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C Programming
Questions related to the C Computer Programming Language. This ranges all the way from K&R to the most recent ANSI incarnations. C has become one of the most popular languages today, and has been used to write all sorts of things for nearly all of the modern operating systems and applications. It it a good compromise between speed, power, and complexity.
9,649 Questions
How is the top-down approach to information security superior to the bottom-up approach?
The project is initiated by upper-level managers who issue policy, procedures and processes, dictate the goals and expect outcomes, and determine accountability for each required action.
the only reason that you study languages is so that when you have a job and your custemer is french you would be able to understand them or even you go to France or any country you would understand themand interact.
No. ROM means read-only memory so, by definition, you can't write to it.
What value of c makes 9x2 plus 24x plus c a perfect square?
16? using 16, you have (3x2 + 4)(3x2 + 4) = 9x2 + 24x + 16
How do you write a program in c plus plus to check if an array is symmetric?
To determine if an array is symmetric, the array must be square. If so, check each element against its transpose. If all elements are equal, the array is symmetric.
For a two-dimensional array (a matrix) of order n, the following code will determine if it is symmetric or not:
template
bool symmetric(const std::array
{
for (size_t r=0 ; r
return true! // symmetric!
}
In C program, premitive is a kind of data type which is predefined in C programming language.
What is a complex data structure?
A complex data structure is the kind of structure that has two arrays. One array hols the real part of the complex data and the other array holds the imaginary part.
What control statement exhibits a looping structure?
It depends on the programming language, however most high-level languages will provide some variant of the standard 'for' loop in addition to some variant of the 'while' and 'do-while' loop.
Difference between enum and const in c?
members in union and enum both shares memory and the size of the union is the size of the highest element like if there is one int and one char in union then the size of union will be the size of an int. if an int and an float are there then the size of the union will be the size of the float. This is not the case in the enum. it has similar type of members. and the value of the members can be assign manually like this
enum e{ZERO,ONE,TWO=20,THREE};
here ZERO will have value 0, ONE will have value 1, TWO will be having 20 , THREE will be having 21.. and so on
Answer: they are no way similar, no point in comparing them.
No, it is one dimensional. In only has one measurement, length.
Which algorithm is more efficient- insertion sort algorithm or merge sort algorithm?
On average merge sort is more efficient however insertion sort could potentially be faster. As a result it depends how close to reverse order the data is. If it is likely to be mostly sorted, insertion sort is faster, if not, merge sort is faster.
What are the components of C language application?
You use the #include directive to instruct the compiler to add a specific include file to your program during compilation. The #include directive in this sample program means "Add the contents of the file STDIO.H." Most C programs require one or more include files. More information about include files is presented on Day 21, "Advanced Compiler Use."
The Variable Definition (Line 4)A variable is a name assigned to a data storage location. Your program uses variables to store various kinds of data during program execution. In C, a variable must be defined before it can be used. A variable definition informs the compiler of the variable's name and the type of data it is to hold. In the sample program, the definition on line 4, int a,b,c;, defines three variables--named a, b, and c--that will each hold an integer value. More information about variables and variable definitions is presented on Day 3, "Storing Data: Variables and Constants." The Function Prototype (Line 6)A function prototype provides the C compiler with the name and arguments of the functions contained in the program. It must appear before the function is used. A function prototype is distinct from a function definition, which contains the actual statements that make up the function. (Function definitions are discussed in more detail later in this chapter.) Program Statements (Lines 11, 12, 15, 16, 19, 20, 22, and 28)The real work of a C program is done by its statements. C statements display information on-screen, read keyboard input, perform mathematical operations, call functions, read disk files, and carry out all the other operations that a program needs to perform. Most of this book is devoted to teaching you the various C statements. For now, remember that in your source code, C statements are generally written one per line and always end with a semicolon. The statements in MULTIPLY.C are explained briefly in the following sections. printf()The printf() statement (lines 11, 15, and 20) is a library function that displays information on-screen. The printf() statement can display a simple text message (as in lines 11 and 15) or a message and the value of one or more program variables (as in line 20).
scanf()The scanf() statement (lines 12 and 16) is another library function. It reads data from the keyboard and assigns that data to one or more program variables.
The program statement on line 19 calls the function named product(). In other words, it executes the program statements contained in the function product(). It also sends the arguments a and b to the function. After the statements in product() are completed, product() returns a value to the program. This value is stored in the variable named c.
returnLines 22 and 28 contain return statements. The return statement on line 28 is part of the function product(). It calculates the product of the variables x and y and returns the result to the program statement that called product(). The return statement on line 22 returns a value of 0 to the operating system just before the program ends.
The Function Definition (Lines 26 Through 29)A function is an independent, self-contained section of code that is written to perform a certain task. Every function has a name, and the code in each function is executed by including that function's name in a program statement. This is known as calling the function.The function named product(), in lines 26 through 29, is a user-defined function. As the name implies, user-defined functions are written by the programmer during program development. This function is simple. All it does is multiply two values and return the answer to the program that called it. On Day 5, "Functions: The Basics," you will learn that the proper use of functions is an important part of good C programming practice.
Note that in a real C program, you probably wouldn't use a function for a task as simple as multiplying two numbers. I've done this here for demonstration purposes only.
C also includes library functions that are a part of the C compiler package. Library functions perform most of the common tasks (such as screen, keyboard, and disk input/output) your program needs. In the sample program, printf() and scanf() are library functions.
Program Comments (Lines 1, 10, 14, 18, and 25)Any part of your program that starts with /* and ends with */ is called a comment. The compiler ignores all comments, so they have absolutely no effect on how a program works. You can put anything you want into a comment, and it won't modify the way your program operates. A comment can span part of a line, an entire line, or multiple lines. Here are three examples: /* A single-line comment */ int a,b,c; /* A partial-line comment */ /* a comment spanning multiple lines */However, you shouldn't use nested comments (in other words, you shouldn't put one comment within another). Most compilers would not accept the following: /* /* Nested comment */ */
Some compilers do allow nested comments. Although this feature might be tempting to use, you should avoid doing so. Because one of the benefits of C is portability, using a feature such as nested comments might limit the portability of your code. Nested comments also might lead to hard-to-find problems.
Many beginning programmers view program comments as unnecessary and a waste of time. This is a mistake! The operation of your program might be quite clear while you're writing it--particularly when you're writing simple programs. However, as your programs become larger and more complex, or when you need to modify a program you wrote six months ago, you'll find comments invaluable. Now is the time to develop the habit of using comments liberally to document all your programming structures and operations.NOTE: Many people have started using a newer style of comments in their C programs. Within C++ and Java, you can use double forward slashes to signal a comment. Here are two examples: // This entire line is a comment int x; // Comment starts with slashes.
The two forward slashes signal that the rest of the line is a comment. Although many C compilers support this form of comment, you should avoid it if you're interested in portability.DOadd abundant comments to your program's source code, especially near statements or functions that could be unclear to you or to someone who might have to modify it later.
DON'T add unnecessary comments to statements that are already clear. For example, entering /* The following prints Hello World! on the screen */ printf("Hello World!");
might be going a little too far, at least once you're completely comfortable with the printf() function and how it works.
DO learn to develop a style that will be helpful. A style that's too lean or cryptic doesn't help, nor does one that's so verbose that you're spending more time commenting than programming!
Braces (Lines 9, 23, 27, and 29)You use braces ({}) to enclose the program lines that make up every C function--including the main() function. A group of one or more statements enclosed within braces is called a block. As you will see in later chapters, C has many uses for blocks. Running the ProgramTake the time to enter, compile, and run MULTIPLY.C. It provides additional practice in using your editor and compiler. Recall these steps from Day 1, "Getting Started with C":1. Make your programming directory current.2. Start your editor.3.Enter the source code for MULTIPLY.C exactly as shown in Listing 2.1, but be sure to omit the line numbers and colons.4. Save the program file.5. Compile and link the program by entering the appropriate command(s) for your compiler. If no error messages are displayed, you can run the program by entering multiply at the command prompt.6. If one or more error messages are displayed, return to step 2 and correct the errors. A Note on AccuracyA computer is fast and accurate, but it also is completely literal. It doesn't know enough to correct your simplest mistake; it takes everything you enter exactly as you entered it, not as you meant it!This goes for your C source code as well. A simple typographical error in your program can cause the C compiler to choke, gag, and collapse. Fortunately, although the compiler isn't smart enough to correct your errors (and you'll make errors--everyone does!), it is smart enough to recognize them as errors and report them to you. (You saw in the preceding chapter how the compiler reports error messages and how you interpret them.)
A Review of the Parts of a ProgramNow that all the parts of a program have been described, you should be able to look at any program and find some similarities. Look at Listing 2.2 and see whether you can identify the different parts. Listing 2.2. LIST_IT.C.1: /* LIST_IT.C--This program displays a listing with line numbers! */ 2: #includeANALYSIS: LIST_IT.C is similar to PRINT_IT.C, which you entered in exercise 7 of Day 1. Listing 2.2 displays saved C program listings on-screen instead of printing them on the printer.
Looking at this listing, you can summarize where the different parts are. The required main() function is in lines 8 through 32. Lines 2 and 3 have #include directives. Lines 6, 10, and 11 have variable definitions. A function prototype, void display_usage(void), is in line 5. This program has many statements (lines 13, 15, 16, 19, 21, 22, 25, 27, 28, 30, 31, 36, and 37). A function definition for display_usage() fills lines 34 through 38. Braces enclose blocks throughout the program. Finally, only line 1 has a comment. In most programs, you should probably include more than one comment line.
LIST_IT.C calls many functions. It calls only one user-defined function, display_usage(). The library functions that it uses are exit() in lines 16 and 22; fopen() in line 19; fprintf() in lines 21, 28, 36, and 37; fgets() in line 27; and fclose() in line 30. These library functions are covered in more detail throughout this book.
SummaryThis chapter was short, but it's important, because it introduced you to the major components of a C program. You learned that the single required part of every C program is the main() function. You also learned that the program's real work is done by program statements that instruct the computer to perform your desired actions. This chapter also introduced you to variables and variable definitions, and it showed you how to use comments in your source code.In addition to the main() function, a C program can use two types of subsidiary functions: library functions, supplied as part of the compiler package, and user-defined functions, created by the programmer.
Q&AQ What effect do comments have on a program?AComments are for the programmer. When the compiler converts the source code to object code, it throws the comments and the white space away. This means that they have no effect on the executable program. Comments do make your source file bigger, but this is usually of little concern. To summarize, you should use comments and white space to make your source code as easy to understand and main-tain as possible.Q What is the difference between a statement and a block?A A block is a group of statements enclosed in braces ({}). A block can be used in most places that a statement can be used.Q How can I find out what library functions are available?A Many compilers come with a manual dedicated specifically to documenting the library functions. They are usually in alphabetical order. Another way to find out what library functions are available is to buy a book that lists them. Appendix E, "Common C Functions," lists many of the available functions. After you begin to understand more of C, it would be a good idea to read these appendixes so that you don't rewrite a library function. (There's no use reinventing the wheel!) WorkshopThe Workshop provides quiz questions to help you solidify your understanding of the material covered and exercises to provide you with experience in using what you've learned. Quiz1. What is the term for a group of one or more C statements enclosed in braces?2. What is the one component that must be present in every C program?3. How do you add program comments, and why are they used?4. What is a function?5. C offers two types of functions. What are they, and how are they different?6. What is the #include directive used for?7. Can comments be nested?8. Can comments be longer than one line?9. What is another name for an include file?10. What is an include file? Exercises1. Write the smallest program possible.2. Consider the following program: 1: /* EX2-2.C */ 2: #includeThe advantage is that while accessing a block that is stored
at the middle of a file, its location can be determined by chasing the
pointers stored in the FAT as opposed to accessing all of the individual
blocks of the file in a sequential manner to find the pointer to the target
block. Typically, most of the FAT can be cached in memory and therefore
the pointers can be determined with just memory accesses instead of
having to access the disk blocks.
What are the different cryptography algorithms?
There are many different algorithms used in cryptography - RSA, DES and Rabine ciphers are a few that can be used - as well as others that are used to help determine the constants in a system like Euclid's algorithm.
Difference between deterministic and nondeterministic loop?
Deterministic and non-deterministic loops
A deterministic loop is predictable. The number of iterations of such a loop are known in advance, even before the loop has started. Most counting loops are deterministic. Before they start, we can say how many times they will execute.
A non-deterministic loop is not easily predicted. A loop that is driven by the response of a user is not deterministic, because we cannot predict the response of the user. Non-deterministic loops usually are controlled by a boolean and the number of iterations is not known in advance.
C. 6
The full form of this is:
char* argv[];
Where argv is a pointer to a null-terminated array of null-terminated strings.
We use this type of argument to pass command line switches to the main function:
int main (char * argv[], int argc);
The names of these arguments, argv and argc, are conventional. The argc argument tells us how many elements are in the argv argument, such that argv[0] is the full-qualified name of the executable and argv[argc] is the null-terminator of the array. Any and all other elements (argv[n], such that 0<n<argc) represent programmer-defined command-line switches.
What is the Fibonacci code used for?
In mathematics, Fibonacci coding is a universal code which encodes positive integers into binary code words
What ORGANIC compound has C-C-C-O-C-C-C-C?
Please rephrase your question with more detail.
Making a LOT of assumptions, the answer MIGHT be propoxybutane.
How will floating point value 5.375 be saved in memory that is its bit representation in memory?
5.37510 is 101.0112 Normalize and you get 1.01011E210 (1.010112 * 22) IEEE 754 single precision format is 1 Sign Bit, 8 Exponent Bits in excess 127 format, and 23 mantissa bits with leading implied one missing, so... Sign bit is 0 (+) Exponent is 10000001 (127 + 2) Mantissa is 0101100 00000000 00000000 (101011... with leading 1 omitted) Splice this together and you get 01000000 10101100 00000000 00000000 But in Little Endian machines, like Intel IA 32, you reverse the bytes, so you get 00000000 00000000 10101100 010000000 All of this said, however, you should not care what the bit representation is in memory, because that makes you platform dependent, i.e. non-portable.
Explain sequence point concept in C?
A sequence point is a point where all processing, including side-effects, has been completed before proceeding. It is important because if you have two expressions with side effects you do not necessarily know which one gets executed first unless you use an implicit or explicit sequence point.
Why you require different operating system for different compiler?
Actually it's the other way around. You require different compilers for different operating systems. The reason for this is that an operating system is basically an intermediate step for a person to be able to interact with the hardware on their system. Each OS has a different way to do this, and so compilers must be different for each one, even for the same language.
Example of a letter with enumeration?
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