#include<stdio.h>
#include<conio.h>
#include<windows.h>
#define ENTER 13
#define TAB 9
#define BCKSPC 8
struct user{
char fullName[50];
char email[50];
char password[50];
char username[50];
char phone[50];
};
void takeinput(char ch[50]){
fgets(ch,50,stdin);
ch[strlen(ch) - 1] = 0;
}
char generateUsername(char email[50],char username[50]){
for(int i=0;i<strlen(email);i++){
if(email[i] == '@') break;
else username[i] = email[i];
}
}
void takepassword(char pwd[50]){
int i;
char ch;
while(1){
ch = getch();
if(ch == ENTER || ch == TAB){
pwd[i] = '\0';
break;
}else if(ch == BCKSPC){
if(i>0){
i--;
printf("\b \b");
}
}else{
pwd[i++] = ch;
printf("* \b");
}
}
}
int main(){
system("color 0b");
FILE *fp;
int opt,usrFound = 0;
struct user user;
char password2[50];
printf("\n\t\t\t\t----------Welcome to authentication system----------");
printf("\nPlease choose your operation");
printf("\n1.Signup");
printf("\n2.Login");
printf("\n3.Exit");
printf("\n\nYour choice:\t");
scanf("%d",&opt);
fgetc(stdin);
switch(opt){
case 1:
system("cls");
printf("\nEnter your full name:\t");
takeinput(user.fullName);
printf("Enter your email:\t");
takeinput(user.email);
printf("Enter your contact no:\t");
takeinput(user.phone);
printf("Enter your password:\t");
takepassword(user.password);
printf("\nConfirm your password:\t")
takepassword(password2);
if(!strcmp(user.password,password2)){
generateUsername(user.email,user.username);
fp = fopen("Users.dat","a+");
fwrite(&user,sizeof(struct user),1,fp);
if(fwrite != 0) printf("\n\nUser resgistration success, Your username is %s",user.username);
else printf("\n\nSorry! Something went wrong :(");
fclose(fp);
}
else{
printf("\n\nPassword do not matched");
Beep(750,300);
}
break;
case 2:
system ("cls");
char username[50],pword[50];
struct user user;
printf("\nEnter your username:\t");
takeinput(username);
printf("Enter your password:\t");
takepassword(pword);
fp = fopen("Users.dat","r");
while(fread(&user,sizeof(struct user),1,fp)){
if(!strcmp(user.username,username)){
if(!strcmp(user.password,pword)){
system("cls");
printf("\n\t\t\t\t\t\tWelcome %s",user.fullName);
printf("\n\n|Full Name:\t%s",user.fullName);
printf("\n|Email:\t\t%s",user.email);
printf("\n|Username:\t%s",user.username);
printf("\n|Contact no.:\t%s",user.phone);
}
else {
printf("\n\nInvalid Password!");
Beep(800,300);
}
usrFound = 1;
}
}
if(!usrFound){
printf("\n\nUser is not registered!");
Beep(800,300);
}
fclose(fp);
break;
case 3:
printf("\t\t\tBye Bye :)");
return 0;
}
getch();
} Write, Run & Share C Language code online using OneCompiler's C online compiler for free. It's one of the robust, feature-rich online compilers for C language, running the latest C version which is C18. Getting started with the OneCompiler's C editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose language as 'C' and start coding!
OneCompiler's C online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample C program which takes name as input and print your name with hello.
#include <stdio.h>
int main()
{
char name[50];
printf("Enter name:");
scanf("%s", name);
printf("Hello %s \n" , name );
return 0;
}
C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.
When ever you want to perform a set of operations based on a condition if-else is used.
if(conditional-expression) {
// code
} else {
// code
}
You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.
Switch is an alternative to if-else-if ladder.
switch(conditional-expression) {
case value1:
// code
break; // optional
case value2:
// code
break; // optional
...
default:
// code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition.
for(Initialization; Condition; Increment/decrement){
// code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while(condition) {
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (condition);
Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.
data-type array-name[size];
data-type array-name[size][size];
Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.
Two types of functions are present in C
Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,
User defined functions are the ones which are written by the programmer based on the requirement.
return_type function_name(parameters);
function_name (parameters)
return_type function_name(parameters) {
//code
}