How do I deal with string input in C? -

i'm practicing c , make simple login program username , password... here code:

int main(){    char uname, passwd;     printf("enter username: ");    scanf("%c", uname);    printf("enter password: ");    scanf("%c", passwd);     printf(" \n");     if (uname == "waw" && passwd == "wow"){       printf("you have logged in\n");    } else {       printf("failed, please try again\n");    }    return 0; } 

and got error when try compile it

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

there no string data type in c programming language. strings in c represented array of characters.

in c, char data type represent character. so, need declare array of char data type represent string in c. each element in array hold character of string.

also, operators in c ==, !=, +=, + defined build-in data types in c , since, there no operator overloading in c, can't use these operators c-string c-strings not build-in data type in c programming language.

note: c-strings null-terminated array of char data types. means, last character in c-string in c used store null character ('\0') marks end of string.

the header file <string.h> has predefined functions can use operate on c-string(null-terminated array of char data type). can read more on here.

so, program should like:

#include <stdio.h> #include <string.h>  #define cstr_max_len 100 int main() {     char uname[cstr_max_len+1];   //an position store null character if 100 characters stored in it.     char passwd[cstr_max_len+1];      printf("enter username: ");     scanf("%s", uname);        printf("enter password: ");     scanf("%s", passwd);      // use strcmp compare values of 2 strings.     // if strcmp returns zero, strings identical     if ((strcmp(uname, "waw") == 0) && (strcmp(passwd, "wow") == 0)){          printf("you have logged in\n");     } else{          printf("failed, please try again\n");     }     return 0;  } 

remember, correct format specifier handle c-strings %s in c programming language. so, have change scanf() function call. also, have used strcmp() function declared in header file <string.h> (i have included header file in above program). returns numeric 0 if strings match. can read more above here. also, have @ strncmp() safer version of strcmp(). also, remember can lead undefined behavior if try access array out of it's bound. so, idea include checking in program. as, included in answer can change scanf() function call to:

scanf("%100s", uname); 

it avoids read more 100 characters in array uname allocated store 100 characters(excluding null character).