Data Types, Simple IO, Operators, Casts

1
Data Types, Simple I/O, Operators, Casts
Decisions

• Chapters 6 - 9

2
Integer Data Types

• Short 16 bits
• -32,768 to 32,767
• Unsigned Short 16 Bits
• 0 to 65,535
• Long 32 Bits
• -2,147,483,648 to 2,147,483,647
• Unsigned Long - 32 Bits
• 0 to 4,294,967,295
• Long Long 64 Bits
• /-9.2233720 X 1018
• Unsigned Long Long 64 Bits
• 0 to 1.8446744 X 1019
• Char 8 bits
• -128 to 127
• Unsigned Char
• 0 to 255
• Int
• Depends on the compiler either short or long.
  Instead, you should use short or long explicitly.

3
Floating Point Data Types

• Float 32 bits
• -1.2 x 1038 to 3.4 x 1038
• Double 64 bits
• -2.2 x 10308 to 1.8 x 10308

4
Constants

• Any sequence of only the digits 0-9 and not
  starting with a 0 is considered a decimal integer
• Any sequence of digits beginning with a 0 is
  considered an octal int
• Any sequence of digits or letters a-f starting
  with a 0x or 0X is considered a hexadecimal
  integer
• Adding a trailing L to any of the preceding
  constants promotes the int to a long. ie 20L
• A character constant is a single character
  surrounded by single quotes.
• Any sequence of digits containing a decimal point
  is considered a double constant
• Any sequence of digits containing a decimal point
  and ending with an f or F is considered a
  float constant.
• A string constant is any sequence of characters
  or digits surrounded by double quotes.

5
Variables

• Rules to live by
• All variables must begin with a letter or the
  underscore character.
• Subsequent characters may be letters, digits, or
  the underscore character.
• No special characters other than the underscore
  are allowed.
• Variables must be defined before they can be
  used. You can define and assign a value at the
  same time. ie short temp35

6
Operators

• Mathematical
• addition
• - subtraction
• multiplication
• / division
• modulus
• Unary Operators
• increment
• -- decrement
• address of
• pointer dereference
• (type) cast operator
• (int)temp

• Boolean
• equals
• ! not equal
• greater than
• greater or equal
• ! not

7
Decisions

• If-else
• Done exactly the same way as in JAVA nuff said
• Switch
• switch (expression) case constant1 statement
  s break case constant 2 statements brea
  k etc default statements break

8
Switch Example

• short temp
• switch (temp) case 1 statements break c
  ase 2 statements break default printf(
  temp value wasnt either 1 or 2) break

9
Important things to remember when using decisions

• C will allow you to use an assignment operator
  () inside an if or switch even if you meant to
  use an equality operator (). Be very careful
  to double check youre using the right operator
  in your decisions.
• You must use break statements in your switches at
  the end of each case. If youre missing the
  breaks, execution will continue until it hits a
  break regardless of whether theyre inside
  another case statement.

10
Example of a missing break

• short temp
• switch (temp) case 1 statements break c
  ase 2 statements default printf(temp
  value wasnt either 1 or 2) break

If temp is 1, only thesestatements will execute
If temp is 2, these statements willbe executed,
but so will the printf statement because case 2
ismissing its break statement.
11
Output

• printf
• You already know printf will print a string
  constant to the screen, but how do you print out
  variables?
• printf(formatting string, arg1, arg2, arg3,
  etc)
• The formatting string is a string constant with a
  place-holder for each variable you wish to add to
  the output.
• Place-holders all begin with a and specify the
  type of variable to be printed. See the next
  slide for a list of place-holders.
• There is a one to one relationship between
  place-holders and arguments. The first
  place-holder will be replaced with the first
  argument, the second place-holder will be
  replaced by the second place-holder etc.

12
Output Placeholders

• d decimal integer
• u unsigned integer
• o octal integer
• x hexadecimal (small letters)
• X hexadecimal (uppercase letters)
• c ASCII character
• s string

• f decimal
• e scientific notation
• g automatically selects either decimal or
  scientific notation based on size of variable
  being printed
• p print the address of a pointer in
  hexadecimal notation

13
Input From Keyboard

• scanf
• Scanf, is much like printf in that it takes a
  format string, and variable arguments.
• Scanf(format string,arg1,arg2, etc)
• The arguments to scanf MUST be memory addresses.
  Pointers and arrays (and therefore strings) are
  already memory addresses, so nothing needs to be
  done to them before they are passed to scanf.
  For other types of variables, you must prepend
  the address operator () to your variable name.
• If you have two shorts declared as a and b, the
  scanf command to fill them would bescanf(d
  d,a,b)
• A single space in the format string of scanf will
  accept any number of white space characters. You
  never want to end your format string with a
  space, otherwise your program will never exit the
  scanf call.

14
Input Place-holders

• d decimal integer
• o octal integer
• x hexadecimal
• X hexadecimal
• c ASCII character
• s string

• f decimal
• e scientific notation
• g either decimal or scientific notation

You can put an l after the percent sign in any
integer or float placeholder to convertthe input
into a long integer or float respectively. Ie
ld or lf. You can put an hafter the percent
sign to force the use of a short integer. Ie
hd. There is noshort float, so using the h
with any float type has no effect.