I need help debugging a basic C program to calculate Fibonacci numbers - c

Question

#include <stdio.h>
int main();
{
int a;
int b;
int c;
a = 1;
b = 1;
c= 2;
for ()
{
a = c + b;
printf(a,"\n");
b = c + a;
printf(b,"\n");
c = a + b;
printf(c,"\n");
}
}
I am a beginner at C and am trying to write a program to list the Fibonacci sequence.
This is what I have so far. I know I have at least two issues, one being the for loop. How would I make it an infinite loop?
My second issue that I'm running into is this error message
"prog.c:3:1: error: expected identifier or '(' before '{' token
{
^"
If someone could help that would be much appreciated.

Answer 1

Remove the ; after int main() -- should take care of the compiler error
while(1) instead of for() -- will run an infinite loop

Answer 2

Here is the working code for Fibonacci series
#include <stdio.h>
void main()
{
int a;
int b;
int var_z;
a = 1;
b = 1;
for(int i = 0;i < 10;i++)
{
printf("%d\n",a);
printf("%d\n",b);
a = a+b;
b = a+b;
}
}
Eg. https://eval.in/1013468

Answer 3

/* Fibonacci series */
#include
int main()
{
long int a =0;
long int b=1;
long int c=1;
int n,d=1;
printf(" Enter the number of
terms ");
scanf("%d",&n);
do
{
printf("%d\n",c);
c=b+a;
a=b;
b=c;
d=d+1;
}
while(n>=d);
return 0;
}

Answer 4

This is one way you might do it.
#include <stdio.h>
int main()
{
unsigned int a;
unsigned int b;
unsigned int c;
a = 0;
b = 0;
c = 1;
while(1)
{
if (c < b)
break;
printf("%u\n",c);
a = b;
b = c;
c = a + b;
}
}
Modified to use unsigned int and change comparison based on comment.
Bobby

Answer 5

How to read this particular compiler error:
prog.c:3:1: error: expected identifier or '(' before '{' token { ^
This is telling you that the error occurs on line 3:
1: #include <stdio.h>
2: int main();
3: { // <------ compiler is complaining about this line
and that it's seeing a { where it shouldn't. The only time it should see a { is after a function declarator (function name plus argument list) or after an identifier (for a struct, union, or enum definition).
The problem is that you shouldn't have the semicolon after int main Because of it, the compiler is treating int main() as a declaration, not the beginning of a function definition.
Remove that semicolon and the error will go away.
Important lesson here - the compiler doesn't tell you where you actually made the error, but where that error prevents it from translating the code. If you have a deeply nested loop, like
for (...)
{
for (...)
{
for (...)
{
and you forget to put in the closing brace on the innermost loop, the compiler won't say "you forgot to put a closing brace on this innermost loop"; instead, it will complain about a line some ways down, either because it's reached the end of the program or the next function definition without seeing the closing } of the previous function.
How would I make it an infinite loop?
The syntax for an infinite loop is either while(1) or for(;;). Doesn't matter which you use, the compiler should (should) generate the same code for both. Like other people have said, though, Fibonacci numbers get very large very quickly, too large for a native integer data type to represent. You'll start seeing overflow errors after computing the 50th F number or so.

Answer 6

There are some errors with your code, the semi colon after main is wrong, your algorithm dont output fib sequence and the for loop it is typed incorrect.
#include <stdio.h>
int main() //;<-- doesn't contain semicolon
{
/* use a better variable name for clarity
int a; --> a
int b; --> last number
int c; --> sum
a = 1;
b = 0;
*/
int a = 1;
int last = 0;
int sum;
for (;;) // infite for loop needs 2 semicolons to work
{
printf("fib : %d\n", last);
sum = a + last;
last = a;
a = sum;
}
}
By the way, you should limit your for loop or else it going to overflow your int variable. long unsigned a,sum,last would give you more bits to store.