Engineering Problem Solving with C Fundamental Concepts

1
Engineering Problem Solving with C Fundamental
Concepts

• Chapter 2
• Simple C Programs

2
Overview

1. Program Structure
2. Constants and Variables
3. Assignment Statement
4. Standard Input and Output
5. Mathematical Function
6. Character Function

3
Program Structure
4
Program Structure - General Form

• preprocessing directives
• int main(void)
• declarations
• statements

include ltstdio.hgt
eg
include ltmath.hgt
5
Program Structure

• Comments begin with the characters / and end
  with the characters /
• Preprocessor directives give instructions to the
  compiler. Provides instructions that are
  performed before the program is compiled.
• stdioh.h file contains info related to the o/p
  statement used in the program.
• math.h file contain info related to the
  function used in the program to compute a
  mathematical function (egsquare root).

6
Program Structure - continued

• Every C program contains one function named main.
• Int indicates the function returns an integer
  value to the OS.
• Void indicates the function is not receiving any
  info from OS.
• The body of the main function is enclosed by
  braces,

7
Program Structure - continued

• The main function contains two types of commands
  declarations and statements.
• Declaration define the memory locations that
  will be used by the statements.
• It may or may not give initial values to be
  stored.
• Declarations and statements are required to end
  with a semicolon ()
• Preprocessor directives do not end with a
  semicolon
• To exit the program, use a return 0 statement

8
Header Files

• Information about the functions can be supplied
  to the program by using header files
• The files have a .h extension
• The header file is added to the program using the
  include preprocessor directive
• The include directive tells the compiler to read
  in another file and include it in your program
• The most common header file is stdio.h

9
Components of the Lesson
include ltstdio.hgt void main(void)
printf(This is C!)
10
Program Structure - First Program

• /
  /
• / Program chapter1 /
• /
  /
• / This program computes the sum two numbers /
• include ltstdio.hgt
• int main(void)
• / Declare and initialize variables. /
• double number1 473.91, number2 45.7, sum
• / Calculate sum. /
• sum number1 number2
• / Print the sum. /
• printf(The sum is 5.2f \n, sum)
• / Exit program. /
• return 0

11
Constants and Variables
12
Constants and Variables

• A constant is a specific value
• A variable is a memory location that is assigned
  a name or an identifier
• An identifier is used to reference a memory
  location.
• Rules for selecting a valid identifier
• must begin with an alphabetic character or
  underscore
• may contain only letters, digits and underscore
  (no special characters)
• case sensitive thus uppercase letters are
  different from lower case letter.
• cannot use keywords as identifiers (pg 38, table
  2.1). This is because keywords have special
  meaning to the C compiler.

13
Keywords
14
Practice!
15
C Data Types

• Integers
• short
• int
• long
• Floating-Point Values
• float
• double
• long double
• Characters
• char

16

• short maximum 32767
• int maximum 2147483647
• long maximum 2147483647
• float precision digits 6
• float maximum exponent 38
• float maximum 3.402823e038
• double precision digits 15
• double maximum exponent 308
• double maximum 1.797693e308
• long double precision 15
• long double maximum exponent 308
• long double maximum 1.797693e308

17
Symbolic Constants

• Defined with a preprocessor directive that
  assigns an identifier to the constant.
• Compiler replaces each occurrence of the
  directive identifier with the constant value in
  all statements that follow the directive
• Example
• define PI 3.141593

18
Example
include ltstdio.hgt define DAYS_IN_YEAR
365 define PI 3.14159 void mail()
statement
19
Practice!

• Give the preprocessor directives to assign
  symbolic constants for these
• constants
• 1. Speed of light,c 2.99792 X 108 m/s
• 2. Charge of an electron, e 1.602177 X 10-19 C
• Avogadros number, NA 6.022 X 1023 mol-1
• Accelaration of gravity, g 9.8 m/s2
• Unit of length, Unit_length m
• Unit of time, Unit_Time s

20
Assignment Statements
21
Assignment Statements

• Used to assign a value to a variable/identifier.
• General Form
• identifier expression
• Example 1
• double sum 0 sum
• Example 2
• int x
• x5 x
• Example 3
• char ch
• ch a ch

0
5
a
22
Assignment Statements - continued

• Example 3
• int x, y, z
• xy0
• z2 x
• y
• z
• Example 4
• yz y

0
0
2
2
23
Arithmetic Operators

• Addition
• Subtraction -
• Multiplication
• Division /
• Modulus
• Modulus returns remainder of division between two
  integers
• Example
• 52 returns a value of 1

24
Mixed Operation

• Operation between values with different types
• Before operation the value with the lower type is
  converted or promoted to the higher type
• eg
• Cast operator specify the type change in the
  value before the next compuation
• eg int sum, count
• float average
• average (float)sum/count

float
converted
int
float
float
float
25
Integer Division

• Division between two integers results in an
  integer.
• The result is truncated, not rounded
• Example
• 5/3 is equal to 1
• 3/6 is equal to 0

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Priority of Operators

• Parentheses Inner most first
• Unary operators Right to left
• ( -)
• Binary operators Left to right
• ( / )
• Binary operators Left to right
• ( -)

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Increment and Decrement Operators

• Increment Operator
• post increment x
• pre increment x
• Decrement Operator - -
• post decrement x- -
• pre decrement - -x

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Increment and Decrement Operators

• If the increment/decrement operator is in prefix
  position,the identifier is modified and the new
  value is used to evaluate the rest of the
  expression.
• If the increment/decrement operator is in postfix
  position, the old value of the identifier is
  used to evaluate the rest of the expression and
  then the identifier is modified.

29
Example
include ltstdio.hgt void main(void) int i 1, j
1, k , h printf(Before increment i d,
jd, i, j) k i h j
printf(After increment i d, jd, kd,
hd,i ,j , k, h)
30
Practice!

• For the following statements find the values
• generated for p and q?
• int p 0, q 1
• p q
• p q
• p q--
• p --q

31
Practice

• Assume
• int counter4, a5, b-7, c
• And the arithmetic expression statement
• c a counter - b
• Answer
• counter ? , c ?

32
Abbreviated Assignment Operator

• operator example equivalent statement
• x2 xx2
• - x-2 xx-2
• xy xxy
• / x/y xx/y
• xy xxy

33
Abbreviated Assignment Operator

• C allows simple assignment statements to be
  abbreviated.
• xx3 ? x 3
• sumsum x ? sum x
• dd/4.5 ? d / 4.5
• rr2 ? r 2

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35
Practice!

• Give a memory snapshot after each statement is
  executed, assuming that x is equal to 2 and that
  y is equal to 4 before the statement is executed.
  Also, assume that all the variables are integers.
• zxy
• zxy
• xy
• yx

36
Standard Input and Output
37
Standard Output

• printf Function
• prints information to the screen
• requires two arguments
• control string
• conversion specifier
• Example
• double angle 45.5
• printf(Angle .2f degrees \n, angle)
• Output
• Angle 45.50 degrees

Control string
Conversion specifier
38
Standard Input

• scanf Function
• inputs values from the keyboard
• required arguments
• control string
• memory locations that correspond to the
  specifiers in the control string
• Example
• double distance
• char unit_length
• scanf("1f c", distance, unit_length)
• It is very important to use a specifier that is
  appropriate for the data type of the variable

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40
Practice!

• Assume that the integer variable sum contains the
  value 65, the double variable average contains
  the value 12.368 and that the char variable ch
  contains the value 'b'. Show the output line
  (or lines) generated by the following statements.
• printf("Sum 5i Average 7.1f \n", sum,
  average)
• printf("Sum 4i \n Average 8.4f \n", sum,
  average)
• printf("Sum and Average \n\n d .1f \n", sum,
  average)
• printf("Character is c Sum is c \n", ch, sum)
• printf("Character is i Sum is i \n", ch, sum)

41
Practice!

• Write a program to convert from Fahrenheit to
  Celsius values. The program should prompt the
  user for Fahrenheit value and then accept the
  user input (a floating point value). After the
  input is read into a variable (called fahr),
  convert the Fahrenheit value according to
• celsius (5.0 / 9.0) (fahr 32.0)
• In the above program, change the expression (5.0
  / 9.0) to (5 / 9), recompile and run the program,
  and study the output. Why is the answer wrong?

42
Library Functions
43
Library functions

• The library functions are important component of
  C programs
• The ANSI C standard specifies a minimum set of
  library functions to be supplied by all compilers
• This is called the C standard library
• The standard library contains functions to
  perform disk I/O, string manipulation etc.
• The code for the library functions is added to
  the program at link time
• Using functions for I/O increases flexibility

44
Math Functions

• fabs(x) Absolute value of x.
• sqrt(x) Square root of x, where xgt0.
• pow(x,y) Exponentiation, xy. Errors occur if
• x0 and ylt0, or if xlt0 and y is not an
  integer.
• ceil(x) Rounds x to the nearest integer toward ?
  (infinity).
• Example, ceil(2.01) is equal to 3.
• floor(x) Rounds x to the nearest integer toward
  -? (negative infinity). Example, floor(2.01)
  is equal to 2.
• exp(x) Computes the value of ex.
• log(x) Returns ln x, the natural logarithm of x
  to the base e. Errors occur if xlt0.
• log10(x) Returns log10x, logarithm of x to the
  base 10.
• Errors occur if xlt0.

45
Trigonometric Functions

• sin(x) Computes the sine of x, where x is in
  radians.
• cos(x) Computes the cosine of x, where x is in
  radians
• tan(x) Computes the tangent of x, where x is in
  radians.
• asin(x) Computes the arcsine or inverse sine of
  x,
• where x must be in the range -1, 1.
• Returns an angle in radians in the range
  -?/2,?/2.
• acos(x) Computes the arccosine or inverse cosine
  of x,
• where x must be in the range -1, 1.
• Returns an angle in radians in the range 0,
  ?.
• atan(x) Computes the arctangent or inverse
  tangent of x. The Returns an angle in radians
  in the range -?/2,?/2.
• atan2(y,x) Computes the arctangent or inverse
  tangent of the value y/x. Returns an angle in
  radians in the range -?, ?.

46
Character Functions

• toupper(ch) If ch is a lowercase letter, this
  function returns the corresponding uppercase
  letter otherwise, it returns ch
• isdigit(ch) Returns a nonzero value if ch is a
  decimal digit otherwise, it returns a zero.
• islower(ch) Returns a nonzero value if ch is a
  lowercase letter otherwise, it returns a
  zero.
• isupper(ch) Returns a nonzero value if ch is an
  uppercase letter otherwise, it returns a
  zero.
• isalpha(ch) Returns a nonzero value if ch is an
  uppercase letter or a lowercase letter
  otherwise, it returns a zero.
• isalnum(ch) Returns a nonzero value if ch is an
  alphabetic character or a numeric digit
  otherwise, it returns a zero.