Character Arrays

Strings: Mistake by Design?

  • Only what is necessary is built-in in C

  • From today’s point of view C is the language for hardware-oriented programming

  • Invented to keep UNIX portable, independent from PDP-11 assembler

  • ⟶ C itself is the language core - everything else belongs in libraries


  • Language core knows what string literals are

  • 7-bit ASCII sufficed at that time ⟶ no multibyte character sets, no need for Unicode

  • But: much later somebody claimed that “640K is enough”

Strings: Definition


  • Array of characters …

  • … terminated by a “null” character ('\0')

char a_string[] = "hello";

Strings: Library Functions

Functions from the standard library

  • strlen(const char[])

  • strcpy(char dest[], const char src[])

  • strncpy(char dest[], const char src[], int maxlen)

  • strcat(char dest[], const char src[])

  • strncat(char dest[], char src[], int n)

  • strcmp(const char lhs[], const char rhs[])

  • strncmp(const char lhs[], const char rhs[], int maxlen)

Many more ⟶ see manual page

Strings as Parameters

  • Strings (like arrays in general) are passed as pointers

  • Modifications visible to the caller

char a_string[] = "hello";
char another_string[10];
copy(another_string, a_string);

Strings: Dangers

Low level definition leads to errors

  • Copy: not enough memory allocated to hold the copy

  • Forget to null-terminate when composing strings by hand

  • … many many more …