int main(){
   char uname, passwd;

   printf("Enter your username: ");
   scanf("%c", uname);
   printf("Enter your password: ");
   scanf("%c", passwd);

   printf(" n");

   if (uname == "waw" && passwd == "wow"){
      printf("You have logged inn");
   } else {
      printf("Failed, please try againn");
   }
   return 0;
}

log.c: In function ‘main’:
log.c:7:10: warning: format ‘%c’ expects argument of type ‘char *’, but     argument 2 has type ‘int’ [-Wformat=]
    scanf("%c", uname);
          ^
log.c:9:10: warning: format ‘%c’ expects argument of type ‘char *’, but     argument 2 has type ‘int’ [-Wformat=]
    scanf("%c", passwd);
          ^
log.c:13:14: warning: comparison between pointer and integer
    if (uname == "waw" && passwd == "wow"){
              ^
log.c:13:33: warning: comparison between pointer and integer
    if (uname == "waw" && passwd == "wow"){
                                 ^

#include <stdio.h>

int main(){
   int res;
   char uname[40];   // char arrays instead of single char
   char passwd[40];

   printf("Enter your username: ");
   res = scanf("%39s", uname);  // Set a maximum number of chars to read to avoid overflow
   if (res != 1) exit(1); // Error on stdin
   printf("Enter your password: ");
   res = scanf("%39s", passwd);
   if (res != 1) exit(1); // Error on stdin

   printf(" n");

   // Use strcmp
   if ((strcmp(uname, "waw") == 0) && (strcmp(passwd, "wow") == 0)){
       printf("You have logged inn");
   } else{
       printf("Failed, please try againn");
   }
   return 0;
}

char *uname, *passwd;

uname = malloc(X);      //where X is the number of bytes you want to allocate for uname
if (uname == NULL)
    printf ("Error allocating memory for uname.");
passwd = malloc(Y);      //where Y is the number of bytes you want to allocate for passwd
if (passwd == NULL)
    printf ("Error allocating memory for passwd.");

#define MAX_LENGTH_UNAME X  //where X is the maximum length for uname, for instance 25
#define MAX_LENGTH_PASS Y   //where Y is the maximum length for passwd, for instance 20
....
char [MAX_LENGTH_UNAME] uname;
char [MAX_LENGTH_PASS] passwd;

scanf("%s", uname);
scanf("%s", passwd);

if ( (strcmp(uname, "waw") == 0) && (strcmp(passwd, "wow") == 0) ) {
   printf("You have logged inn");