Reference: Molay, Understanding Unix/Linux Programming, Chapter 7.1-7.6

Space

Video game: control video display to draw images at specific locations on the screen.

OS: kernel loads programs into memory space and keeps track of the location of each program.

Time

Video game: images move of the screen at different speeds; events occur with different intervals.

OS: kernel schedules programs to run for short intervals; schedules internal tasks to be done at different times.

Interruptions

Video game: users can send input to the game whenever they like.

OS: kernel must respond quickly to the input sent at unpredictable times by users and other external devices.

Multitasking

Video game: must keep multiple objects moving and respond to input at the same time.

OS: kernel must be able to run multiple processes and respond to input at the same time.

Allows the programmer to set set the position of the cursor and control the appearance of text on a terminal screen. The screen is treated as a 2D array. Each location is identified by the (row, column) pair of values with (0,0) at the upper left corner of the screen. Uses a virtual screen where all changes are made. Function refresh() is used to apply these changes to the actual screen.

Basic curses functions:

initscr()

Initializes the curses library and the tty

endwin()

Turns off curses library and the tty

refresh()

Updates the screen

move(r,c)

Moves the cursor to the position (r,c)

addstr(s)

Draws string s on the screen in the current position

addch(c)

Draws char c on the screen in the current position

clear()

Clears the screen

Function sleep(unsigned int s) suspend thread execution for an interval of s seconds.

#include <stdio.h>
#include <curses.h>

main() {
   int i;
   initscr();
   clear();
   for(i=0; i<LINES; i++ ){
      move( i, i+i );
      addstr("Hello, world");
      refresh();
      sleep(1);
      move(i,i+i);               /* move back    */
      addstr("             ");   /* erase line   */
   }
   endwin();
}

sleep(n) works as follows:

signal(SIGALRM, handler);   /* install a handler for alarm */
alarm(n);                   /* set the alarm               */
pause();                    /* suspend the execution       */

int getitimer(int which, struct itimerval *val);
int setitimer(int which, const struct itimerval *newval, struct itimerval *oldval);

• which is either ITIMER_REAL, ITIMER_VIRTUAL, or ITIMER_PROF
• val pointer to current settings
• newval pointer to settings to be installed
• oldval pointer to settings being replaced
• returns -1 on error, 0 on success

Use the set_ticker() function described on p. 213 to set an interval timer.