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Conditional Directives in C

By Dinesh Thakur

The conditional directives are meant to control the compilation process. By using them we may conditionally include certain statements of the program for compilation. If the condition is not met the statements are not included. These directives also help us not to include duplicate files in the program and cause error. For example, see the following code: [Read more…] about Conditional Directives in C

Function strftime () in C

By Dinesh Thakur

The syntax of the function is as follows:

size_t strftime(char* s, size_t maxsize, const char* format, const struct tm * Tmptr);

The function strftime () formats the broken-down time tm into an array pointed to by s according to the specified formatting string pointed to by format. The size of array is limited by maxsize. The formatting string consists of 0 or more conversion Specifiers and ordinary characters. The ordinary characters placed in the formatting string are copied into s without any conversion. Each specifier consists of a percent character(%) followed by a character that determines the action of conversion specifier. Some conversion Specifiers may have an additional modifier character E or 0 placed between% symbol and the conversion specifier character. The strftime() function returns the number of characters placed in the arrays, not including the terminating Null character.

Illustrates application of function strftime (). [Read more…] about Function strftime () in C

Function localtime () in C

By Dinesh Thakur

The function localtime () converts the calendar time, i.e., the output of function time (), into a broken-down time expressed as local time, and returns the pointer to broken-down time. If the conversion into local time fails, the function returns NULL pointer. The prototype of the function is written in the following manner: [Read more…] about Function localtime () in C

Function difftime () in C

By Dinesh Thakur

The function difftime ()returns the difference between two calendar times in seconds, i.e., number of seconds elapsed between two calendar times time2 and time]. The calendar time represents the time elapsed since 00:00:00 hours 01 January 1970, GMT. The function returns the difference in seconds as a double number. The function prototype is written as follows: [Read more…] about Function difftime () in C

Function time () in C

By Dinesh Thakur

The function time () returns the current calendar time, i.e., the number of seconds elapsed since 00:00:00 hour January 1, 1970 GMT (or gmt are used alternatively) up to the execution of the function. The function prototype is written as follows: [Read more…] about Function time () in C

void Pointers in C

By Dinesh Thakur

The assignment operator (=) may be used on pointers of the same type. However, if the types of pointers (types of variables to which they point) are not same then we will have to do type casting of one of these to the type of the other to use assignment operator. However, the void pointer (void * ) can represent any pointer type. Thus, any type of pointer may be assigned to a void pointer. However, the reverse is not valid. A void pointer cannot be assigned to any other type of pointer without first converting the void pointer to that type. [Read more…] about void Pointers in C

Vectors with Structures in C

By Dinesh Thakur

Since structures are multivalue, multitype data objects, they can be considered to form a useful tool in manipulation of quantities such as vectors, complex variables, etc. For this we define functions of the type struct, i.e., the return value of the function is a structure. The function may have arguments of type struct besides other arguments. Let us define a structure with three components of vector as its data members as shown below. [Read more…] about Vectors with Structures in C