• Using C# Variable In Javascript
• Using Directive
• New Windows 10 Updates Are Force Installing Microsoft Edge

See full list on programiz.com. Mar 06, 2020 The using statement in C# is exited when the end of the 'using' statement block or the execution exits the 'using' statement block indirectly, for example - an exception is thrown. The 'using' statement allows you to specify multiple resources in a single statement. The object could also be created outside the 'using' statement.

1. Speech Recognition using C#. This article provides information about how to implement Speech Recognition capabilities in C# and Speech SDK 5.1. This article provides some elementary information about how to implement Speech Recognition capabilities into your applications. The tools we would use to speech enable would be the speech SDK 5.1.
2. Note: Replace the C: RepairSource Windows placeholder with the location of your repair source. For more information about using the DISM tool to repair Windows, reference Repair a Windows Image. At the command prompt, type the following command, and then press ENTER.

As always, a function is a module of code that takes information in (referring to that information with local symbolic names called parameters), does some computation, and (usually) returns a new piece of information based on the parameter information.

Basic Function Design Pattern

For the basic syntax of a function in C, please refer to the C Function Design Pattern chapter.

Dot C files

The 'recipe' for a function (the function's code) is always stored in a '.C' file. In C there can be many functions written in a single file.

Ordering of functions in a file

The order of functions inside a file is arbitrary. It does not matter if you put function one at the top of the file and function two at the bottom, or vice versa.

Caveat: In order for one function to 'see' (use) another function, the 'prototype' of the function must be seen in the file before the usage. If a function uses another function that is textually written above it in the file, then this will automatically be true. If the function uses a function that is 'below it' in a file, then the prototype should occur at the top of the file... see prototypes below.

A Function Prototype

In C, all functions must be written to return a specific TYPE of information and to take in specific types of data (parameters). This information is communicated to the compiler via a function prototype.

Here is the syntax for the function declaration or Prototype:

A Prototype can occur at the top of a C source code file to describe what the function returns and what it takes (return type and parameter list). When this is the case (occuring at the top of the file), the function prototype should be followed by a semi-colon

The function prototype is also used at the beginning of the code for the function. Thus the prototype can occur twice in a C source code file. When the prototype occurs with the code NO semicolon is used.

The Main Function

In C, the 'main' function is treated the same as every function, it has a return type (and in some cases accepts inputs via parameters). The only difference is that the main function is 'called' by the operating system when the user runs the program. Thus the main function is always the first code executed when a program starts.

Examples of C Functions:

Return Type of a C function

Every C function must specify the type of data that is being generated. For example, the max function above returns a value of type 'double'. Inside the function, the line 'return X;' must be found, where X is a value or variable containing a value of the given type.

The return statement

When a line of code in a function that says: 'return X;' is executed, the function 'ends' and no more code in the function is executed. The value of X (or the value in the variable represented by X) becomes the result of the function.

Calling a C function (aka invoke a function)

When one piece of code invokes or calls a function, it is done by the following syntax:

The function name must match exactly the name of the function in the function prototype. The args are a list of values (or variables containing values) that are 'passed' into the function.

The number of args 'passed' into a function must exactly match the number of parameters required for the function. The type of each arg must exactly match the type of each parameter. The return variable type must exactly match the return type of the function.

The 'variable' in the example above must have a type equivalent to the return type of the function. Inside the function, somewhere will be the line 'return X'. The value of X is then copied into the 'variable'.

Parameters in C functions

A Parameter is the symbolic name for 'data' that goes into a function. There are two ways to pass parameters in C: Pass by Value, Pass by Reference.

• Pass by Value

  Pass by Value, means that a copy of the data is made and stored by way of the name of the parameter. Any changes to the parameter have NO affect on data in the calling function.

• Pass by Reference

  A reference parameter 'refers' to the original data in the calling function. Thus any changes made to the parameter are ALSO MADE TO THE ORIGINAL variable.

  There are two ways to make a pass by reference parameter:

  1. ARRAYS

     Arrays are always pass by reference in C. Any change made to the parameter containing the array will change the value of the original array.

  2. The ampersand used in the function prototype.

     function ( & parameter_name )

     To make a normal parameter into a pass by reference parameter, we use the '& param' notation. The ampersand (&) is the syntax to tell C that any changes made to the parameter also modify the original variable containing the data.

Pass by Value Example:

In C, the default is to pass by value. For example:

Pass by Reference Example:

Warning: C++

I suggest that you use a C++ compiler such as g++ which allows the following pass by reference syntax (a much more modern style). The Syntax is to use the '&' in front of the parameter name in the function declaration. The calling code and usage inside the function are the same as before. For example:

Warning: Standard C - Using 'Pointers'

With standard C you have to put the & in the calling location as opposed to next to the parameter in the function declaration; further, you must use a '*' in the parameter list, and use a '*' whenever using the parameter inside the function.

The '*' is used to define a 'pointer', a discussion of which is beyond the scope of this simple example. Feel free to Google 'Pointers in C' for a long treatise on how to use them... or take my advice, and (as a beginning programmer) avoid them.

In summary, if you use a reference parameter, any changes to the parameter inside the function are reflected 'outside' of the function (i.e., in the calling function)! If you don't use the & (pass by reference), then we get the same behavior as in Matlab (i.e., the value is changed inside the called function, but maintains its original value in the calling function.

One reason to use reference parameters is to make the program more 'efficient'. Consider passing in a structure as a parameter. If the structure is very big, and we copy all of it, then we are using a lot of unnecessary memory.

Array Parameter Example (ALWAYS pass by reference)

Arrays are always passed by reference in C. They do not use the '&' notation, but are pass by reference none the less. For example:

Constant Reference

To protect from accidentally changing a reference parameter, when we really want it not to be changed (we just want to save time/memory) we can use the C keyword const. For example:

Void Functions

If a function does not return a value, then a special 'TYPE' is used to tell the computer this. The return type is 'void' (all lower case).

Void functions are mostly used in two classes of functions.

Using C# Variable In Javascript

1. The first is a function that prints information for the user to read. For example (for our purposes), the printf function is treated as a void function. (In actuality, printf returns an integer which is the number of characters printed... but we almost always ignore this value.)

2. The second use of void functions is with 'reference' parameters (e.g., Arrays). A reference parameter is not a copy of the input data, as is so often the case. A reference parameter is an 'alias' for the same bucket in memory as the input data. Thus any change made to a reference parameter is in fact made to the original variable!

There are reasons to prefer developing Bluetooth applicationsin C instead of in a high level language such as Python. The Pythonenvironment might not be available or might not fit on the target device;strict application requirements on program size, speed, and memory usage maypreclude the use of an interpreted language like Python; the programmer maydesire finer control over the local Bluetooth adapter than PyBluez provides;or the project may be to create a shared library for other applications tolink against instead of a standalone application.As of this writing, BlueZ is a powerful Bluetooth communications stack withextensive APIs that allows a user to fully exploit all local Bluetoothresources, but it has no official documentation. Furthermore, there is verylittle unofficial documentation as well. Novice developers requestingdocumentation on the official mailing lists [1] are typicallyrebuffed and told to figure out the API by reading through the BlueZ sourcecode. This is a time consuming process that can only reveal small pieces ofinformation at a time, and is quite often enough of an obstacle to deter manypotential developers.

This chapter presents a short introduction to developing Bluetoothapplications in C with BlueZ. The tasks covered in chapter 2 are nowexplained in greater detail here for C programmers.

A simple program that detects nearby Bluetooth devices is shown in Example 4-1. The program reserves system Bluetoothresources, scans for nearby Bluetooth devices, and then looks up the userfriendly name for each detected device. A more detailed explanation of thedata structures and functions used follows.

Example 4-1. simplescan.c

4.1.1. Compilation

To compile our program, invoke gcc and link againstlibbluetooth

# gcc -o simplescan simplescan.c -lbluetooth

4.1.2. Explanation

Using Directive

The basic data structure used to specify a Bluetooth device address is thebdaddr_t. All Bluetooth addresses in BlueZ will be storedand manipulated as bdaddr_t structures. BlueZ provides twoconvenience functions to convert between strings andbdaddr_t structures.

str2ba takes an string of the form ``XX:XX:XX:XX:XX:XX',where each XX is a hexadecimal number specifying an octet of the 48-bitaddress, and packs it into a 6-byte bdaddr_t.ba2str does exactly the opposite.

Local Bluetooth adapters are assigned identifying numbers starting with 0, anda program must specify which adapter to use when allocating system resources.Usually, there is only one adapter or it doesn't matter which one is used, sopassing NULL to hci_get_route willretrieve the resource number of the first available Bluetooth adapter.

It is not a good idea to hard-code the devicenumber 0, because that is not always the id of the first adapter. For example,if there were two adapters on the system and the first adapter (id 0) isdisabled, then the first available adapter is the one withid 1.

If there are multiple Bluetooth adapters present, then to choose the adapterwith address ``01:23:45:67:89:AB', pass the char * representation of the address to hci_devid and use that inplace of hci_get_route.

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Most Bluetooth operations require the use of an open socket.hci_open_dev is a convenience function that opens aBluetooth socket with the specified resource number [2]. To be clear, the socket openedby hci_open_dev represents a connection to themicrocontroller on the specified local Bluetooth adapter, and not a connectionto a remote Bluetooth device. Performing low level Bluetooth operationsinvolves sending commands directly to the microcontroller with this socket, andSection 4.5 discusses this in greater detail.

After choosing the local Bluetooth adapter to use and allocating systemresources, the program is ready to scan for nearby Bluetooth devices. In theexample, hci_inquiry performs a Bluetooth device discoveryand returns a list of detected devices and some basic information about them inthe variable ii. On error, it returns -1 and setserrno accordingly.

hci_inquiry is one of the few functions that requires theuse of a resource number instead of an open socket, so we use thedev_id returned by hci_get_route. Theinquiry lasts for at most 1.28 * len seconds, and at mostmax_rsp devices will be returned in the output parameterii, which must be large enough to accommodatemax_rsp results. We suggest using amax_rsp of 255 for a standard 10.24 second inquiry.

If flags is set to IREQ_CACHE_FLUSH, thenthe cache of previously detected devices is flushed before performing thecurrent inquiry. Otherwise, if flags is set to 0, then theresults of previous inquiries may be returned, even if the devices aren't inrange anymore.

The inquiry_info structure is defined as

For the most part, only the first entry - the bdaddr field,which gives the address of the detected device - is of any use. Occasionally,there may be a use for the dev_class field, which givesinformation about the type of device detected (i.e. if it's a printer, phone,desktop computer, etc.) and is described in the Bluetooth AssignedNumbers [3]. The rest of the fields are used for lowlevel communication, and are not useful for most purposes. The interestedreader can see the Bluetooth Core Specification [4] for more details.

Once a list of nearby Bluetooth devices and their addresses has been found,the program determines the user-friendly names associated with thoseaddresses and presents them to the user. Thehci_read_remote_name function is used for this purpose.

hci_read_remote_name tries for at mosttimeout milliseconds to use the socketsock to query the user-friendly name of the device withBluetooth address ba. On success,hci_read_remote_name returns 0 and copies at most the firstlen bytes of the device's user-friendly name intoname. On failure, it returns -1 and setserrno accordingly.

Notes[1]

http://www.bluez.org/lists.html

[2]

for thecurious, it makes a call to socket(AF_BLUETOOTH, SOCK_RAW,BTPROTO_HCI), followed by a call to bind with thespecified resource number.

[3]

https://www.bluetooth.org/foundry/assignnumb/document/baseband

[4]

http://www.bluetooth.org/spec