Language: C

#include <stdio.h>
int main()
{
  char day[3];
  scanf("%s",day);
  
  if(day=="SUN"){
    printf(7)
  }else if(day=="MON"){
    printf(6)
  }else if(day=="TUE"){
    printf(5)
  }else if(day=="WED"){
    printf(4)
  }else if(day=="THU"){
    printf(3)
  }else if(day=="FRI"){
    printf(2)
  }else if(day=="SAT"){
    printf(1)
  }else{
  }
}

Compiler output:
main.c: In function 'main':
main.c:8:12: error: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
    8 |     printf(7)
      |            ^
      |            |
      |            int
In file included from main.c:1:
/usr/include/stdio.h:363:43: note: expected 'const char * restrict' but argument is of type 'int'
  363 | extern int printf (const char *__restrict __format, ...);
      |                    ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
main.c:8:14: error: expected ';' before '}' token
    8 |     printf(7)
      |              ^
      |              ;
    9 |   }else if(day=="MON"){
      |   ~           
main.c:10:12: error: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
   10 |     printf(6)
      |            ^
      |            |
      |            int
/usr/include/stdio.h:363:43: note: expected 'const char * restrict' but argument is of type 'int'
  363 | extern int printf (const char *__restrict __format, ...);
      |                    ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
main.c:10:14: error: expected ';' before '}' token
   10 |     printf(6)
      |              ^
      |              ;
   11 |   }else if(day=="TUE"){
      |   ~           
main.c:12:12: error: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
   12 |     printf(5)
      |            ^
      |            |
      |            int
/usr/include/stdio.h:363:43: note: expected 'const char * restrict' but argument is of type 'int'
  363 | extern int printf (const char *__restrict __format, ...);
      |                    ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
main.c:12:14: error: expected ';' before '}' token
   12 |     printf(5)
      |              ^
      |              ;
   13 |   }else if(day=="WED"){
      |   ~           
main.c:14:12: error: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
   14 |     printf(4)
      |            ^
      |            |
      |            int
/usr/include/stdio.h:363:43: note: expected 'const char * restrict' but argument is of type 'int'
  363 | extern int printf (const char *__restrict __format, ...);
      |                    ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
main.c:14:14: error: expected ';' before '}' token
   14 |     printf(4)
      |              ^
      |              ;
   15 |   }else if(day=="THU"){
      |   ~           
main.c:16:12: error: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
   16 |     printf(3)
      |            ^
      |            |
      |            int
/usr/include/stdio.h:363:43: note: expected 'const char * restrict' but argument is of type 'int'
  363 | extern int printf (const char *__restrict __format, ...);
      |                    ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
main.c:16:14: error: expected ';' before '}' token
   16 |     printf(3)
      |              ^
      |              ;
   17 |   }else if(day=="FRI"){
      |   ~           
main.c:18:12: error: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
   18 |     printf(2)
      |            ^
      |            |
      |            int
/usr/include/stdio.h:363:43: note: expected 'const char * restrict' but argument is of type 'int'
  363 | extern int printf (const char *__restrict __format, ...);
      |                    ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
main.c:18:14: error: expected ';' before '}' token
   18 |     printf(2)
      |              ^
      |              ;
   19 |   }else if(day=="SAT"){
      |   ~           
main.c:20:12: error: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
   20 |     printf(1)
      |            ^
      |            |
      |            int
/usr/include/stdio.h:363:43: note: expected 'const char * restrict' but argument is of type 'int'
  363 | extern int printf (const char *__restrict __format, ...);
      |                    ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
main.c:20:14: error: expected ';' before '}' token
   20 |     printf(1)
      |              ^
      |              ;
   21 |   }else{
      |   ~