Chapter 10, User Defined Data Types

• You should read chapter 10 for deep knowledge.
• The first part deals with Built in data types
  • You know most of these from 130.
    • integer types: what are they?
    • float types: what are they?
  • Characters are integer but:
    • Internally they are represented as 8 bit two's compliment numbers
    • Externally they are represented by their ascii code.
    • Look at the ascii table.
      • Notice 0, 1, 2, 3 ... are in order, so '0' < '1'
      • Notice A, B, C, ... are in order, so 'C' < 'Q'
      • Notice a,b,c ... are in order, so 'w' < 'z'
      • But 'Z' < 'a'
    • A common trick

      • char letter;
        
        letter = static_cast('a' + 4); 

      • Letter will contain 'e'
    • Look at numdist.cpp
    • So our conversions in hex could have been

    • IntDigitToHex(int digit) {
          char value;
          if (digit <= 10) {
             value = static_cast<char> (static_cast<int>('0') + digit);
          } else {
             value = static_cast<char> (static_cast<int>('A') + digit-10);
          }
          return value;
      }
                  

• These types are built in
• Sometimes called atomic