C programming an Introduction

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C programming an Introduction
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Types

• There are only a few basic data types in C.
• char a character
• int an integer, in the range -32,767 to 32,767
• long int a larger integer (up to -2,147,483,647)
  
• float a floating-point number
• double a floating-point number, with more
  precision and perhaps greater range than float

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Declarations

• A declaration tells the compiler the name and
  type of a variable you'll be using in your
  program. In its simplest form, a declaration
  consists of the type, the name of the variable,
  and a terminating semicolon
• EXAMPLES
• char c
• int i
• float f

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Variable names

• Within limits, you can give your variables and
  functions any names you want
• Must be alphanumeric
• Can use underscores etc
• Case in C is significant the variable names
  variable, Variable, and VARIABLE (as well as
  silly combinations like variAble) are all
  distinct.
• A final restriction on names is that you may not
  use keywords (the words such as int and for which
  are part of the syntax of the language) as the
  names of variables or functions (or as
  identifiers of any kind).

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simple output

• Printf
• Examples
• printf("Hello, world!\n")
• \n moves output to a newline
• printf("i is d\n", i)
• In that case, whenever printf printed'' the
  string "i is d", it did not print it verbatim
  it replaced the two characters d with the value
  of the variable i.

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Format specifiers for printf.

• There are quite a number of format specifiers for
  printf. Here are the basic ones
• d print an int argument in decimal
• ld print a long int argument in decimal
• c print a character
• s print a string
• f print a float or double argument
• e same as f, but use exponential notation
• g use e or f, whichever is better
• o print an int argument in octal (base 8)
• x print an int argument in hexadecimal (base 16)
  
• print a single

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Cs backslash codes

• \b backspace
• \f formfeed
• \n newline
• \r carriage return
• \t horizontal tab
• \ double quote
• \0 null
• \\ backslash

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Scanf input operator

• Scanf(formatspecifier,variablename)
• Examples
• scanf(d,a) where a is an integer
• scanf(c,c) where c is a character
• scanf(f,h) where h is a real

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Assignment

• The assignment operator assigns a value to a
  variable. For example,
• x 1 sets x to 1, and
• a b sets a to whatever b's value is.
• The right hand side of an assignment operation
  may be an expression such as
• a a1

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Expression Statements

• Most of the statements in a C program are
  expression statements. An expression statement is
  simply an expression followed by a semicolon. The
  lines
• i 0 i i 1 and printf("Hello, world!\n")
  are all expression statements

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Basic Arithmetic Operators

• Addition
• Subtraction
• Multiplication
• Division /
• Modulus
• Increment
• Decrement --

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Basic program structure

• Include ltstdio.hgt
• main()
• declarations
• statements

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Basic example

• Include ltstdio.hgt
• main()
• int a
• printf(enter number \n)
• scanf(d,a)
• printf(the number you entered is d,a)

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Basic example

• Include ltstdio.hgt
• main()
• int a,b,c
• printf(enter first number \n)
• scanf(d,a)
• printf(enter second number \n)
• scanf(d,b )
• c ab
• printf(the product of the numbers you entered is
  d,c)

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If statements

• The simplest way to modify the control flow of a
  program is with an if statement, which in its
  simplest form looks like this
• if(x gt max) max x
• The syntax of an if statement is
• If ( expression ) statement
• where expression is any expression and statement
  is any statement

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Basic example

• Include ltstdio.hgt
• main()
• int a
• printf(enter number \n)
• scanf(d,a)
• if(a gt 10) printf(the number you entered d is
  more than ten,c)

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A series of statements after an if statement

• What if you have a series of statements, all of
  which should be executed together or not at all
  depending on whether some condition is true? The
  answer is that you enclose them in braces
• if( expression )
• statementltsubgt1lt/subgt
• statementltsubgt2lt/subgt statementltsubgt3lt/subgt

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Basic example

• Include ltstdio.hgt
• main()
• int a,b,c
• printf(enter first number \n)
• scanf(d,a)
• printf(enter second number \n)
• scanf(d,b )
• c ab
• If (c gt 100)
• printf(ok \n)
• printf(the product of the numbers you entered is
  d,c)

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Expressions in If statements

• The expression in an if statement is a Boolean
  expression typically made up of
• Relational and Boolean operators
• The statements in an if stamenst are any legal
  statements

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Relational Operators

• The relational operators such as lt, lt, gt, and gt
  are in fact operators, just like , -, , and /.
• The relational operators take two values, test
  them, and return'' a value of 1 or 0 depending
  on whether the tested relation was true or false.
  
• The complete set of relational operators in C is
  lt less than
• lt less than or equal
• gt greater than
• gt greater than or equal
• equal
• ! not equal For example, 1 lt 2 is 1, 3 gt 4 is
  0, 5 5 is 1, and 6 ! 6 is 0.

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Boolean operators

• The three Boolean operators are
• and
• or
• ! not (takes one operand unary'')

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If else

• if( expression ) statementltsubgt1lt/subgt else
  statementltsubgt2lt/subgt
• if (a gt b) printf(a)
• Else printf(b)

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If else if

• We can also have multiple specific alternatives
  using if else if..
• Suppose we have a variable grade containing a
  student's numeric grade, and we want to print out
  the corresponding letter grade. Here is code that
  would do the job
• if(grade gt 90) printf("A")
• else if(grade gt 80) printf("B")
• else if(grade gt 70) printf("C")
• else if(grade gt 60) printf("D")
• else printf("F")

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Basic example

• Include ltstdio.hgt
• main()
• int a,b,c
• printf(enter first number \n)
• scanf(d,a)
• printf(enter second number \n)
• scanf(d,b )
• If (a gt b !! a gt 5)
• printf(d is greater than d or 5,a,b)
• Else
• printf(d is not greater than d and not greater
  than 5,a,b)