C programming Question on Characters

[User 14065453]

/*Write a programme to check a password if it has an uppercase letter, a digit and a special symbol. (I have provided what I have done and I am not getting the output as required. Need explanation on where I messed it up.)*/ #include #include #include int main() { int i; int tuna; do{ printf("Enter a password:%c \n", tuna); scanf(" %c", &tuna); } while( tuna != (isupper(tuna), isalpha(tuna), isdigit(tuna)) ); return 0; }

[David Crow]

I see several things wrong with your approach: 1) The first time through the loop, tuna is uninitialized so the printf() statement is going to print an incorrect character, 2) The scanf() statement is expecting to receive a char (%c) but you are giving it the address of an int, 3) The isupper(), isalpha(), and isdigit() functions return a non-zero value if the parameter is an uppercase alphabetic letter, and zero otherwise. You are then comparing this to tuna. While syntactically correct, it is nonsensical, 4) If your password is to hold numbers, letters, and symbols, the password type should not be an int, but should probably be a string. Consider something like:

int reqd = 0;
char pwd[32];
printf("Enter a password: ");
scanf("%s", pwd);
for (int x = 0; x < strlen(pwd); x++)
{
if (isupper(pwd[x])) // this does not check for special characters
reqd |= 0x1;
else if (isalpha(pwd[x]))
reqd |= 0x2;
else if (isdigit(pwd[x]))
reqd |= 0x4;
}

if (reqd == 0x07)
printf("Requirements have been met.\n");
else
printf("Requirements have NOT been met.\n");

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

[User 14065453]

I didn't get the logic behind "reqd" in the if else part. Can you please explain?

[jschell]

Your code is entering a character (singular) then checking it. You need to enter a word (multiple characters) and THEN check that entire word for one character of each type.

[jschell]

I presume this is for a class and I suspect you have not been taught bit manipulation. Unless you learn about it yourself, you probably do not want to hand in a solution that uses it.

[David Crow]

jschell wrote:

Unless you learn about it yourself, you probably do not want to hand in a solution that uses it.

Good point. I didn't think through my offering well enough.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

[David Crow]

You could (possibly) simplify to something like:

int upper = 0;
int alpha = 0;
int digit = 0;

...
if (isupper(pwd[x])) // this does not check for special characters
upper = 1;
else if (isalpha(pwd[x]))
alpha = 1;
else if (isdigit(pwd[x]))
digit = 1;

...
if (upper == 1 && alpha == 1 && digit == 1)
printf("Requirements have been met.\n");
else
printf("Requirements have NOT been met.\n");

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles