#include <stdio.h>

void main( int argc, /* Number of strings in array argv */
char *argv[], /* Array of command-line argument strings */
char **envp ) /* Array of environment variable strings */
{
int count;

/* Display each command-line argument. */
printf( "\nCommand-line arguments:\n" );
for( count = 0; count < argc; count++ )
printf( " argv[%d] %s\n", count, argv[count] );

/* Display each environment variable. */
printf( "\nEnvironment variables:\n" );
while( *envp != NULL )
printf( " %s\n", *(envp++) );
return;
}

One example of output from this program is:
Command-line arguments:
argv[0] C:\MSC\TEST.EXE

Environment variables:
COMSPEC=C:\NT\SYSTEM32\CMD.EXE

PATH=c:\nt;c:\binb;c:\binr;c:\nt\system32;c:\word;c:\help;c:\msc;c:\;
PROMPT=[$p]
TEMP=c:\tmp
TMP=c:\tmp
EDITORS=c:\binr
WINDIR=c:\nt

#include <stdio.h>
#include <stdlib.h>
void main( void )
{
printf("The full path of the executing program is : %Fs\n", _pgmptr);
}

#include <stdio.h>
#include <stdlib.h>

void main( void )
{
FILE *stream;
if( (stream = fopen( "NOSUCHF.ILE", "r" )) == NULL )
{
perror( "Couldn't open file" );
abort();
}
else
fclose( stream );
}

Output
Couldn't open file: No such file or directory
abnormal program termination

class ShowData
{
public:
// Constructor opens a file.
ShowData( const char *szDev )
{
OutputDev = fopen( szDev, "w" );
}
// Destructor closes the file.
~ShowData() { fclose( OutputDev ); }
// Disp function shows a string on the output device.
void Disp( char *szData )
{
fputs( szData, OutputDev );
}
private:
FILE *OutputDev;
};

// Define a static object of type ShowData. The output device
// selected is "CON" -- the standard output device.
ShowData sd1 = "CON";
// Define another static object of type ShowData. The output
// is directed to a file called "HELLO.DAT"
ShowData sd2 = "hello.dat";

int main()
{
sd1.Disp( "hello to default device\n" );
sd2.Disp( "hello to file hello.dat\n" );
return 0;
}
In the preceding example, the static objects sd1 and sd2 are created and initialized before entry to main.
After this program terminates using the return statement, first sd2 is destroyed and then sd1. The destructor for the ShowData class closes the files associated with these static objects. (For more information about initialization, constructors, and destructors, see Chapter 11, Special Member Functions.)

Another way to write this code is to declare the ShowData objects with block scope, allowing them to be destroyed when they go out of scope:
int main()
{
ShowData sd1, sd2( "hello.dat" );
sd1.Disp( "hello to default device\n" );
sd2.Disp( "hello to file hello.dat\n" );
return 0;
}

#include <stdlib.h>
#include <stdio.h>

void fn1( void ), fn2( void ), fn3( void ), fn4( void );

void main( void )
{
atexit( fn1 );
atexit( fn2 );
atexit( fn3 );
atexit( fn4 );
printf( "This is executed first.\n" );
}

void fn1()
{ printf( "next.\n" ); }

void fn2()
{ printf( "executed " ); }

void fn3()
{ printf( "is " ); }

void fn4()
{ printf( "This " ); }

Output
This is executed first.
This is executed next.