C integer/float array strange behavior -

okay fooling around making random programs , seeing outputs understanding how things work , noticed strange thing integer/float arrays. unlike char array '\0' character not stored directly after last entered element array. in integer array stored 2 elements after last element , in float 4 elements. here's code demonstrate strange fact. please me understand why happens.

#include <stdio.h> #include <string.h>  void foo(int* x) {     while ( *(x) != '\0' )     {         printf("%i ",*x);         ++x;     } }   void foo1(float* x) {     while ( *(x) != '\0')     {         printf("%.1f ",*x);         ++x;     } }   void foo2(char* x) {     while( *(x) != '\0' )     {         printf("%c",*x);         ++x;     } }   int main(void) {     int a[4] = {1,2,3,4};     float b[4] = {1.1,2.2,3.3,4.4};     char name[] = "muneeb";      foo(a);     printf("\n\n");      foo1(b);     printf("\n\n");      foo2(name);     return 0;   } 

output:

1 2 3 4 -12345677723 -1623562626 1.1 2.2 3.3 4.4 0.0 0.0 0.0 0.0 -0.0 -1.3 

in general, there no 0 element after end of array. cannot assume there is; kind of code segfault. finding 0 there coincidence.

in char arrays in particular, rule same. however, literal string "hello, world!" 1 char longer you’d counting characters. equivalent to unmodifiable char[13] of {'h', 'e', 'l', 'l', 'o', ',', ' ', 'w', 'o', 'r', 'l', 'd', '!', '\0'}. lot of library functions working chars expect terminating '\0'; no such expectation exists other types of arrays , need pass length explicitly.

also note *(x) != '\0' treats '\0' int or float zero, , equivalent *x != 0 or *x != 0.0f (for different types of x in different functions). if had stored actual 0 in 1 of arrays, have counted that.

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since there no special sentinel convention int or float arrays (because 0 , 0.0f reasonable values put in array), should create separate size_t variable keep track of array’s length. then, if ever need create function acting on array, can give length parameter , have iterate that. example:

void foo(int* x, size_t length) {      (size_t = 0; < length; ++i)     {         printf("%i ", x[i]);     }  }  

(i use size_t here because typically represents size of structures in memory).

then can call foo(a, 4);. if need variable-sized array, can create size_t a_length variable when create a, , update whenever a’s size changes.

you might want char arrays sometimes, such if have binary data might contain 0 bytes, or because scanning end of string takes time , don’t need @ each character.