i admit im a noobie

im starting to learn from the most basic 10 line progams(meaning 10 or less lines of code) to the most complex programs like i shuld but i cant even get a very basic code to work so in this topic (this same topic every time) im gonna post my codes and see what im doing wrong

so heres #1 its supposed to multiply number "a" by number "b" then print the output... but instead it crashes after the first number

Code:

---

#include<stdio.h>
int main(void){
printf("enter a number hit return then repeat.\n");
int a;
a = scanf("%d" ,a);
int b;
b = scanf("%d" ,b);
printf("%d",a * b);
getchar();
getchar();
return 0;
}

---

please dont just hand me the edited code..... explane how i can avoid the mistake the next time



EDIT: im sorry for my last topic i stated 2 months ago i was so into the game that i didnt care at all but now ive seen how bad i was and about a month ago i quit the game perminantly and im trying to get a real life

You were kinda close there. Know that scanf returns an int equal to how many fields in the format string it was able to read.

But when you pass in arguments to scanf, they should be a memory address.

Code:

---

int a;
scanf("%d" , &a);
int b;
scanf("%d" , &b);

---

Your buffer-flushing code (two getchar()s) should be this:

Code:

---

int c;
while((c = getchar()) != '\n' && c != EOF);

---

See the FAQ: http://faq.cprogramming.com/cgi-bin/...&id=1043284392

You can read multiple values with scanf() at once:

Code:

---

scanf("%d%d", &a, &b);

---

Code:

---

printf("enter a number hit return then repeat.\n");

---

Actually, all the user has to do is put some sort of whitespace between the numbers. A newline will do, but so would a space or a tab or anything that isspace() returns true for.

Quote:

---

when you pass in arguments to scanf, they should be a memory address.

---

What you were doing was passing the values of the variables a and b (which are uninitialized, [somewhat] random values). scanf() needs to know where the variables are located in memory so it can put the value the user entered into it.

scanf() returns the number of fields successfully read in. So if you use scanf("%d%d", &a, &b), a good way to see if it worked would be to use

Code:

---

if(scanf("%d%d", &a, &b) == 2) {
    /* successfull */
}
else {
    /* error */
}

---

scanf() might not be successfull if, say, the user entered "large" instead of a number. A good way to handle an error like that would be to flush the input buffer using code in my previous post and try again:

Code:

---

while(scanf("%d%d", &a, &b) != 2) {
    int c;
    printf("Invalid number! Please try again: ");
    while((c = getchar()) != '\n' && c != EOF);
}

---

thank you so much i used

Code:

---

scanf("%d%d", &a, &b);

---

EDIT: thats stupid of me to even try to make it a full calculator....

but i have a question... how can i use the same code using "long double" instead of "int"

just as easy as changing the %d to %ld on each scanf and in your last printf

Quote:

---

Originally Posted by louis_mine

just as easy as changing the %d to %ld on each scanf and in your last printf

---

Hmmm. And what would you use for a long double?

hhmmm?? wasn´t that the original question??? I would use %ld

From the unix manpage ya?

Code:

---

      L      Indicates        that  the  conversion will be either efg and the next
              pointer is a pointer to long double or the  conversion  will  be
              dioux  and  the  next  pointer is a pointer to long long.        (Note
              that long long is not an ANSI C type.  Any  program  using  this
              will not be portable to all architectures).

---

Therefore the correct identifier is actually %Lf

Time to update your man page. long long is in fact an ANSI C type as of C99.


Quzah.

Thanks for the protip, I'll make sure to do that if I get Linux. That's not my document, it belongs to some school, because that's where Google found it.