Data Types in C++, Intro and Ints part 1

• C++ supports multiple types of data.
  • Simple data types are types which can not be broken down any further.
  • Structured data types are types which are composed of one or more data type.
• The simple types include
  • Integer types
  • Floating Point Types
  • Enumerated types
• The address types will be discussed later.
  • pointers
  • references
• The structured types include
  • Arrays a collection of homogeneous data.
  • Structures a collection of (potentially) heterogeneous data.
  • Classes a collection of data and functions.
• But what about strings?
  • Strings are actually an example of a class.
  • The data is probably an array of characters
  • But they have associated functions
  • Let's take a quick look at cppreference.com string page.
• With strings you can
  • Ask for the size (.size() or .length())
  • Do all forms of comparison
  • find substrings
  • extract substrings
  • And MANY other things.
• We will be back to take a closer look at strings later.
• Integers
  • These are whole numbers.
  • They always include 0
  • But they can include negative numbers.
• The basic type is int
  • This is usually a 32 bit number, but
  • It could be as small as 16 bits
  • And it could be larger.
  • A 32 bit integer is in the range $-2^{31}$ to $2^{31}-1$
• In general with n bits
  • The range is $-2^{n-1}$ to $2^{n-1}-1$
• Since this can change, we can ask for the value.
  • Old style defined in <limits.h>
  • New style,
    • #include < limits>
    • numeric_limits<type>
      • min(), max(), lowest()
      • Plus many others.
      • See this reference (we will use it again soon)
  • Take a look at intSize.cpp
• Memory can be a problem
  • Think about a simulation of galaxies colliding.
    • I saw an estimate of about 100 billion stars in a galaxy.
    • That is 100x10^9, or 100GB of data if we only use one int for each star.
    • We will probably need to scale that, but still that is quite a bit of data.
    • Could we use a "smaller" number to represent each?
• To deal with this, we have different integer types.
  • A short is the smallest regular integer type.
    • This is really a short int but that is not required.
    • It is at least 16 bits.
    • See this reference.
  • A long is the largest regular, but ...
    • Again, it is a long int
    • It is at least 32 bits.
  • But in 11, they introduced a long long int or just long long
• Also, if we know we only have positive integers
  • We can declare something to be unsigned
  • unsigned long long int, or unsigned long long
  • unsigned long int, or unsigned long
  • unsigned int
  • unsigned short int or unsigned short
  • Unsigned shifts the range of an n bit integer to be from 0 to $2^{n}-1$
• Wow that is too much, which do I use?
  • In most situations I use an int
  • If I want a really big number I use an unsigned long long
• Take a look at pi.cpp.