of a computer that executes instructions. Data memory is the place where data is stored that is present in the CPU.

g Add a throw statement to the processNumbers function that throws the message "An element in the list is not a number." if one of the elements in toProcess is not a number. Hint: The function isNaN() returns true if the parameter is not a number.

Answers

Answer and Explanation:

function processNumbers(alist){

var Ourarray= new array(alist);

Ourarray.foreach(

if(isNaN()){

Console.log( "An element in the list is not a number."};

break;

}

}

processNumbers(alist)

From the above, we have defined a function that takes an array parameter(the following array variable will make sure of that). We test each element in the array using foreach array function. The for each function runs the if statement and if isNan is true for each of the elements in the array.

Write a program named lastname_firstname_cities.py that works with information about large cities. Your program will open the cities.txt downloadfile. Each line in the file has the name of a city, its country, and its population. The first few lines of the file look like this:

Answers

Answer and Explanation:

Open your text editor and open new file. Save new file file as lastname_firstname_cities.py. The program will open the file cities.txt downloadfile hence :

dfile= open(cities.txt, "r")

If we write this into our lastname_firstname_cities.py file it will open our cities.txt downloadfile in read mode and text mode(by default unless we specify binary mode which is for images)

3. Coaxial/telephone cable sends
during the data transmission
signal

Answers

Answer:

high frequency signal.

A sinewave has a period (duration of one cycle) of 645 μs. What is the corresponding frequency of this sinewave, in kHz, expressed to 3 significant figures?


please help me figure this out I am so confused

Answers

The corresponding frequency of this sinewave, in kHz, expressed to 3 significant figures is: 155 kHz.

Given the following data:

Period = 645 μs

Note: μs represents microseconds.

Conversion:

1 μs = [tex]1[/tex] × [tex]10^{-6}[/tex] seconds

645 μs = [tex]645[/tex] × [tex]10^{-6}[/tex] seconds

To find corresponding frequency of this sinewave, in kHz;

Mathematically, the frequency of a waveform is calculated by using the formula;

[tex]Frequency = \frac{1}{Period}[/tex]

Substituting the value into the formula, we have;

[tex]Frequency = \frac{1}{645\; * \;10^{-6}}[/tex]

Frequency = 1550.39 Hz

Next, we would convert the value of frequency in hertz (Hz) to Kilohertz (kHz);

Conversion:

1 hertz = 0.001 kilohertz

1550.3876 hertz = X kilohertz

Cross-multiplying, we have;

X = [tex]0.001[/tex] × [tex]1550.39[/tex]

X = 155039 kHz

To 3 significant figures;

Frequency = 155 kHz

Find more information: https://brainly.com/question/23460034

Write a program that takes a date as input and outputs the date's season. The input is an integer to represent the month and an integer to represent the day. Ex: If the input is: 4 11 the output is: spring In addition, check if both integers are valid (an actual month and day). Ex: If the input is: 14 65 the output is: invalid The dates for each season are: spring: March 20 - June 20 summer: June 21 - September 21 autumn: September 22 - December 20 winter: December 21 - March 19

Answers

Answer:

Explanation:

The following program is written in Java. It is a function that takes in the two parameters, combines them as a String, turns the combined String back into an integer, and uses a series of IF statements to check the parameters and determine which season it belongs to. Then it prints the season to the screen. The code has been tested with the example provided in the question and the output can be seen in the attached image below.

class Brainly {

   public static void main(String[] args) {

       getSeason(4, 65);

       getSeason(4, 11);

   }

   public static void getSeason(int month, int day) {

       String combined = String.valueOf(month) + String.valueOf(day);

       int combinedInt = Integer.parseInt(combined);

       if ((month > 0 && month < 12) && (day > 0 && day < 31)) {

           if ((combinedInt >= 320) && (combinedInt <= 620)) {

               System.out.println("The Season is Spring");

           } else if ((combinedInt >= 621) && (combinedInt <= 921)) {

               System.out.println("The Season is Summer");

           } else if ((combinedInt >= 922) && (combinedInt <= 1220)) {

               System.out.println("The season is Autumn");

           } else {

               System.out.println("The Season is Winter");

           }

       } else {

           System.out.println("Invalid date");

       }

   }

}

, , and angle x and angle y are both in the first quadrant.

Answers

Answer:

[tex]\tan(x+y) = 3.73[/tex]

Explanation:

The missing part of the question are:

[tex]\sin(x) = \frac{1}{2}[/tex]

[tex]\cos(y) = \frac{\sqrt 2}{2}[/tex]

Required

[tex]\tan(x + y)[/tex]

First, we calculate [tex]\sin(y)[/tex] and [tex]\cos(x)[/tex]

We have:

[tex]\sin^2(x) + \cos^2(x) = 1[/tex]

So:

[tex](1/2)^2 + \cos^2(x) = 1[/tex]

Collect like terms

[tex]\cos^2(x) = 1 - (1/2)^2[/tex]

[tex]\cos^2(x) = 1 - \frac{1}{4}[/tex]

Take LCM

[tex]\cos^2(x) = \frac{4-1}{4}[/tex]

[tex]\cos^2(x) = \frac{3}{4}[/tex]

Square roots of both sides

[tex]\cos(x) = \frac{\sqrt 3}{2}[/tex]

Similarly,

[tex]\sin^2(y) + \cos^2(y) = 1[/tex]

So:

[tex]\sin^2(y)+(\sqrt 2/2)^2 = 1[/tex]

[tex]\sin^2(y)+ (2/4) = 1[/tex]

[tex]\sin^2(y)+1/2 = 1[/tex]

Collect like terms

[tex]\sin^2(y) = 1 - 1/2[/tex]

Take LCM

[tex]\sin^2(y) = \frac{2 -1}{2}[/tex]

[tex]\sin^2(y) = \frac{1}{2}[/tex]

Square roots of both sides

[tex]\sin(y) = \frac{1}{\sqrt2}[/tex]

Rationalize

[tex]\sin(y) = \frac{\sqrt2}{2}[/tex]

So, we have:

[tex]\sin(x) = \frac{1}{2}[/tex]           [tex]\cos(x) = \frac{\sqrt 3}{2}[/tex]

[tex]\cos(y) = \frac{\sqrt 2}{2}[/tex]        [tex]\sin(y) = \frac{\sqrt2}{2}[/tex]

[tex]\tan(x) = \sin(x) \div \cos(x)[/tex]

[tex]\tan(x) = \frac{1}{2} \div \frac{\sqrt 3}{2}[/tex]

Rewrite as:

[tex]\tan(x) = \frac{1}{2} * \frac{2}{\sqrt 3}[/tex]

[tex]\tan(x) = \frac{1}{\sqrt 3}[/tex]

Rationalize

[tex]\tan(x) = \frac{\sqrt 3}{3}[/tex]

Similarly

[tex]\tan(y) = \sin(y) \div \cos(y)[/tex]

[tex]\tan(y) = \frac{\sqrt 2}{2} \div \frac{\sqrt 2}{2}[/tex]

[tex]\tan(y) = 1[/tex]

Lastly,

[tex]\tan(x + y)= \frac{\tan(x) + \tan(y)}{1 - \tan(x) \cdot \tan(y)}[/tex]

[tex]\tan(x + y)= \frac{\frac{\sqrt3}{3} + 1}{1 - \frac{\sqrt3}{3} \cdot 1}[/tex]

[tex]\tan(x + y)= \frac{\frac{\sqrt3}{3} + 1}{1 - \frac{\sqrt3}{3}}[/tex]

Combine fractions

[tex]\tan(x + y)= \frac{\frac{\sqrt3+3}{3}}{\frac{3 - \sqrt3}{3}}[/tex]

Cancel out 3

[tex]\tan(x + y)= \frac{\sqrt3+3}{3 - \sqrt3}[/tex]

Using a calculator

[tex]\tan(x+y) = 3.73[/tex]

Other Questions
Henry wants to buy a new table saw for his carpentry shop. he saved $360 which is 2/3 of the price of the saw.how much does the table saw cost? In the short run, fixed costs: Group of answer choices are an important feature in a firm's decision to produce or not produce. have no impact on a firm's profit level. remain constant. do not exist. Whats another way to say:Walking out of my bedroom felt like a task. I cant believe I havent gotten out of my in a week nor talked to anyone.As soon as I reached my door, I rushed back to take my phone from my night stand.In a more grammatically correct way! Carnelian Company sells bicycles at $200 each. Variable cost per unit is $160, and total fixed cost is $120,600. Calculate the sales that Carnelian must make to earn an operating income of $21,500. a. $238,833.b. $716,500.c. $243,800.d. $626,000. F(x) = 6x+2, find f (x+3) why was jefferson chosen as the primary writer of the declaration of independence? Heidi comes from an upper-middle-class family, and after high school she went through a period of exploration. She spent some time traveling around Asia, worked at Disneyland for a few summers, and then waited tables in a ski town while learning to snowboard. Now she is attending college and has made a clear commitment to go into business. According to Marcia, Heidi's current identity status would be described as the phenomenon is called a revision why did it happen _________one moleculetwo moleculesone moletwo moles of H2(g) reacts with _________one moleculetwo moleculesone moletwo moles of F2(g) to form _________one moleculetwo moleculesone moletwo moles of HF(g). What are the solutions to the equation?x3 6x2 9x + 54 = 0 At a distance of 14,000 km from the center of Planet Z-99, the acceleration due to gravity is 32 m/s2. What is the acceleration due to gravity at a point 28,000 km from the center of this planet What is the difference between the temperature - 7 Celsius and - 12 Celsius on a scatter diagram If the integer $152AB1$ is a perfect square, what is the sum of the digits of its square root? What is the equation of the graph ? ILL pay 25 POINTS AND BRAINLIEST TO THE FIRST RIGHT ANSWER Write a speech, or a speech outline, that you would present to the Constitutional Convention of Oklahoma supporting the ideas of direct democracy. Suppose $1,000 was deposited into an account compounded quarterly that grew to $1,490 at rate of 6%. How long did it take for this to occur? Find side b, in triangle ABC. if angle B =42 degrees, a=6, c=4 assume that some huys are knis, all jiks are suds, and some aws are huys therefore it makes sense that (a) some knis may also be aws. (b) all huys are knis (c) all jiks are aws (d) some suds are knis. (e) all jiks are huys. What is the value of expression below when z=5? 5z4 The storys first sentence, a description of the family car shows the reader that a.the characters are not good with moneyb.the family in the story is very conscious of material statusc.Charles is ungrateful for the good things his parents have given himd.Charless parents have neglected routine repairs and maintenance