C Structures

1
C Structures
2
A first C Program

• include ltstdio.hgt
• void main ( void )
• float height, width, area, wood_length
• scanf ( "f", height )
• scanf ( "f", width )
• area 2 height width
• wood_length 2 ( height width ) 3.25
• printf ( "The area of glass is f metres.\n",
  area )
• printf ( "The length of wood is f feet.\n",
  wood_length )

3
Structures of program Explained

• include- Not a part of the program. Tells the
  compiler to get something contents of a file
  needed for the program
• stdio.h standard input/output library
• ltgt- tells the compiler to look in the system area
  as opposed to the current directory
• Void a keyword denoting nothing, tells the
  compiler that main returns nothing
• Main- a special function. This function is ran at
  compilation time
• (void)- tells the compiler that main works on
  nothing i.e. it has no parameters
• - brace divides the program into blocks.

4

• Float- a variable type used to store values.
  Three types, floats, integers and characters.
• - needed at end of all declarations in C, to
  keep compiler on track. Missing one causes
  tremendous errors.
• Scanf- (scan formatted) function used for file
  input.
• The parameters are placed in brackets.
• f - tells the compiler that everything
  inside is used to denote th string. tells the
  compiler we are giving the format of a number and
  f tells the compiler it is of the float type.
• height C does not allow the value of a
  parameters value to be changed. tells the
  compiler to create a pointer to the given
  Variable, pass it to scanf

5

• area2 heightwidth - this is an assignment,
  the result of the expression is placed in area.
• Printf does the opposite if scanf (prints to
  console)
• "The area of glass needed is f metres.\n",
  area)- The text is printed as is without
  dilimiters
• f tells the compiler a float will be printed,
  and the variable area tells the compiler what
  float to print
• Other types
• d signed decimal ineteger
• c print a character
• 5d- decimal to five character positions
• 6.2 f floating point to 6 characters, right
  justified
• \n- move to new line

6
Variables and data

• Int variables- ranges from -32768 to 32767 with
  no fractional parts
• Float varibles real numbers of varying
  precision -3.4E-38 to 32767
• Char variabes- can hold a single character
• C does not provide Strings, Booleans

7
Declare A variable and assign values

• int first
• float second
• char comma
• Type variablename
• first 100
• second100.1
• char l

8
More Variables

• typedef- Allows users to change the name of a
  standard data type.
• enum- Enumerated data types enum
  colorred,blue,white
• struct-
• Structures are heterogeneous user-defined
  datatypes
• used to create nodes and lists
• e.g. Struct bodyparts
• int feet
• double weight
• char5 eye_color

9
Magic Numbers

• These are constants that can not be changed in a
  program e.g. array sizes, character positions,
  conversion factors, pi
• They should have their own names
• We use the directive define to manage magic
  numbers e.g.
• define pi 3.14159
• Now whenever the compiler sees pi it will send
  3.14259

10
Expressions, Operands and Operators

• Expressions are made from Opereands and operators
• Operands things to work on i.e. variables
• Operators the workers.
• E.g. 2 4

11
Operators and Precedence

• In Highest Priority order
• - unary minus Makes number negative
• multiplication
• / division
• addition
• - subtraction
• Use parenthesis to change precedence
• A note ½ is not the same as ½.0 ..to overcome we
  use
• int i 3, j 2
• float fraction
• fraction (float) i / (float) j
• printf ( "fraction f\n", fraction )

12

• Conditional If
• if (condition)
• statement or block we do if the condition is
  true
• else
• statement or block we do if the condition is
  false

13

• Relational Operators
• is equal
• ! not equal
• lt less than
• gt greater than
• lt less than or equal to
• gt greater than or equal to
• ! Not - used for inverting
• combine two statements that is both true
• or one of the statements is true

14
Loops

• do while - ran exactly one or more times
• do
• Statement or block
• while (condition)
• E.g
• Do
• printf ( "hello mum\n" )
• while (1)

15

• While Loop (runs 0 or many times)
• while (condition)
• Statement or block
• e.g. while(1)
• printf (hello mum)
• For loop repeats for a set number of times
• for ( i0 i ! 11 i i1 )
• printf ( "hello\n" )

16
Switch statement

• Takes a value and decides which option to perform
• Chooses the option that matches the case
  presented.

17
Switch statement(cont)

• void main (void)
• char selection
• printf ("\nEnter the type of window ")
• scanf ("c", selection)
• switch (selection) case '1' handle_casement
  ()
• break
• case '2' handle_standard ()
• break
• case '3' handle_patio ()
• break

18
Functions

• float get_ranged_value ( float min, float max )
  // header
• float temp
• do printf ( "Give the value " )
• scanf ( "f", temp )
• while ( (temp lt min) (temp gt max) )
• return temp // return variable
• Header tells the compiler that we are creating
  a function called get_ranged_value, that returns
  a float, and accepts two float values
• Return statement- tells the compiler what to send
  back to main

19
A note on arrays

• Basically a box od data with subscripts to each
  element
• Starts subscripts at 0
• Type arraynamenumber of ellements
• e.g int x10
• creates and empty array that can hold 10 integers
• The number 10 is the subscript of the array.
• The elements of the array are
• X0, x1x9

20

• Initializing an Array
• int main()
• short age4 23, 34, 65, 74
• return 0
• Or
• int main()
• short age4
• age023
• age134
• age265
• age374
• return 0

21

• Print an Array
• for(j0 jlt4 j)
• printf("d\n", same_agej)