Arrays, lengths, and terminated text

The idea

This chapter assumes loops and declarations. An array contains a fixed number of consecutive elements. Valid indexes begin at zero and stop before that count. For a local array object, dividing sizeof the array by sizeof one element computes its element count without assuming how many bytes the element type occupies. This calculation does not recover a length from a pointer parameter.

A C string is a character sequence ending in a zero character. An initialized array such as char label[] = "fern" includes storage for that terminator and can be edited within its bounds. A string literal is not writable storage merely because a pointer can refer to it. When copying or assembling text, the capacity must include the terminator as well as the visible characters.

#include <stdio.h>
#include <string.h>
int main(void){char label[]="reed"; label[0]='R'; printf("%s %zu %zu\n",label,sizeof label,strlen(label));}

Reed 5 4

The array occupies five char elements including the terminator. strlen counts the four characters before that terminator.