Lecture 4: C Strings

Chars

How can we represent chars in binary (and subsequently strings)?

• Basically, stored in ASCII which maps chars to integers. These integers are then stored in binary. As a result, we can have operators like equality.

• Sequentially ordered (lowercase a is 97 and lowercase b is 98).

• Lowercase letters are 32 more than their uppercase equivalents (bit flip!)
  • Bit flipping the 32's bit.

Strings

• An array of characters; no designated data type unlike char in C.

• How do we differ? Via a null terminator. Tells when string stops. Thus, always need to allocate extra space in the array for it.

• Strings are not objects so they do not embed additional information such as its length.

• Passed into functions and such via pointer reference (to the first char) so no need to copy.
  • We can still use char* and char[] in the same way though.

Concatenation and substrings

• Can't perform these two operations using HLPL commands such as +. Since it stores addresses.

• As such, we use a library function called strcat.
  • Removes old null terminator (of the first, declared string), adds new one at the end.