#include <stdio.h>

#define STR_MAX 	20
#define Y_OFFSET	5
#define X_OFFSET	25
#define TASK(x) 	printf( RC ); \
			printf("item No. %d is selected", x); \
			fflush( stdout ); \
			sleep(1) 
#define CLEAR 		printf( CLS ); printf( MOVE, 1, 1 )

/****************************************************************************/
/*                        VT100 escape sequence                             */
/****************************************************************************/

#define CLS	"\e[2J"
#define MOVE	"\e[%d;%dH"
#define BOLD	"\e[1m"
#define RESET	"\e[0m"
#define SC	"\e7"	/* store cursor */
#define RC	"\e8"	/* restore cursor */
#define D_RIGHT	"\e[0K" /* delete right side of the cursor */

/****************************************************************************/
/*                        menu table                                        */
/****************************************************************************/	

struct menu{
	int	y, x;
	char	*item;
};

struct menu menu_table[] = {
	{0, 5,	"Main Menu"		},
	{3, 0,	"1 Computer (press 1)"	},
	{5, 0,	"2 Logic    (press 2)"	},
	{7, 0,	"3 Others   (press 3)"	},
	{9, 0,	"4 Exit     (press 4)"	},
	{11, 5,	"key in please : "	},
	{0, 0,	NULL			},
};

/****************************************************************************/
/*                        display menu                                      */
/****************************************************************************/

display_menu( table )
	struct menu *table;
{
	int i, n;
	int select;

	printf( CLS );
	for (; table->item; table++) {
		printf( MOVE, Y_OFFSET + table->y, X_OFFSET + table->x );
		printf( "%s", table->item );
	}
}

/****************************************************************************/
/*                                keyin                                     */
/****************************************************************************/

int keyin(start, end)
	int start, end;
{
	char key_in[STR_MAX];
	int select;

	printf( SC );
	while(1) {
		fgets( key_in, STR_MAX, stdin );
		if (isdigit( key_in[0] )) {
			sscanf( key_in, "%d", &select);
			if (select >= start && select <= end)
				return select;
		}
		printf( RC );
		printf( D_RIGHT );
	}
}

/****************************************************************************/
/*                            main()                                        */
/****************************************************************************/

main()
{
	int item_number;

	while(1) {
		display_menu( menu_table );
		item_number = keyin( 1, 4 );
	
		switch ( item_number ) {
		case 1:
			TASK(1);
			break;
		case 2:
			TASK(2);
			break;
		case 3:
			TASK(3);
			break;
		case 4:
			CLEAR;
			exit(0);
		}
	}
}