/* 
 * time.h
 * This file has no copyright assigned and is placed in the Public Domain.
 * This file is a part of the mingw-runtime package.
 * No warranty is given; refer to the file DISCLAIMER within the package.
 *
 * Date and time functions and types.
 *
 */

#ifndef	_TIME_H_
#define	_TIME_H_

/* All the headers include this file. */
#include <_mingw.h>

#define __need_wchar_t
#define __need_size_t
#define __need_NULL
#ifndef RC_INVOKED
#include <stddef.h>
#endif	/* Not RC_INVOKED */

/*
 * Number of clock ticks per second. A clock tick is the unit by which
 * processor time is measured and is returned by 'clock'.
 */
#define	CLOCKS_PER_SEC	((clock_t)1000)
#define	CLK_TCK		CLOCKS_PER_SEC


#ifndef RC_INVOKED

/*
 * A type for storing the current time and date. This is the number of
 * seconds since midnight Jan 1, 1970.
 * NOTE: This is also defined in non-ISO sys/types.h.
 */
#ifndef _TIME_T_DEFINED
typedef	long	time_t;
#define _TIME_T_DEFINED
#endif

#ifndef __STRICT_ANSI__
/* A 64-bit time_t to get to Y3K */
#ifndef _TIME64_T_DEFINED
typedef __int64 __time64_t;
#define _TIME64_T_DEFINED
#endif
#endif
/*
 * A type for measuring processor time (in clock ticks).
 */
#ifndef _CLOCK_T_DEFINED
typedef	long	clock_t;
#define _CLOCK_T_DEFINED
#endif

#ifndef _TM_DEFINED
/*
 * A structure for storing all kinds of useful information about the
 * current (or another) time.
 */
struct tm
{
	int	tm_sec;		/* Seconds: 0-59 (K&R says 0-61?) */
	int	tm_min;		/* Minutes: 0-59 */
	int	tm_hour;	/* Hours since midnight: 0-23 */
	int	tm_mday;	/* Day of the month: 1-31 */
	int	tm_mon;		/* Months *since* january: 0-11 */
	int	tm_year;	/* Years since 1900 */
	int	tm_wday;	/* Days since Sunday (0-6) */
	int	tm_yday;	/* Days since Jan. 1: 0-365 */
	int	tm_isdst;	/* +1 Daylight Savings Time, 0 No DST,
				 * -1 don't know */
};
#define _TM_DEFINED
#endif

#ifdef	__cplusplus
extern "C" {
#endif

_CRTIMP clock_t __cdecl	clock (void);
_CRTIMP time_t __cdecl	time (time_t*);
_CRTIMP double __cdecl	difftime (time_t, time_t);
_CRTIMP time_t __cdecl	mktime (struct tm*);

/*
 * These functions write to and return pointers to static buffers that may
 * be overwritten by other function calls. Yikes!
 *
 * NOTE: localtime, and perhaps the others of the four functions grouped
 * below may return NULL if their argument is not 'acceptable'. Also note
 * that calling asctime with a NULL pointer will produce an Invalid Page
 * Fault and ***** out your program. Guess how I know. Hint: stat called on
 * a directory gives 'invalid' times in st_atime etc...
 */
_CRTIMP char* __cdecl		asctime (const struct tm*);
_CRTIMP char* __cdecl		ctime (const time_t*);
_CRTIMP struct tm*  __cdecl	gmtime (const time_t*);
_CRTIMP struct tm*  __cdecl	localtime (const time_t*);

_CRTIMP size_t __cdecl		strftime (char*, size_t, const char*, const struct tm*);

#ifndef __STRICT_ANSI__

extern _CRTIMP void __cdecl	_tzset (void);

#ifndef _NO_OLDNAMES
extern _CRTIMP void __cdecl	tzset (void);
#endif

_CRTIMP char* __cdecl	_strdate(char*);
_CRTIMP char* __cdecl	_strtime(char*);

/* These require newer versions of msvcrt.dll (6.10 or higher). */ 
#if __MSVCRT_VERSION__ >= 0x0601
_CRTIMP __time64_t __cdecl  _time64( __time64_t*);
_CRTIMP __time64_t __cdecl  _mktime64 (struct tm*);
_CRTIMP char* __cdecl _ctime64 (const __time64_t*);
_CRTIMP struct tm*  __cdecl _gmtime64 (const __time64_t*);
_CRTIMP struct tm*  __cdecl _localtime64 (const __time64_t*);
#endif /* __MSVCRT_VERSION__ >= 0x0601 */

/*
 * _daylight: non zero if daylight savings time is used.
 * _timezone: difference in seconds between GMT and local time.
 * _tzname: standard/daylight savings time zone names (an array with two
 *          elements).
 */
#ifdef __MSVCRT__

/* These are for compatibility with pre-VC 5.0 suppied MSVCRT. */
extern _CRTIMP int* __cdecl	__p__daylight (void);
extern _CRTIMP long* __cdecl	__p__timezone (void);
extern _CRTIMP char** __cdecl	__p__tzname (void);

__MINGW_IMPORT int	_daylight;
__MINGW_IMPORT long	_timezone;
__MINGW_IMPORT char 	*_tzname[2];

#else /* not __MSVCRT (ie. crtdll) */

#ifndef __DECLSPEC_SUPPORTED

extern int*	_imp___daylight_dll;
extern long*	_imp___timezone_dll;
extern char**	_imp___tzname;

#define _daylight	(*_imp___daylight_dll)
#define _timezone	(*_imp___timezone_dll)
#define _tzname		(*_imp___tzname)

#else /* __DECLSPEC_SUPPORTED */

__MINGW_IMPORT int	_daylight_dll;
__MINGW_IMPORT long	_timezone_dll;
__MINGW_IMPORT char*	_tzname[2];

#define _daylight	_daylight_dll
#define _timezone	_timezone_dll

#endif /* __DECLSPEC_SUPPORTED */

#endif /* not __MSVCRT__ */

#ifndef _NO_OLDNAMES

#ifdef __MSVCRT__

/* These go in the oldnames import library for MSVCRT. */
__MINGW_IMPORT int	daylight;
__MINGW_IMPORT long	timezone;
__MINGW_IMPORT char 	*tzname[2];

#else /* not __MSVCRT__ */

/* CRTDLL is royally messed up when it comes to these macros.
   TODO: import and alias these via oldnames import library instead 
   of macros.  */

#define daylight        _daylight
/* NOTE: timezone not defined because it would conflict with sys/timeb.h.
   Also, tzname used to a be macro, but now it's in moldname. */
__MINGW_IMPORT char 	*tzname[2];

#endif /* not __MSVCRT__ */

#endif	/* Not _NO_OLDNAMES */
#endif	/* Not __STRICT_ANSI__ */

#ifndef _WTIME_DEFINED
/* wide function prototypes, also declared in wchar.h */
#ifndef __STRICT_ANSI__
#ifdef __MSVCRT__
_CRTIMP wchar_t* __cdecl	_wasctime(const struct tm*);
_CRTIMP wchar_t* __cdecl	_wctime(const time_t*);
_CRTIMP wchar_t* __cdecl	_wstrdate(wchar_t*);
_CRTIMP wchar_t* __cdecl	_wstrtime(wchar_t*);
#if __MSVCRT_VERSION__ >= 0x0601
_CRTIMP wchar_t* __cdecl	_wctime64 (const __time64_t*);
#endif
#endif /*  __MSVCRT__ */
#endif /* __STRICT_ANSI__ */
_CRTIMP size_t __cdecl		wcsftime (wchar_t*, size_t, const wchar_t*, const struct tm*);
#define _WTIME_DEFINED
#endif /* _WTIME_DEFINED */ 

#ifdef	__cplusplus
}
#endif

#endif	/* Not RC_INVOKED */

#endif	/* Not _TIME_H_ */ 

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    return 0;
    
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About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
} 

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
} 

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}  

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition); 

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}