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C-SPAN.org gives you access to C-SPAN's daily coverage of Washington and more than 200,000 hours of extensively indexed and archived C-SPAN video. Random encryption of string in C#. Rate this: Please Sign up or sign in to vote. A random encryption key: string encryptKey = Path.GetRandomFileName.Replace('.' How do I generate random characters within a string using C? Random string in c. We would like to show you a description here but the site won’t allow us. Dec 18, 2016  The well-known System.Random class lets us generate random numbers quickly. However, the values provided by System.Random are not truly random. Instead, they are pseudo-random. The return values should only be used in case true randomness is not that important, such as in the classic number-guessing game. In case you need a random value to be.

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A function is a group of statements that together perform a task. Every C program has at least one function, which is main(), and all the most trivial programs can define additional functions.

You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division is such that each function performs a specific task.

A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.

The C standard library provides numerous built-in functions that your program can call. For example, strcat() to concatenate two strings, memcpy() to copy one memory location to another location, and many more functions.

A function can also be referred as a method or a sub-routine or a procedure, etc.

Defining a Function

The general form of a function definition in C programming language is as follows −

A function definition in C programming consists of a function header and a function body. Here are all the parts of a function −

• Return Type − A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return_type is the keyword void.

• Function Name − This is the actual name of the function. The function name and the parameter list together constitute the function signature.

• Parameters − A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.

• Function Body − The function body contains a collection of statements that define what the function does.

Example

Given below is the source code for a function called max(). This function takes two parameters num1 and num2 and returns the maximum value between the two −

Function Declarations

A function declaration tells the compiler about a function name and how to call the function. The actual body of the function can be defined separately.

C-span

A function declaration has the following parts −

For the above defined function max(), the function declaration is as follows −

Parameter names are not important in function declaration only their type is required, so the following is also a valid declaration −

Function declaration is required when you define a function in one source file and you call that function in another file. In such case, you should declare the function at the top of the file calling the function.

Calling a Function

While creating a C function, you give a definition of what the function has to do. To use a function, you will have to call that function to perform the defined task.

When a program calls a function, the program control is transferred to the called function. A called function performs a defined task and when its return statement is executed or when its function-ending closing brace is reached, it returns the program control back to the main program.

To call a function, you simply need to pass the required parameters along with the function name, and if the function returns a value, then you can store the returned value. For example − Generate ssh key in linux.

We have kept max() along with main() and compiled the source code. While running the final executable, it would produce the following result −

Function Arguments

If a function is to use arguments, it must declare variables that accept the values of the arguments. These variables are called the formal parameters of the function.

Formal parameters behave like other local variables inside the function and are created upon entry into the function and destroyed upon exit.

While calling a function, there are two ways in which arguments can be passed to a function −

By default, C uses call by value to pass arguments. In general, it means the code within a function cannot alter the arguments used to call the function.

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Arrays allow to define type of variables that can hold several data items of the same kind. Similarly structure is another user defined data type available in C that allows to combine data items of different kinds.

Structures are used to represent a record. Suppose you want to keep track of your books in a library. You might want to track the following attributes about each book −

• Title
• Author
• Subject
• Book ID

C# Generate Random Guid

Defining a Structure

To define a structure, you must use the struct statement. The struct statement defines a new data type, with more than one member. The format of the struct statement is as follows −

The structure tag is optional and each member definition is a normal variable definition, such as int i; or float f; or any other valid variable definition. At the end of the structure's definition, before the final semicolon, you can specify one or more structure variables but it is optional. Here is the way you would declare the Book structure −

Accessing Structure Members

To access any member of a structure, we use the member access operator (.). The member access operator is coded as a period between the structure variable name and the structure member that we wish to access. You would use the keyword struct to define variables of structure type. The following example shows how to use a structure in a program −

When the above code is compiled and executed, it produces the following result −

Structures as Function Arguments

You can pass a structure as a function argument in the same way as you pass any other variable or pointer.

When the above code is compiled and executed, it produces the following result −

Pointers to Structures

You can define pointers to structures in the same way as you define pointer to any other variable −

Now, you can store the address of a structure variable in the above defined pointer variable. To find the address of a structure variable, place the '&'; operator before the structure's name as follows −

To access the members of a structure using a pointer to that structure, you must use the → operator as follows −

Let us re-write the above example using structure pointer.

When the above code is compiled and executed, it produces the following result −

Bit Fields

Bit Fields allow the packing of data in a structure. This is especially useful when memory or data storage is at a premium. Typical examples include −

• Packing several objects into a machine word. e.g. 1 bit flags can be compacted.

• Reading external file formats -- non-standard file formats could be read in, e.g., 9-bit integers.

C allows us to do this in a structure definition by putting :bit length after the variable. For example −

Here, the packed_struct contains 6 members: Four 1 bit flags f1.f3, a 4-bit type and a 9-bit my_int.

C automatically packs the above bit fields as compactly as possible, provided that the maximum length of the field is less than or equal to the integer word length of the computer. If this is not the case, then some compilers may allow memory overlap for the fields while others would store the next field in the next word.