im reading a character given by the user through the keyboard .

now ,what is correct :

if ($gramma == s) then

OR

if ($gramma == 's') then

where s is supposed to be the character given by the user .

if its not any of that whats the correct one ?

thanks in advance

Don't use csh for scripting.
If you're using sh or bash, syntax is available in man test .
PS: There is no difference between a char and a string in shell. So forget the single quote for single char. It's always double quote.