Expected declaration specifier in for loop

[mcoll2204]

#include <stdio.h>
#include <math.h>
main()
{
int n;
int k;
int j;

//gets user input for length of string
printf("Enter the value of n:");
scanf("%d", &n);
//stores user input as n

printf("Printing primes less than or equal to %d: \n", n);

for(k = 2; k <= n; k++)
{
if(is_Prime(k) == 1)
{
printf("%d,", k);
}
}


//here is the is_Prime function
int is_Prime (int k)


for(j = 2; j < k; j++)
{
if(k%j != 0)
{
return 1;
}

else(k%j == 0)
{
return 0;
break;
}
}

When I compile my code I get an error saying that I need declaration specifiers in my is_prime subroutine in the for loop. Can anyone explain what this means or how to fix it? Here is the line of code it references.

for(j = 2; j < k; j++)

[weaknessforcats]

You are calling is_prime before you have defined it. The compiler doesn't know whether is_prime is a valid call.

Either move the definition of the function above main() or place a function prototype above main to reasuure the compiler.

BTW: main() is returning default int. main() should return an int.

[donbock]

You need to declare variable j before you use it.

You have a parenthesized expression in the else statement in is_Prime. But else does not have a condition argument. Perhaps you mean this to be a comment.