Transcript E3-PPT

Assignment Operators
=
+= -=
*=
/=
%=
Statement
Equivalent Statement
a=a+2;
a += 2 ;
a=a-3;
a -= 3 ;
a=a*2;
a *= 2 ;
a=a/4;
a /= 4 ;
a=a%2;
a %= 2 ;
b=b+(c+2);
b += c + 2 ;
d=d*(e-5);
d *= e - 5 ;
int number = 10, sum = 0;
What
is
the
output?
int i;
printf("enter int: ");
scanf("%d", &i);
switch (i)
{
case 1: printf("Exam2 =>Nov18\n");
printf("1:sum =%d number=%d\n", sum, number);
break;
case 2: number +=3;
printf("2:sum =%d number=%d\n", sum, number);
case 3: sum = number++;
printf("3:sum =%d number=%d\n", sum, number);
case 4: sum = --number;
printf("4:sum =%d number=%d\n", sum, number);
case 5: printf("fuzzball\n");
break;
default: sum = number;
printf("D:sum =%d number=%d\n", sum, number);
}
printf("Final: sum =%d number=%d\n", sum, number);
Problems with Reading Characters
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When getting characters, whether using scanf( ) or
getchar( ), realize that you are reading only one
character.
What will the user actually type? The character he/she
wants to enter, followed by pressing ENTER.
So, the user is actually entering two characters, his/her
response and the newline character.
Unless you handle this, the newline character will remain
in the stdin stream causing problems the next time you
want to read a character. Another call to scanf() or
getchar( ) will remove it.
Reading Chars
#include <stdio.h>
int main ( )
{
char myChar, newline ;
printf (“Enter a character: “) ;
myChar = getchar( ) ;
newline = getchar( ) ; /* could also usescanf(“%c”, &newline) ; */
printf (“The value of |%c| is |%c|.\n”, myChar, newline ) ;
return 0 ;
}
User’s input is
a
Lets use this as an Enter symbol
What happens when user hits Enter key on the keyboard?  \n
Reading Chars
#include <stdio.h>
int main ( )
{
char myChar='o', newline ;
printf(“Enter e to exit\n") ;
while(myChar!=‘e')
{
printf("Enter a character:") ;
myChar = getchar( );
newline = getchar( );
printf ("The value of |%c| is |%c|.\n", myChar, newline ) ;
}
printf(“See You Later!") ;
return 0;
}
Additional Concerns with Garbage in
stdin
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When we were reading integers using scanf( ), we didn’t
seem to have problems with the newline character, even
though the user was typing ENTER after the integer.
That is because scanf( ) was looking for the next integer
and ignored the newline (whitespace).
If we use scanf (“%d”, &num); to get an integer, the
newline is still stuck in the input stream.
If the next item we want to get is a character, whether we
use scanf( ) or getchar( ), we will get the newline.
We have to take this into account and remove it.
switch in a event controlled loop
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Create a menu that continually prompts the user to enter 'H' to print a
greeting in English, ‘A’ to print a greeting in Hawaiin, 'N' to print a greeting in
Hindi, and S to print a greeting in Hebrew. The menu should also include an
option 'E' which exits the program. Menu should look something like this:
Please enter:
H -> To print greeting in English
A -> To print greeting in Hawaiian
N -> To print greeting in Hindi
S -> To print greeting in Hebrew
E -> To exit
'H', it prints "Hello";
'A' it prints "Aloha";
'N' it prints "Namasthe";
‘S’ it prints "Shalom".
'E', the program should print "Adios" before it exits the program.
getchar( ) Example Using EOF
#include <stdio.h>
int main ()
{
int grade, aCount, bCount, cCount, dCount, fCount ;
aCount = bCount = cCount = dCount = fCount = 0 ;
while ( (grade = getchar( ) ) != EOF ) {
switch ( grade ) {
case ‘A’: aCount++; break ;
case ‘B’: bCount++; break ;
case ‘C’ : cCount++; break ;
case ‘D’: dCount++; break ;
case ‘F’: fCount++; break ;
default : break ;
}
}
return 0 ;
}