1.History of C Language, Structure of a C program, Statements, Basic Data Types, Variables &Constants, Input & Output statements, Operators and Precedence, Expressions, Simple C programs.

1. Introduction
to
C Programming
•By: Prof. Ganesh Ingle

2. Session objective
History of C Language
Structure of a C program
Statements & Basic Data Types
Variables &Constants
Input & Output statements
Operators, Precedence, Expressions, Simple C programs.
SUMMARY

3. History of C
1960: ALGOL (ALGOrithmic Language)
1967: BCPL (Basic Combined
Programming Language)
1970: B programming language (typeless)
1972: C: BCPL plus B with types
1978: Kernighan + Ritchie standard for C
1989: ANSI standard for C

4. 2.1 Program Structure
4

5. 5
/*-----------------------------------------*/
/* Program chapter1_1 */
/* This program computes the */
/* distance between two points. */
#include <stdio.h>
#include <math.h>
int main(void)
{
/* Declare and initialize variables. */
double x1=1, y1=5, x2=4, y2=7,
side_1, side_2, distance;
/* Compute sides of a right triangle. */
side_1 = x2 - x1;
side_2 = y2 - y1;
distance=sqrt(side_1*side_1 + side_2*side_2);
/* Print distance. */
printf("The distance between the two "
"points is %5.2f n", distance);
return 0; /* Exit program. */
}
/*-----------------------------------------*/
Comments
Preprocessor,
standard C library
every C program must
have main function, this
one takes no parameters
and it returns int value
{  begin
Variable declarations,
initial values (if any)
Statements
must end with ;
indentation
indentation
indentation
return 0
}  end of function

6. Parts of a Program
#include <stdio.h>
int x;
int main () {
int y;
printf("Enter x and y: ");
scanf(&x,&y);
printf("Sum is %dn",x+y);
}
Preprocessor Directive
Global Declaration
Function
Local Declaration
Statements

7. C Program Structure
Preprocessor Directives
Global Declarations
Function Definitions
int main () {
}
Local Declarations
Statements
 Program defined by:
 global declarations
 function definitions
 May contain
preprocessor directives
 Always has one
function named main,
may contain others

8. Outline
II. Program Basics
A. Program skeleton
preprocessor directives
global declarations
functions
local declarations
statements
B. Comments and Documentation
C. Names (identifiers)
reserved words

9. Outline (cont)
II. Program Basics (cont)
D. Variable declarations
1. Memory allocation
2. Atomic types
void, int, float, char
E. Constants
1. literal
2. defined
3. memory

10. Outline (cont)
II. Program Basics (cont)
F. Formatted input/output
1. Files
2. Printf (monitor output)
a. format strings
field specifications
b. data list
3. Scanf (keyboard input)
a. format strings
b. address list
4. Prompting for Input

11. Preprocessor Directives
 Begin with #
 Instruct compiler to perform some
transformation to file before compiling
 Example: #include <stdio.h>
 add the header file stdio.h to this file
 .h for header file
 stdio.h defines useful input/output
functions

12. Declarations
 Global
 visible throughout program
 describes data used throughout program
 Local
 visible within function
 describes data used only in function

13. Functions
 Consists of header and body
 header: int main ()
 body: contained between { and }
 starts with location declarations
 followed by series of statements
 More than one function may be defined
 Functions are called (invoked) - more
later

14. Main Function
 Every program has one function main
 Header for main: int main ()
 Program is the sequence of statements
between the { } following main
 Statements are executed one at a time
from the one immediately following to
main to the one before the }

15. Comments
 Text between /* and */
 Used to “document” the code for the
human reader
 Ignored by compiler (not part of
program)
 Have to be careful
 comments may cover multiple lines
 ends as soon as */ encountered (so no
internal comments - /* An /* internal */

16. Comment Example
#include <stdio.h>
/* This comment covers
* multiple lines
* in the program.
*/
int main () /* The main header */ {
/* No local declarations */
printf(“Too many commentsn”);
} /* end of main */

17. Documentation
 Global - start of program, outlines
overall solution, may include structure
chart
 Module - when using separate files,
indication of what each file solves
 Function - inputs, return values, and
logic used in defining function
 Add documentation for key (tough to
understand) comments
 Names of variables - should be chosen
to be meaningful, make program

18. General Form
18
preprocessing directives
int main(void)
{
declarations
statements
}
 The main function contains
two types of commands:
declarations and statements
 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

19. Another Program
19
/***************************************************/
/* Program chapter1 */
/* This program computes the sum of two numbers */
#include <stdio.h>
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);
system("pause"); /* keep DOS window on the screen*/
return 0; /* Exit program. */
}
/****************************************************/

20. 2.2 Constants and Variables
 What is a variable in math?
f(x) = x2+x+4
 In C,
 A variable is a memory location that holds
a value
 An identifier or variable name is used to
reference a memory location.
20

21. 21
Memory
double x1=1,x2=7,distance;
1 = 00000001
7 = 00000111
? = 01001101
…
11
12
13
14
15
16
…
x1
x2
distance
addressname Memory - content
How many memory cells
does your computer have?
Say it says 2Gbyte memory?
1K=103 or 210 = 1024
1M=106 or 220 = 10242
1G=109 or 230 = 10243

22. Memory Snapshot
22
Name Addr Content
x1 1
y1 5
x2 4
y2 7
side_1 ?
side_2 ?
distance ?

23. Rules for selecting a valid
identifier (variable name)
 Must begin with an alphabetic character or
underscore (e.g., abcABC_)
 May contain only letters, digits and
underscore (no special characters ^%@)
 Case sensitive (AbC, aBc are different)
 Cannot use C keywords as identifiers (e.g.,
if, case, while)
23

24. Are the following valid identifiers?
 distance
 1x
 x_1
24
rate%
x_sum
switch
initial_time
DisTaNce
X&Y

25. C Numeric Data Types
25

26. Example Data-Type Limits
26

27. C Character Data Type: char
27
In memory, everything is stored as binary value, which can be interpreted
as char or integer. Examples of ASCII Codes
char result =‘Y’;

28. 28
Memory
How to represent ‘a’ ?
char My_letter=‘a’;
int My_number = 97
Always we have 1’s and 0’s
in the memory. It depends
on how you look at it?
For example, 01100001 is
97 if you look at it as int, or
‘a’ if you look at it as char
‘3’ is not the same as 3
How to represent 2.5?
‘a’= 01100001
97 = 01100001
? = 01001101
0
1
2
3
4
5
6
…
My_number
addressname Memory - content
My_letter

29. Program to Print Values as
Characters and Integers
29

30. Constants
 A constant is a specific value that we use in our
programs. For example
3.14, 97, ‘a’, or “hello”
 In your program,
int a = 97;
char b =‘a’;
double area, r=2.0;
double circumference;
area = 3.14 * r*r;
circumference = 2 * 3.14 * r;
30
01100001
01100001
?
?
2.0
a
b
area
circumf
erence
r

31. Symbolic Constants
 What if you want to use a better estimate of ?
For example, you want 3.141593 instead of 3.14.
 You need to replace all by hand 
 Better solution, define  as a symbolic constant, e.g.
#define PI 3.141593
…
area = PI * r * r;
circumference = 2 * PI * r;
 Defined with a preprocessor directive
 Compiler replaces each occurrence of the directive
identifier with the constant value in all statements that
follow the directive
31

32. 2.3 Assignment Statements
 Used to assign a value to a variable
 General Form:
identifier = expression;
/* ‘=‘ means assign expression to identifier */
 Example 1
double sum = 0;
 Example 2
int x;
x=5;
 Example 3
char ch;
ch = ‘a’;
32
0
5
‘a’
sum
x
ch

33. Assignment examples (cont’d)
 Example 3
int x, y, z;
x = y = 0;
right to left!
Z = 1+1;
 Example 4
y=z;
y=5;
33
0
0
2
x
y
z
2 5

34. Assignment examples with
different types
int a, b=5;
double c=2.3;
…
a=c; /* data loss */
c=b; /* no data loss */
34
?
5
2.3
a
b
c
2
5.0
long double, double, float, long integer, integer, short integer, char
 Data may be lost. Be careful!
 No data loss

35. Exercise: swap
 Write a set of statements that swaps the
contents of variables x and y
35
3
5
x
y
Before After
5
3
x
y

36. Exercise: swap
First Attempt
x=y;
y=x;
36
Before
3
5
x
y
After x=y
5
5
x
y
After y=x
5
5
x
y

37. Exercise: swap
Solution
temp= x;
x=y;
y=temp;
37
Before
?temp
3
5
x
y
after temp=x after x=y after y = temp
3temp
3
5
x
y
3temp
5
5
x
y
3temp
5
3
x
y
Will the following solution work, too? temp= y;
y=x;
x=temp;
Write a C program to swap the values of two variables

38. 38
OPERATORS
Name Addr Content
Lecture 4

39. Arithmetic Operators
 Addition + sum = num1 + num2;
 Subtraction - age = 2007 – my_birth_year;
 Multiplication * area = side1 * side2;
 Division / avg = total / number;
 Modulus % lastdigit = num % 10;
 Modulus returns remainder of division between two integers
 Example 5%2 returns a value of 1
 Binary vs. Unary operators
 All the above operators are binary (why)
 - is an unary operator, e.g., a = -3 * -4
39

40. Arithmetic Operators (cont’d)
 Note that ‘id = exp‘ means assign
the result of exp to id, so
 X=X+1 means
 first perform X+1 and
 Assign the result to X
 Suppose X is 4, and
 We execute X=X+1
40
4 X5

41. Integer division vs Real division
 Division between two integers results in an
integer.
 The result is truncated, not rounded
 Example:
int A=5/3;  A will have the value of 1
int B=3/6;  B will have the value of 0
 To have floating point values:
double A=5.0/3;  A will have the value of 1.666
double B=3.0/6.0;  B will have the value of 0.5
41

42. Implement a program that computes/prints
simple arithmetic operations
Declare a=2, b=5, c=7, d as int
Declare x=5.0, y=3.0, z=7.0, w as double
d = c%a Print d
d = c/a Print d
w = z/x Print w
d = z/x Print d
w = c/a Print w
a=a+1 Print a
… try other arithmetic operations too.. 42

43. Mixed operations and
Precedence of Arithmetic Operators
43
int a=4+6/3*2;  a=?
int b=(4+6)/3*2;  b=?
a= 4+2*2 = 4+4 = 8
b= 10/3*2 = 3*2= 6
5 assign = Right to left

44. Extend the previous program to compute/print
mixed arithmetic operations
44
Declare a=2, b=5, c=7, d as int
Declare x=5.0, y=3.0, z=7.0, w as double
d = a+c%a Print d
d = b*c/a Print d
w = y*z/x+b Print w
d = z/x/y*a Print d
w = c/(a+c)/b Print w
a=a+1+b/3 Print a
… try other arithmetic operations too..

45. Increment and Decrement Operators
 Increment Operator ++
 post increment x++;
 pre increment ++x;
 Decrement Operator --
 post decrement x--;
 pre decrement --x;
45
} x=x+1;
} x=x-1;
But, the difference is in the following example. Suppose x=10;
A = x++ - 5; means A=x-5; x=x+1; so, A= 5 and x=11
B =++x - 5; means x=x+1; B=x-5; so, B=6 and x=11

46. Abbreviated Assignment Operator
operator example equivalent statement
+= x+=2; x=x+2;
-= x-=2; x=x-2;
*= x*=y; x=x*y;
/= x/=y; x=x/y;
%= x%=y; x=x%y;
!!! x *= 4+2/3  x = x*4+2/3 wrong
x=x*(4+2/3) correct
46

47. Precedence of
Arithmetic Operators (updated)
47

48. Writing a C statement for a
given MATH formula
 Area of trapezoid
area = base*(height1 + height2)/2;
 How about this
48
2
)(* 21 heightheightbase
area


g
mm
mm
Tension 


21
212

49. 49
Exercise
 Write a C statement to compute the following
14.305.0
3.62
2
23



xx
xxx
f
f = (x*x*x-2*x*x+x-6.3)/(x*x+0.05*x+3.14);
Tension = 2*m1*m2 / m1 + m2 * g;
Tension = 2*m1*m2 / (m1 + m2) * g
wrong
g
mm
mm
Tension 


21
212

50. Exercise: Arithmetic operations
 Show the memory snapshot after the
following operations by hand
int a, b, c=5;
double x, y;
a = c * 2.5;
b = a % c * 2 - 1;
x = (5 + c) * 2.5;
y = x – (-3 * a) / 2;
Write a C program and print out the
values of a, b, c, x, y and compare them
with the ones that you determined by
hand.
50
?
?
5
?
?
a
b
c
x
y
a = 12 b = 3 c= 5 x = 25.0000 y = 43.0000

51. Exercise: Arithmetic
operations
 Show how C will perform the following
statements and what will be the final
output?
int a = 6, b = -3, c = 2;
c= a - b * (a + c * 2) + a / 2 * b;
printf("Value of c = %d n", c);
51

52. Step-by-step show how C will
perform the operations
c = 6 - -3 * (6 + 2 * 2) + 6 / 2 * -3;
c = 6 - -3 * (6 + 4) + 3 * -3
c = 6 - -3 *10 + -9
c = 6 - -30 + -9
c = 36 + -9
c = 27
 output:
Value of c = 27
52

53. Step-by-step show how C will
perform the operations
int a = 8, b = 10, c = 4;
c = a % 5 / 2 + -b / (3 – c) * 4 + a / 2 * b;
printf("New value of c is %d n", c);
53

54. Exercise: reverse a number
 Suppose you are given a number in the
range [100 999]
 Write a program to reverse it
 For example,
num is 258
reverse is 852
54
int d1, d2, d3, num=258, reverse;
d1 = num / 100;
d2 = num % 100 / 10;
d3 = num % 10;
reverse = d3*100 + d2*10 + d1;
printf(“reverse is %dn”, reverse);
d1 = num / 100;
d3 = num % 10;
reverse = num – (d1*100+d3) +
d3*100 + d1;

55. 55
Lecture++;
Name Addr Content
Lecture 5

56. 2.4 Standard Input and Output
 Output: printf
 Input: scanf
 Remember the program computing the distance between
two points!
 /* Declare and initialize variables. */
 double x1=1, y1=5, x2=4, y2=7,
 side_1, side_2, distance;
 How can we compute distance for different points?
 It would be better to get new points from user, right? For
this we will use scanf
 To use these functions, we need to use
#include <stdio.h>
56

57. Standard Output
 printf Function
 prints information to the screen
 requires two arguments
 control string
 Contains text, conversion specifiers or both
 Identifier to be printed
 Example
double angle = 45.5;
printf(“Angle = %.2f degrees n”, angle);
Output:
Angle = 45.50 degrees
57
Control String
Identifier
Conversion
Specifier

58. 58
Conversion Specifiers for
Output Statements
Frequently Used

59. Standard Output
Output of -145 Output of 157.8926
Specifier Value Printed
%f 157.892600
%6.2f 157.89
%7.3f 157.893
%7.4f 157.8926
%7.5f 157.89260
%e 1.578926e+02
%.3E 1.579E+02
59
Specifier Value Printed
%i -145
%4d -145
%3i -145
%6i __-145
%-6i -145__
%8i ____-145
%-8i -145____

60. 60
Exercise
printf("Sum = %5i; Average = %7.1f n", sum, average);
printf("Sum = %4i n Average = %8.4f n", sum, average);
printf("Sum and Average nn %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);
int sum = 65;
double average = 12.368;
char ch = ‘b’;
Show the output line (or lines) generated by the following statements.

61. 61
Exercise (cont’d)
 Solution
Sum = 65; Average = 12.4
Sum = 65
Average = 12.3680
Sum and Average
65 12.4
Character is b; Sum is A
Character is 98; Sum is 65

62. 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("%lf %c", &distance, &unit_length);
 It is very important to use a specifier that is appropriate for the data
type of the variable
62

63. 63
Conversion Specifiers for
Input Statements
Frequently Used

64. 64
Exercise
float f;
int i;
scanf(“%f %i“, &f, &i);
 What will be the values stored in f and i after scanf statement if
following values are entered
12.5 1
12 45
12 23.2
12.1 10
12
1

65. Good practice
 You don’t need to have a printf before
scanf, but it is good to let user know what
to enter:
printf(“Enter x y : ”);
scanf(“%d %d”, &x, &y);
 Otherwise, user will not know what to do!
 What will happen if you forget & before
the variable name?
65

66. Exercise: How to input two points
without re-compiling the program
66
printf(“enter x1 y1: “);
scanf(“%lf %lf“, &x1, &y1);
printf(“enter x2 y2: “);
scanf(“%lf %lf“, &x2, &y2);

67. Programming exercise
 Write a program that asks user to enter
values for the double variables (a, b, c, d)
in the following formula. It then computes
the result (res) and prints it with three
digits after .
67
ca
bc
ba
ca
dc
ba
res









68. Exercise
 Study Section 2.5 and 2.6 from the
textbook
68

69. 69
Lecture++;
Name Addr Content
Lecture 6

70. Library Functions
70

71. 2.7 Math Functions
71
#include <math.h>
fabs(x) Absolute value of x.
sqrt(x) Square root of x, where x>=0.
pow(x,y) Exponentiation, xy. Errors occur if
x=0 and y<=0, or if x<0 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 x<=0.
log10(x) Returns log10x, logarithm of x to the base 10.
Errors occur if x<=0.

72. Trigonometric Functions
72
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 [-, ].

73. Parameters or Arguments of a
function
 A function may contain no argument or contain one
or more arguments
 If more than one argument, list the arguments in the
correct order
 Be careful about the meaning of an argument. For
example, sin(x) assumes that x is given in radians, so
to compute the sin of 60 degree, you need to first
conver 60 degree into radian then call sin function:
#define PI 3.141593
theta = 60;
theta_rad = theata * PI / 180;
b = sin(theta_rad); /* is not the same as sin(theta); */
73

74. Exercise
 Write an expression to compute velocity using the following
equation
 Assume that the variables are declared
)(22
xoxavovelocity 
74
velocity = sqrt(vo*vo+2*a*(x-xo));
velocity = sqrt(pow(vo,2)+2*a*(x-xo));

75. Exercise
 Write an expression to compute velocity using the following
equation
 Assume that the variables are declared
asr
asr
center
)(
sin)(19.38
22
33



75
center = (38.19*(pow(r,3)-pow(s,3))*sin(a))/
((pow(r,2)-pow(s,2))*a);
Make sure that a is given in radian; otherwise, first convert it to radian
center = (38.19*(r*r*r - s*s*s)*sin(a))/((r*r –s*s)*a);

76. Exercise: Compute Volume
 Write a program to compute the volume
of a cylinder of radius r and height h
hrV 2

76
h
r

77. Solution: Compute Volume
77
Problem Solving Methodology
1. Problem Statement
2. Input/Output Description
3. Hand Example
4. Algorithm Development
5. Testing

78. Solution: Compute Volume
(cont’d)
 Problem Statement
 compute the volume of a cylinder of radius r and
height h
 Input Output Description
78
radius r
height h
volume v

79. Solution: Compute Volume
(cont’d)
 Hand example
 r=2, h =3, v=37.68
 Algorithm Development
 Read radius
 Read height
 Compute Volume
 Print volume
 Convert to a program (see next slide)
79
hrV 2


80. Solution: Compute Volume
(coding)
80
#include <stdio.h>
#define PI 3.141593
int main(void)
{
/* Declare Variables */
double radius, height, volume;
printf("Enter radius: "); scanf("%lf",&radius);
printf("Enter height: "); scanf("%lf",&height);
/* Compute Volune */
volume = PI*radius*radius*height;
/* Print volume */
printf("Volume = %8.3f n", volume);
system("pause");
exit(0);
}

81. 81
Exercise
 Write a program to find the radius of a circle
given its area. Read area from user. Compute
radius and display it.
2
rA 
r

82. Exercise
C
c
B
b
A
a
sinsinsin

82
AbcBacCabarea sin
2
1
sin
2
1
sin
2
1

A
B Ca
b
c
Write a program that asks user to
enter A in degrees, a and b in cm,
then computes
B=? in degrees
C=? in degrees
c=? in cm
area=? in cm2
For example, given A=36o, a=8 cm, b=5 cm:
B=21.55o, C=122.45o, c=11.49 cm

83. Write a program that finds the
intersection of two lines and the
angle between them
 See handout
83

84. 2.8 Character Functions
84
#include <ctype.h>
putchar(‘a’);
C= getchar();
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.

85. Exercise
85
What is the output of the following program
#include <stdio.h>
#include <ctype.h>
int main(void)
{
char ch1='a', ch2;
char ch3='X', ch4;
char ch5='8';
ch2 = toupper(ch1);
printf("%c %c n",ch1,ch2);
ch4 = tolower(ch3);
printf("%c %c n",ch3,ch4);
printf("%dn",isdigit(ch5));
printf("%dn",islower(ch1));
printf("%dn",isalpha(ch5));
system("pause");
return(0);
}

86. Skip
 Study Section 2.9 from the textbook
 Skip Section 2.10
86