Class 34: Strings

Held: Monday, 1 November 2010

Summary: We begin to consider the design of strings in C.

Related Pages:

• EBoard.
• Lab: Strings.
• Reading: K&R 5.5, B3.

Notes:

• Reminder: NaNoWriMo and PragProWriMo start today.
• EC for MD's noontime talk. (Free pizza, too!)
• Story from Friday's lunch.
• Reading for Tuesday: K&R 5.6-5.9.
• Are there questions on Exam 2?

Overview:

• About strings.
• Important string functions.
• Thinking like a C programmer.
• Lab.

Strings

• In C, strings are null-terminated arrays of characters.
  • "null" means "0".
• Since arrays are (mostly) interchangable with pointers, strings are also pointers to characters.
• While this sounds simple, it's easy to screw things up.

Important String Functions

• strlen (str) - find the number of characters in str.
• strcpy (target, source) - copy string from source to target.
• strncpy (target, source, n) - copy up to n characters from source to target.
• strcat (target, source) - put source on the end of target.

Thinking Like a C Programmer

/**
 * strcpy: Copy source (s) to target (t).
 */
void 
strcpy (char *t, char *s) 
{
  char *result = t;
  while (*t++ = *s++)
    ;
  return result;
} // strcpy

Lab

• Do the lab.