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

Contradiction:

• 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

String

• 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 …