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C Programming Code Examples

C > Miscellaneous Code Examples

Tangent, calc. height of a tree

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/* Tangent, calc. height of a tree */ #include <stdio.h> #include <error.h> #include <stdlib.h> #include <math.h> /* 1 degrees = 0.0174532925 radians */ #define ONEDEGREE 0.0174532925 int main(int argc, char *argv[]) { double base = 0; double degrees = 0; double radians = 0; if(argc != 3) error(1, 0, "base degrees"); else { base = strtod(argv[1], (char **)NULL); degrees = strtod(argv[2], (char **)NULL); } /* convert degrees to radians */ radians = degrees * ONEDEGREE; printf("base : %.2f\n", base); printf("degrees : %.2f\n", degrees); printf("radians : %.2f\n", radians); printf("tan : %.2f\n", tan(radians)); printf("height : %.2f * %.2f = %.2f\n", base, tan(radians), (base * tan(radians))); return 0; }
main() Function in C
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. main() function is a user defined, body of the function is defined by the programmer or we can say main() is programmer/user implemented function, whose prototype is predefined in the compiler. Hence we can say that main() in c programming is user defined as well as predefined because it's prototype is predefined. main() is a system (compiler) declared function whose defined by the user, which is invoked automatically by the operating system when program is being executed. Its first function or entry point of the program from where program start executed, program's execution starts from the main. So main is an important function in c , c++ programming language.
Syntax for main() Function in C
void main() { ......... // codes start from here ......... }
void
is a keyword in C language, void means nothing, whenever we use void as a function return type then that function nothing return. here main() function no return any value. In place of void we can also use int return type of main() function, at that time main() return integer type value.
main
is a name of function which is predefined function in C library. • An operating system always calls the main() function when a programmers or users execute their programming code. • It is responsible for starting and ends of the program. • It is a universally accepted keyword in programming language and cannot change its meaning and name. • A main() function is a user-defined function in C that means we can pass parameters to the main() function according to the requirement of a program. • A main() function is used to invoke the programming code at the run time, not at the compile time of a program. • A main() function is followed by opening and closing parenthesis brackets.
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/* basic c program by main() function example */ #include <stdio.h> #include <conio.h> main() { printf (" It is a main() function "); int fun2(); // jump to void fun1() function printf ("\n Finally exit from the main() function. "); } void fun1() { printf (" It is a second function. "); printf (" Exit from the void fun1() function. "); } int fun2() { void fun1(); // jump to the int fun1() function printf (" It is a third function. "); printf (" Exit from the int fun2() function. "); return 0; }
#define Directive in C
In the C Programming Language, the #define directive allows the definition of macros within your source code. These macro definitions allow constant values to be declared for use throughout your code. Macro definitions are not variables and cannot be changed by your program code like variables. You generally use this syntax when creating constants that represent numbers, strings or expressions.
Syntax for #define Directive in C
#define NAME value /* this syntax creates a constant using define*/ // Or #define NAME (expression) /* this syntax creates a constant using define*/
NAME
is the name of a particular constant. It can either be defined in smaller case or upper case or both. Most of the developers prefer the constant names to be in the upper case to find the differences.
value
defines the value of the constant.
Expression
is the value that is assigned to that constant which is defined. The expression should always be enclosed within the brackets if it has any operators. In the C programming language, the preprocessor directive acts an important role within which the #define directive is present that is used to define the constant or the micro substitution. The #define directive can use any of the basic data types present in the C standard. The #define preprocessor directive lets a programmer or a developer define the macros within the source code. This macro definition will allow the constant value that should be declared for the usage. Macro definitions cannot be changed within the program's code as one does with other variables, as macros are not variables. The #define is usually used in syntax that created a constant that is used to represent numbers, strings, or other expressions. The #define directive should not be enclosed with the semicolon(;). It is a common mistake done, and one should always treat this directive as any other header file. Enclosing it with a semicolon will generate an error. The #define creates a macro, which is in association with an identifier or is parameterized identifier along with a token string. After the macro is defined, then the compiler can substitute the token string for each occurrence of the identifier within the source file.
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/* #define directive allows the definition of macros within your source code. These macro definitions allow constant values to be declared for use throughout your code. */ #include <stdio.h> #include <string.h> typedef struct Books { char title[50]; char author[50]; char subject[100]; int book_id; } Book; int main( ) { Book book; strcpy( book.title, "C Programming"); strcpy( book.author, "XCoder"); strcpy( book.subject, "C Programming Tutorial"); book.book_id = 6495407; printf( "Book title : %s\n", book.title); printf( "Book author : %s\n", book.author); printf( "Book subject : %s\n", book.subject); printf( "Book book_id : %d\n", book.book_id); return 0; }
Math tan() Function in C
Calculates the tangent of an angle. The tan() function calculates the tangent of the angle represented by its argument x as a number of radians. In the C Programming Language, the tan function returns the tangent of x. The C tan Function is a C Math Library Function. It is helpful to calculate the Trigonometry Tangent value for the specified expression.
Syntax for tan() Function in C
#include <math.h> double tan (double x);
x
Value representing an angle, expressed in radians. One radian is equivalent to 180/PI degrees. This function requires a number that represents an angle in radians as a parameter. The tan function returns tangent value of x, measured in radians. It is defined in math.h header file.
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/* return the tangent of an angle of x radians by tan() math function code example */ #include <stdio.h> #include <math.h> int main() { double x; double result; x = 2.3; result = tan(x); printf("tan(%.2lf) = %.2lf\n", x, result); x = -2.3; result = tan(x); printf("tan(%.2lf) = %.2lf\n", x, result); x = 0; result = tan(x); printf("tan(%.2lf) = %.2lf\n", x, result); return 0; }
printf() Function in C
Writes the C string pointed by format to the standard output (stdout). If format includes format specifiers (subsequences beginning with %), the additional arguments following format are formatted and inserted in the resulting string replacing their respective specifiers. printf format string refers to a control parameter used by a class of functions in the input/output libraries of C programming language. The string is written in a simple template language: characters are usually copied literally into the function's output, but format specifiers, which start with a % character, indicate the location and method to translate a piece of data (such as a number) to characters. "printf" is the name of one of the main C output functions, and stands for "print formatted". printf format strings are complementary to scanf format strings, which provide formatted input (parsing). In both cases these provide simple functionality and fixed format compared to more sophisticated and flexible template engines or parsers, but are sufficient for many purposes.
Syntax for printf() function in C
#include <stdio.h> int printf ( const char * format, ... );
format
C string that contains the text to be written to stdout. It can optionally contain embedded format specifiers that are replaced by the values specified in subsequent additional arguments and formatted as requested. A format specifier follows this prototype: [see compatibility note below] %[flags][width][.precision][length]specifier Where the specifier character at the end is the most significant component, since it defines the type and the interpretation of its corresponding argument:
specifier
a conversion format specifier.
d or i
Signed decimal integer
u
Unsigned decimal integer
o
Unsigned octal
x
Unsigned hexadecimal integer
X
Unsigned hexadecimal integer (uppercase)
f
Decimal floating point, lowercase
F
Decimal floating point, uppercase
e
Scientific notation (mantissa/exponent), lowercase
E
Scientific notation (mantissa/exponent), uppercase
g
Use the shortest representation: %e or %f
G
Use the shortest representation: %E or %F
a
Hexadecimal floating point, lowercase
A
Hexadecimal floating point, uppercase
c
Character
s
String of characters
p
Pointer address
n
Nothing printed. The corresponding argument must be a pointer to a signed int. The number of characters written so far is stored in the pointed location.
%
A % followed by another % character will write a single % to the stream. The format specifier can also contain sub-specifiers: flags, width, .precision and modifiers (in that order), which are optional and follow these specifications:
flags
one or more flags that modifies the conversion behavior (optional)
-
Left-justify within the given field width; Right justification is the default (see width sub-specifier).
+
Forces to preceed the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded with a - sign.
(space)
If no sign is going to be written, a blank space is inserted before the value.
#
Used with o, x or X specifiers the value is preceeded with 0, 0x or 0X respectively for values different than zero. Used with a, A, e, E, f, F, g or G it forces the written output to contain a decimal point even if no more digits follow. By default, if no digits follow, no decimal point is written.
0
Left-pads the number with zeroes (0) instead of spaces when padding is specified (see width sub-specifier).
width
an optional * or integer value used to specify minimum width field.
(number)
Minimum number of characters to be printed. If the value to be printed is shorter than this number, the result is padded with blank spaces. The value is not truncated even if the result is larger.
*
The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
.precision
an optional field consisting of a . followed by * or integer or nothing to specify the precision.
.number
For integer specifiers (d, i, o, u, x, X): precision specifies the minimum number of digits to be written. If the value to be written is shorter than this number, the result is padded with leading zeros. The value is not truncated even if the result is longer. A precision of 0 means that no character is written for the value 0. For a, A, e, E, f and F specifiers: this is the number of digits to be printed after the decimal point (by default, this is 6). For g and G specifiers: This is the maximum number of significant digits to be printed. For s: this is the maximum number of characters to be printed. By default all characters are printed until the ending null character is encountered. If the period is specified without an explicit value for precision, 0 is assumed.
.*
The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.
length
an optional length modifier that specifies the size of the argument.
... (additional arguments)
Depending on the format string, the function may expect a sequence of additional arguments, each containing a value to be used to replace a format specifier in the format string (or a pointer to a storage location, for n). There should be at least as many of these arguments as the number of values specified in the format specifiers. Additional arguments are ignored by the function. If a writing error occurs, the error indicator (ferror) is set and a negative number is returned. If a multibyte character encoding error occurs while writing wide characters, errno is set to EILSEQ and a negative number is returned.
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/* print formatted data to stdout by printf() function example */ #include <stdio.h> int main() { char ch; char str[100]; int a; float b; printf("Enter any character \n"); scanf("%c", &ch); printf("Entered character is %c \n", ch); printf("Enter any string ( upto 100 character ) \n"); scanf("%s", &str); printf("Entered string is %s \n", str); printf("Enter integer and then a float: "); // Taking multiple inputs scanf("%d%f", &a, &b); printf("You entered %d and %f", a, b); return 0; }
#include Directive in C
#include is a way of including a standard or user-defined file in the program and is mostly written at the beginning of any C/C++ program. This directive is read by the preprocessor and orders it to insert the content of a user-defined or system header file into the following program. These files are mainly imported from an outside source into the current program. The process of importing such files that might be system-defined or user-defined is known as File Inclusion. This type of preprocessor directive tells the compiler to include a file in the source code program. Here are the two types of file that can be included using #include: • Header File or Standard files: This is a file which contains C/C++ function declarations and macro definitions to be shared between several source files. Functions like the printf(), scanf(), cout, cin and various other input-output or other standard functions are contained within different header files. So to utilise those functions, the users need to import a few header files which define the required functions. • User-defined files: These files resembles the header files, except for the fact that they are written and defined by the user itself. This saves the user from writing a particular function multiple times. Once a user-defined file is written, it can be imported anywhere in the program using the #include preprocessor.
Syntax for #include Directive in C
#include "user-defined_file"
Including using " ": When using the double quotes(" "), the preprocessor access the current directory in which the source "header_file" is located. This type is mainly used to access any header files of the user's program or user-defined files.
#include <header_file>
Including using <>: While importing file using angular brackets(<>), the the preprocessor uses a predetermined directory path to access the file. It is mainly used to access system header files located in the standard system directories.
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/* #include directive tells the preprocessor to insert the contents of another file into the source code at the point where the #include directive is found. */ // C program to illustrate file inclusion // <> used to import system header file #include <stdio.h> // " " used to import user-defined file #include "process.h" // main function int main() { // add function defined in process.h add(10, 20); // mult function defined in process.h multiply(10, 20); // printf defined in stdio.h printf("Process completed"); return 0; }
strtod() Function in C
Convert string to double. Parses the C-string str interpreting its content as a floating point number (according to the current locale) and returns its value as a double. If endptr is not a null pointer, the function also sets the value of endptr to point to the first character after the number. The function first discards as many whitespace characters (as in isspace) as necessary until the first non-whitespace character is found. Then, starting from this character, takes as many characters as possible that are valid following a syntax resembling that of floating point literals (see below), and interprets them as a numerical value. A pointer to the rest of the string after the last valid character is stored in the object pointed by endptr.
Syntax for strtod() Function in C
#include<stdlib.h> double strtod (const char* str, char** endptr);
str
C-string beginning with the representation of a floating-point number.
endptr
Reference to an already allocated object of type char*, whose value is set by the function to the next character in str after the numerical value. This parameter can also be a null pointer, in which case it is not used. The strtod function converts a string to a double. The strtod function skips all white-space characters at the beginning of the string, converts the subsequent characters as part of the number, and then stops when it encounters the first character that isn't a number. On success, the function returns the converted floating point number as a value of type double. If no valid conversion could be performed, the function returns zero (0.0). If the correct value is out of the range of representable values for the type, a positive or negative HUGE_VAL is returned, and errno is set to ERANGE. If the correct value would cause underflow, the function returns a value whose magnitude is no greater than the smallest normalized positive number (some library implementations may also set errno to ERANGE in this case). A valid floating point number for strtod using the "C" locale is formed by an optional sign character (+ or -), followed by one of: - A sequence of digits, optionally containing a decimal-point character (.), optionally followed by an exponent part (an e or E character followed by an optional sign and a sequence of digits). - A 0x or 0X prefix, then a sequence of hexadecimal digits (as in isxdigit) optionally containing a period which separates the whole and fractional number parts. Optionally followed by a power of 2 exponent (a p or P character followed by an optional sign and a sequence of hexadecimal digits). - INF or INFINITY (ignoring case). - NAN or NANsequence (ignoring case), where sequence is a sequence of characters, where each character is either an alphanumeric character (as in isalnum) or the underscore character (_). If the first sequence of non-whitespace characters in str does not form a valid floating-point number as just described, or if no such sequence exists because either str is empty or contains only whitespace characters, no conversion is performed and the function returns a zero value.
Data races
The array pointed by str is accessed, and the pointer pointed by endptr is modified (if not null).
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/* convert string to double by strtod() function code example */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <errno.h> int main(int argc, const char * argv[]) { /* Define temporary variables */ char value[10]; char *eptr; double result; /* Copy a value into the variable */ /* It's okay to have whitespace before the number */ strcpy(value, " 958"); /* Convert the provided value to a double */ result = strtod(value, &eptr); /* If the result is 0, test for an error */ if (result == 0) { /* If the value provided was out of range, display a warning message */ if (errno == ERANGE) printf("The value provided was out of range\n"); } /* Display the converted result */ printf("%f decimal\n", result); /* Copy a hexadecimal value into the variable */ strcpy(value, "0x8b2"); /* Convert the hexadecimal provided value to a double */ result = strtod(value, &eptr); /* If the result is 0, test for an error */ if (result == 0) { /* If the value provided was out of range, display a warning message */ if (errno == ERANGE) printf("The value provided was out of range\n"); } /* Display the converted result */ printf("%f decimal\n", result); return 0; }
If Else Statement in C
The if-else statement is used to perform two operations for a single condition. The if-else statement is an extension to the if statement using which, we can perform two different operations, i.e., one is for the correctness of that condition, and the other is for the incorrectness of the condition. Here, we must notice that if and else block cannot be executed simiulteneously. Using if-else statement is always preferable since it always invokes an otherwise case with every if condition.
Syntax for if-else Statement in C
if (test expression) { // run code if test expression is true } else { // run code if test expression is false }
If the test expression is evaluated to true, • statements inside the body of if are executed. • statements inside the body of else are skipped from execution. If the test expression is evaluated to false, • statements inside the body of else are executed • statements inside the body of if are skipped from execution.
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/* if else statement in C language */ // Check whether an integer is odd or even #include <stdio.h> int main() { int number; printf("Enter an integer: "); scanf("%d", &number); // True if the remainder is 0 if (number%2 == 0) { printf("%d is an even integer.",number); } else { printf("%d is an odd integer.",number); } return 0; }


In C, A "Pointer" holds the Address of another variable of same type. When a Pointer Holds the address of another pointer then such type of pointer is known as "pointer-to-pointer" or
In C program, we are going to accept a string. Program will check for word inside string and if word founds then program will reverse that word. Similarly it'll Reverse out all the Words.
Fibonacci series is a series of numbers where the current number is the sum of previous 2 terms. For Example: 0, 1, 1, 2, 3, 5, 8, 13, 21,... Here c is the current term, b is the n-1th term
C Language program print all even numbers from 1 to n using for loop. So first let us talk about the easiest way to print even numbers. If I ask you to list all even numbers from 1 to