/* example from http://barnyard.syr.edu/quickies/led.c */ /* led.c: print out number as if on 7 line led display. I.e., write integer   given on command line like this:        _   _       _     |  _|  _| |_| |_     | |_   _|   |  _| etc.    We assume the terminal behaves like a classical teletype. So the top   lines of all digits have to be printed first, then the middle lines of   all digits, etc.    By Terry R. McConnell compile: cc -o led led.c If you just want to link in the subroutine print_led that does all thework, compile with -DNO_MAIN, and declare the following in any source filethat uses the call: extern void print_led(unsigned long x, char *buf); Bug: you cannot call repeatedly to print more than one number to a line.That would require curses or some other terminal API that allows moving thecursor to a previous line. */   #include <stdlib.h>#include <stdio.h> #define MAX_DIGITS 32#define NO_MAIN  /* Print the top line of the digit d into buffer.    Does not null terminate buffer. */ void topline(int d, char *p){    *p++ = ' ';   switch(d){       /* all these have _ on top line */       case 0:      case 2:      case 3:      case 5:      case 7:      case 8:      case 9:         *p++ = '_';         break;      default:         *p++=' ';    }   *p++=' ';} /* Print the middle line of the digit d into the buffer.    Does not null terminate. */ void midline(int d, char *p){    switch(d){       /* those that have leading | on middle line */       case 0:      case 4:      case 5:      case 6:      case 8:      case 9:         *p++='|';         break;      default:         *p++=' ';	   }   switch(d){       /* those that have _ on middle line */       case 2:      case 3:      case 4:      case 5:      case 6:      case 8:      case 9:         *p++='_';         break;      default:         *p++=' ';    }   switch(d){       /* those that have closing | on middle line */       case 0:      case 1:      case 2:      case 3:      case 4:      case 7:      case 8:      case 9:         *p++='|';         break;      default:         *p++=' ';    }} /* Print the bottom line of the digit d. Does not null terminate. */ void botline(int d, char *p){     switch(d){       /* those that have leading | on bottom line */       case 0:      case 2:      case 6:      case 8:         *p++='|';         break;      default:         *p++=' ';	   }   switch(d){       /* those that have _ on bottom line */       case 0:      case 2:      case 3:      case 5:      case 6:      case 8:         *p++='_';         break;      default:         *p++=' ';    }   switch(d){       /* those that have closing | on bottom line */       case 0:      case 1:      case 3:      case 4:      case 5:      case 6:      case 7:      case 8:      case 9:         *p++='|';         break;      default:         *p++=' ';    }} /* Write the led representation of integer to string buffer. */ void print_led(unsigned long x, char *buf){    int i=0,n;   static int d[MAX_DIGITS];     /* extract digits from x */    n = ( x == 0L ? 1 : 0 );  /* 0 is a digit, hence a special case */    while(x){      d[n++] = (int)(x%10L);      if(n >= MAX_DIGITS)break;      x = x/10L;   }    /* print top lines of all digits */    for(i=n-1;i>=0;i--){      topline(d[i],buf);      buf += 3;      *buf++=' ';   }   *buf++='\n'; /* move teletype to next line */    /* print middle lines of all digits */    for(i=n-1;i>=0;i--){      midline(d[i],buf);      buf += 3;      *buf++=' ';   }   *buf++='\n';    /* print bottom lines of all digits */    for(i=n-1;i>=0;i--){      botline(d[i],buf);      buf += 3;      *buf++=' ';   }   *buf++='\n';   *buf='\0';} int main(){   char buf[5*MAX_DIGITS];   print_led(1234567, buf);   printf("%s\n",buf);    return 0;} #ifndef NO_MAINint main(int argc, char **argv){    int i=0,n;   long x;   static int d[MAX_DIGITS];   char buf[5*MAX_DIGITS];    if(argc != 2){      fprintf(stderr,"led: usage: led integer\n");      return 1;   }    /* fetch argument from command line */    x = atol(argv[1]);    /* sanity check */    if(x<0){      fprintf(stderr,"led: %d must be non-negative\n",x);      return 1;   }    print_led(x,buf);   printf("%s\n",buf);    return 0; }#endif /* vim: set expandtab ts=4 sw=3 sts=3 tw=80 :*/