C Programming Tutorial by Examples

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C Programming Tutorial by Examples

• Dr. Kalim Qureshi

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Introduction

• C is a system programming language.
• C programs are comparable in efficiency to
  assembly language programs.
• The source text of a C program can be distributed
  among several files, each of which can be
  compiled independently.
• Full type checking is not possible.
• The predefined data types are int, char and float
  together with short and long and double.
• User-defined types are enumeration types, arrays
  and structure

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Structure of C Program

• Preprocessor directives
• main()
• Variable declarations
• Statements
• A simple C Program 1
• main ()
• printf (hello, world)

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Sample Program 2

• include ltstdio.hgt //preprocessor directive
• define PI 3.14159 / Directive for creating
  constant /
• int main (void) //main function
• double radius, area circum //variable
  declaration
• / get the circle radius /
• print( Enter radius )
• scanf (lf, radius)
• / Calculate the area /
• area PI radius radius
• / calculate the circumference /
• circum 2 PI radius
• / Display the area and circumference /
• printf (The area is f\n, area)
• printf (The circumference is f\n, circum)
• Enter radius 5.0
• The area is 78.539750
• The circumference is 31.415900

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Preprocessor Directives

• Syntax
• includeltstandard header filegt
• e.g.
• includeltstdio.hgt
• includeltmath.hgt
• Directives for creating constant
• Syntax
• define NAME value
• e.g.
• define PI 3.141593
• define MILES_PER_KM 0.62137

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Sample Program 3

• To find addition of two numbers
• include ltstdio.hgt //preprocessor directive
• main () //main function
• int number1, number2, sum //variable
  declarations
• printf (Please input two numbers )
• scanf (d d, number1, number2)
• sum number1 number2
• printf(The sum of two numbers is d, sum)

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Sample Program 4

• To displays the users nickname and current year
  in a welcoming message
• include ltstdio.hgt
• int main (void)
• char letter_1, letter_2, letter_3, letter_4,
  letter_5
• int year
• printf(Enter a 5-letter name and press return
  )
• Scanf(c c c c c, letter_1, letter_2,
  letter_3, letter_4, letter_5)
• printf (Enter the current year and press
  return)
• scanf (d, year)
• Printf(Welcome, ccccc . d is a great year
  to study C!, letter_1, letter_2, letter_3,
  letter_4, letter_5)
• return (0)
• Enter a 5-letter name and press return Kalim
• Enter the current year and press return 2004
• Welcome, Kalim . 2004 is a great year to study C!

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Reserved Key Words

• All reserved keywords in C language appears in
  lower case they have special meaning in C and
  cannot be used for any other purposes at any
  place.
• E.g. int, char, void, double, return etc.
• Syntax for variable declaration
• int varible_list
• double varible_list
• char varible_list
• float varible_list

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Rules for Making an User Define
Identifier/Variable name

• An identifier name can not begin with a digit.
• An identifier name must consist only of letters
  digits, or underscores.
• A C reserved key word (e.g. return, double, int
  etc.) cannot be used as an identifier name.
• An identifier defined in a C standard library
  (e.g printf, scanf) should not be redefined.
• For example 4 name, int, two-by-four, scanf are
  invalid identifier name.

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scanf and printf functions

• Syntax
• scanf ( format, input list separated by coma)
• e.g. scanf (d c age, first_initia)
• Syntax
• printf (format, print list)
• e.g. printf(I am d years old, and my GPA is
  f\n, age, gpa)
• char c
• int d
• float f
• double lf

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Function with Input Parameter /Argument

• The general form for function definition
• function_return_type function name (parameter
  list separated by commas )
• Example int sum (int x, int y)
• void abc (void)
• void abc (int x, float y, double d, int a)
• int abc (int b, double k, char p)
• float abc (int g, char h, double r)

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Function with Input Parameter /Argument

• / Function with Input Arguments and a Single
  Result /
• includeltstdio.hgt
• void print_rboxed(double rnum) // User defined
  function
• printf("\n")
• printf(" \n")
• printf(" 7.2f \n", rnum)
• printf(" \n")
• printf("\n")
• // end of print_rboxed user defined function
•  
• void main( ) // calling function
• actual
  parameter
• print_rboxed(2.24567) // function call
•  
• // end of main

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/ Function to find larger of two numbers /

• includeltstdio.hgt
•  
• double bigger(double n1, double n2) // function
  definition
• double larger // variable declaration
•  
• if(n1gtn2)
• largern1
• else
• largern2
• return (larger) // returns value of larger to
  calling plaice in main function
•  
• // end of bigger function

• void main( )
•  
• double number1,number2, max // variable
  declaration
• printf("Please input two numbers ")
• scanf("lf lf", number1, number2) // input
•  
• max bigger(number1, number2) // function call
•  
• printf("The max of lf and lf is
  lf",number1,number2,max)
•  
• // end of calling main function

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Pointer

• Pointer variable is a special variable which
  stores the address of other variable. If a
  pointer variable stores the address of a char
  variable , we call it a character pointer and so
  on.
• To handle pointers in C language we use two unary
  operators ,
• Address operator (ampersand symbol)
• Pointer operator OR Indirection
  operator OR Value at address.
• Examples
•  
• int j --------? Means the value at address
  contained in j is an int OR in other words j is
  an integer pointer.
• int k ------? Means the value at address
  contained in k is an int.

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Pointer (Cont. )

• Example1
• includeltstdio.hgt
• char gz
• int main(void)
• char ca
• char ppc
• printfc\n,p)
• pg
• printf(c\n,p)
• return 0

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Pointer (Cont.)

• includeltstdio.hgt
• void myfunction(int a, int b, int c, int sum,
  int prod, float average) // function
• sumabc
• prod abc
• average(abc)/3.0
• // end of function
• int main (void) // main program or main function
• int x,y,z,su_m,product
• float av_g
• printf("Enter three integer input parameters a,
  b and c ")
• scanf("d d d",x,y,z)
•  
• myfunction(x, y, z, su_m, product, av_g) //
  function call
•  
• printf("
  ")

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Array

• define SIZE1 10
• define SIZE2 100
• int arriSIZE1
• float arrfSIZE2
• Example
• double abc50
• int n
• for (n 0 n lt 50 n)
• printf (The dth element of array
  is lf\n, n, abcn)
•  Array Initialization
• int vector 5 12, 67, -56, 89, 1
• float xyz 8 1.5, 7.8, 5.6, -9.55, 0.5,
  8.4
• char ccc 4 r, 4, , s
• int sss 12, 45, 78

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Array with Function

• printf("\nthe sum of first three array elements
  is d", total)
• // end of main
• int sum_elements( int a, int b, int c ) //
  Function header
• int sum
• sumabc
• return (sum)

• includeltstdio.hgt
• int sum_elements(int a , int b, int c) //
  Function Prototype
• void main()
• int x10, total
• x010 x120 x230
• total sum_elements( x0, x1, x2 )
  //Function call to compute sum
• printf("For the array values d d d\n", x0,
  x1, x2 ) // Output results

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How to pass whole array as a parameter in
Function

• Unlike simple variables, array is not passed into
  a function, but rather its address is passed.
• This is done by specifying the array name
  followed by brackets (size is not necessary).

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How to pass whole array as a parameter in Function

• include ltstdio.hgt
• define SIZE 4 // defining the size of the array
  as 4 .
• int max (int arr ) // declaring the
  function max which returns integer value and
  accepts an
• // integer
  array called arr
•  
• void main (void)
• int arr SIZE , j , big //declaring the array
  arr along with other variables
•  
• for ( j 0 j lt SIZE j ) //using for loop
  to read the array
• printf ("Enter the dth element of array ",
  j )
• scanf ( "d", arrj )
• // end of for
•  
• big max ( arr ) //calling the function max
  by passing the array with only name
• printf ("\nThe maximum value is d\n", big )
•  
• // end of main

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How to pass whole array as a parameter in Function

• int max ( int arr ) /function declaring that
  it accepts integer array arr as its input/
• int j , big 0
• for ( j 0 j lt SIZE j ) /using for loop
  to find the maximum number of array arr/
• if ( arrj gt big )
• big arrj
•  
• // end of for loop
• return (big) //returning the maximum value
•  
• //end of max function

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Structure

• The struct (structure) specifier is used to
  declare a data structure that can store
  heterogeneous data elements.
• The elements can be of any type including
  enumerated types, arrays and even other
  structures.
• E.g
• struct user_record
• int id_no
• char name40
• char dept40
• int no_of_books
• A variable with the above structure can be
  declared as
• struct user_record user

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Structure (Cont.)

• Typedef
• Look at the following statement
• Typedef long double F
•  
• Once this is done we can use F wherever we intend
  to use long double.
•  
• E.g F a,b,c

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Structure (Cont. )

• We can simplify the variable declaration above,
  if we use typedef in the declaration. The above
  can then be defined as
• E.g typedef struct
• int id_no
• char name40
• char dept40
• int no_of_books
• USER_RECORD
•  
• The variable declaration then becomes
• USER_RECORD user
• Once a variable is declared, we can access the
  individual elements (called fields) of the record
  using the dot (.) operator.

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Structure (Conti)

• Example
• include ltstdio.hgt
• main()
• struct date
• int month
• int day
• int year
• struct date today
• today.month 9
• today.day 25
• today.year 1988
• printf (Todays date is d/d/d.\n,
  today.month, today.day, today.year )
• Output Todays date is 9/25/1988.