c - In which situation does function prototype have to include parameter names? -

i studying c programming language k&r , there exercise below:

exercise 3-5: write function itob(n, s, b) converts integer n base b character representation in string s. in particular, itob(n, s, 16) formats n hexadecimal integer in s.

so wrote program this:

#include <stdio.h> #include <string.h> #define maxline 1000  void reverse(char ); void itob(int , char , int );  main() {     char line[maxline];     int n, i;     printf("integer: ");     scanf_s("%d",&n);     printf("base: ");     scanf_s("%d",&i);     itob(n, line, i);     printf("%s", line); }  void itob(int n, char s[], int b) {     int i, sign;      if ((sign = n) < 0)         n = -n;     = 0;          {          n % b < 10 ? (s[i++] = n % b + '0') : (s[i++] = n % b + '7');     }     while ((n /= b) > 0);     if (sign < 0)         s[i++] = '-';     s[i] = '\0';     reverse(s); }  void reverse(char s[]) {     int c, i, j;       (i = 0, j = strlen(s)-1; < j; i++, j--)     {         c = s[i];         s[i] = s[j];         s[j] = c;     } } 

i thought ok. when ran program, got error after input integer , base values, below:

unhandled exception @ 0x10022050 (msvcr110d.dll) in exercise 3-5.exe: 0xc0000005: access violation reading location 0x000000ec.

so program had trouble function itob call.

and after 2 hour struggle debugging, found cause function prototype of reverse need include parameter name this:

void reverse(char s[]); void itob(int , char , int ); 

the change made added s[] in function prototype of reverse , program worked properly.

i confused because learned parameter names of function prototype optional. why parameter name have include in function prototype of reverse? , why function prototype of itob not need parameter name , there not pop-up error? ide visual studio 2012.

thanks everyone's time , help.

the code in question has number of bugs, many of compiler should have @ least warned about.

when copied code , compiled using gcc, without additional arguments, first error message was:

c.c: in function ‘main’: c.c:16:5: warning: passing argument 2 of ‘itob’ makes integer pointer without cast [enabled default]      itob(n, line, i);      ^ c.c:6:6: note: expected ‘char’ argument of type ‘char *’  void itob(int , char , int );       ^ 

the error message correct. declared itob second parameter of type char, called second parameter of type char* (resulting implicit conversion of array line).

later, define itob second parameter of type char[] (which, since it's parameter, of type char*). incompatible earlier declaration, , should have been flagged compiler.

to answer question in title, in standalone prototype (one that's not part of function definition), parameter names optional. these 2 prototypes equivalent , valid:

void itob(int, char, int); 

and

void itob(int x, char y, int z); 

personally specify parameter names because makes code clearer.

for prototype that's part of function definition, names required, because that's how parameter objects defined.

but first, fix errors in code.