Lesson 15 - Learning Goals

DO LOOP - test at end

      Do the loop once ( execute loop statements ).

      Then, is logical expression true ?

      If YES, go through the loop statements again.

      If NO, exit the loop.

/* How many digits ? */

   ndigit = 0;
   number = 10000 ;
   do 
   {
      number = number / 10 ;
      ndigit = ndigit + 1 ;
   } while ( number != 0 ) ;

SCANF

#include <stdio.h>
main( )
{
   int d1, d2, d3, d4, d5, d6, d7 ;

   while ( scanf("%1d%1d%1d%1d%1d%1d%1d",
   &d1, &d2, &d3, &d4, &d5, &d6, &d7) = = 7 ) 
   {
      printf (" Reverse : %1d%1d%1d%1d%1d%1d%1d \n",
      d7, d6, d5, d4, d3, d2, d1 ) ;
   }

}

EXAMPLE :

***************************************************

Input                                 Output

1234567           Reverse : 7654321 

7 6 5 4 3 2 1     Reverse : 1234567

0987654 2345678   Reverse : 4567890
                  
                  Reverse : 8765432

1234567890        Reverse : 7654321

1234              Reverse : 4321098

SCANF

#include <stdio.h>

main( )
{

char cmd [ 15 ] ;
int i ;
i = scanf (" %s ", cmd ) ; /* No & before cmd because cmd 
is an array */

if ( i = = -1 ) printf (" Blank input \n ") ;
else printf ("The input is %s \n ", cmd) ;
}

Input : 23456

Output : Blank input

scanf returns a function value equal to the number of good arguments.

It returns 0 if there is no input, and -1 if EOF (end of file)

FOR LOOP - general loop form

      for ( Initialize ; logical expression ; update variable )

      Is logical expression true ?

      If YES, go through the loop statements.

      Then, Update the initial condition

      Is logical expression true ?

      If YES, go through the loop statements.

      Then, Update the initial condition

      Is logical expression true ?

      .

      .

      .

      If NO, exit the loop.

EXAMPLE :

/* Execute the same statement 10 times */

for( i=0 ; i < 10 ; i++ )
{
   j = j + 1 ;
} 

FOR LOOP IN C

for ( init, init, . . . , init ;
   expression ;
   update, update, . . . , update )
{
   statements ;
}

EXAMPLE :

for ( ndigit = 1; number >= 10 ; ndigit += 1 ) 
{
   number = number/10 ;
}

DIFFERENCES FROM FORTRAN :

• No trip count calculated ahead of time
• Update not restricted to increments
• No special '' loop counter ''