1. Fundamental of Programming (C)
Lecture 3
Constants, Variables, Data Types, And Operations

2. Outline C Program Data types Variables Constants Operations
Arithmetic Operators
unary operators
operators that require only one operand
binary operators
operators that require two operands
Assignment Operators
Equality and Relational Operators
Logical Operators
Bitwise Operators
Conditional Operator
Comma Operator
sizeof

3. C Program Constants and variables main stdout (Screen) A B C D
stderr (Screen)
stdin (Keyboard)
Instructions and operating procedures X Y Z
Operations and functions

4. Simple Program Examples: // int is return data type
// main is entrance function
int main() {
statement 1;
// ….
return 0; }
// Simplest c program
int main() {
return 0; } /*
Objective: print on screen */
#include <stdio.h> // preprocessor statements have not ;
int main() {
printf("welcome to c!!!");
return 0; // indicate that program ended successfully }
welcome to c!!!

5. Examples: #include <stdio.h> // header file (preprocessor )
// calculating sum of two user input variables
int main() {
/* variable definition */
int a;
int b;
int result = 0;
// get first variables form user
printf("Enter first number:\n");
scanf("%d", &a);
// get scoend variables form user
printf("Enter scoend number:\n");
scanf("%d", &b);
// sum of input variables
result = a + b;
printf("%d + %d = %d\n", a, b, result);
system("Pause");
return 0; }
Examples:
Header file
Main function
Variables
Input and output
Process

6. Examples: #include <stdio.h> // (preprocessor )
#define PI // PI constant (preprocessor )
// calculating area of circle
int main() {
/* variable definition */
float Radius;
float Area = 0;
// get radius of circle form user
printf("Enter Radius :\n");
scanf("%f", &float );
// calculating area of circle
Area = PI * Radius * Radius;
printf(“Area = %f", Area );
system("Pause");
return 0; }
Examples:
Header file
Constant
Main function
Variables
Input and output
Process

7. Examples: #include <stdio.h> // (preprocessor )
#define PI // PI constant (preprocessor )
// calculating area of circle
int main() {
/* variable definition */
float Radius;
float Area = 0;
// get radius of circle form user
printf("Enter Radius :\n");
scanf("%f", & Radius);
// calculating area of circle
Area = PI * Radius * Radius;
printf(“Area = %f", Area );
system("Pause");
return 0; }
Examples:
Header file
Constant
Main function
Variables
Input and output
Process

8. Variables Have the same meaning as variables in algebra
Single alphabetic character
Each variable needs an identifier that distinguishes it from the others
a = 5
x = a + b
valid identifier in C may be given representations containing multiple characters
A-Z, a-z, 0-9, and _ (underscore character)
First character must be a letter or underscore (no, _no 9no)
Usually only the first 32 characters are significant
There can be no embedded blanks (student no)
Identifiers are case sensitive (area, Area, AREA, ArEa)
Keywords cannot be used as identifiers

9. Reserved Words (Keywords) in C
auto
break
int
long
case
char
register
return
const
continue
short
signed
default do
sizeof
static
double
else
struct
switch
enum
extern
typedef
union
float
for
unsigned
void
goto if
volatile
while

10. Naming Conventions
C programmers generally agree on the following conventions for identifier:
Use meaningful identifiers
Separate words within identifiers with:
underscores
capitalize each word
Examples:
surfaceArea
SurfaceArea
Surface_Area

11. Variable declaration Before using a variable, you must declare it
Data_Type Identifier;
int width; // width of rectangle
float area; // result of calculating area stored in it
char separator; // word separator
Data_Type Identifier = Initial_Value;
int width = 10; // width of rectangle
float area = 255; // result of calculating area stored in it
char seperator = ‘,’; // word separator
Data_Type Identifier, Identifier, Identifier ,….;
int width, length, temporary;
float radius, area = 0;

12. Variable declaration When we declare a variable
Space is set aside in memory to hold a value of the specified data type
That space is associated with the variable name
That space is associated with a unique address
Visualization of the declaration
int width = 95; // get width form user
// &width is 22ff40
// *&width is 95
// sizeof width is 4
& *
address
data
22ff40 95
22ff44

13. Data types Minimal set of basic data types
primitive data types
int
float
double
char
Void
The size and range of these data types may vary among processor types and compilers

14. Data type qualifiers
Modify the behavior of data type to which they are applied:
Size qualifiers: alter the size of the basic data types:
short: multiply by 0.5
long: multiply by 2
short can be applied to: int
long can be applied to: int and double
Sign qualifiers: can hold both positive and negative numbers, or only positive numbers.:
signed: + and -
unsigned: +
they can be applied to : int and char

15. Data type size and range
Example
Qualifier
Data type 8
signed char c;
unsigned char c;
char c;
signed
unsigned
char
signed (16):
unsigned (16):
signed (32):
unsigned (32): 16
16 or 32 32 64
signed short i; signed short int i;
unsigned int i;
int i;
signed int i;
short i; short int i;
long i; long int i; signed long i; signed long int i;
long long i; long long int i; signed long long i; signed long long int i;
short
long
int
+/- 3.4e +/- 38 (~7 digits)
float f;
float
+/- 1.7e +/- 308 (~15 digits) 80
double d;
long double d;
double

16. Overflow and Underflow
/* The # character indicate a pre-processor directive; it's an instruction to the compiler to make it do something The <> character tell C to look in the system area for the file stdio.h. If I had given the name #include "stdio.h" instead it would tell the compiler to look in the current directory #include <stdio.h> * Function main begins program execution * Semi-colon is statement terminator, so it is as a signal to the compiler for end of line */ int main() { /* The 2 curly brackets { }, are used to specify the limits of the program block */ char letter = 'A'; // char variable to show ASCII code short shortVariable = 32769; // short variable for test overflow // printf command display string on the monitor printf("current value of shortVariable is = %d\n", shortVariable); printf("current value of letter is = %d", letter); printf("current value of letter is = %c", letter); system("PAUSE"); // pause the execution to show press any key … return 0; // indicate that program ended successfully }
current value of shortVariable is =
current value of letter is = 65
current value of letter is = A

17. Program Error Compile-time or syntax Run-time Logical
is caused when the compiler cannot recognize a statement
Run-time
E.g. division by zero
Logical
E.g. Overflow and Underflow

18. Examples: #include <stdio.h> // (preprocessor )
#define PI // PI constant (preprocessor )
// calculating area of circle
int main() {
/* variable definition */
float Radius;
float Area = 0;
// get radius of circle form user
printf("Enter Radius :\n");
scanf("%f", &float );
// calculating area of circle
Area = PI * Radius * Radius;
printf(“Area = %f", Area );
system("Pause");
return 0; }
Examples:
Header file
Constant
Main function
Variables
Input and output
Process

19. Integer constant value
Base 10:
Base 8:
Base 16: 0x1 0X5 0x7fab
unsigned: 5000u 4U
long: l 56L
unsigned long: ul
long long : LL 25lL
Example :
0xABu uL 017LL

20. floating-point constant value
A floating-point value contains a decimal point
For example, the value is represented in scientific notation as
X 102
and is represented in exponential notation (by the computer) as
E+02
This notation indicates that is multiplied by 10 raised to the second power (E+02)
The E stands for “exponent”

21. Char and string constant value
char c;
c = 'A'; // d = 65;
String
printf("string is array of char!!!");
printf("example of escape sequence is \n");

22. Constant
Constants provide a way to define a variable which cannot be modified by any other part in the code
#define: without memory consume
const: memory consume
#define Identifier constant_value
#define PI
#define ERROR "Disk error "
#define ERROR "multiline \
message"
#define ONE 1
#define TWO ONE + ONE

23. Constant const [Data_Type] Identifier = constant_value;
const p = 3; // const int p = 3;
const p;
p = 3.14; // compile error
const p = 3.14; // p = 3 because default is int
const float p = 3.14;

24. Examples: #include <stdio.h> // (preprocessor )
#define PI // PI constant (preprocessor )
// calculating area of circle
int main() {
/* variable definition */
float Radius;
float Area = 0;
// get radius of circle form user
printf("Enter Radius :\n");
scanf("%f", &float );
// calculating area of circle
Area = PI * Radius * Radius;
printf(“Area = %f", Area );
system("Pause");
return 0; }
Examples:
Header file
Constant
Main function
Variables
Input and output
Process

25. Operators Arithmetic Operators Assignment Operators
unary operators
operators that require only one operand
binary operators
operators that require two operands
Assignment Operators
Equality and Relational Operators
Logical Operators
Bitwise Operators
Conditional Operator
Comma Operator
sizeof
Width * High
Operand

26. Arithmetic Operators Unary Operator C operation Operator Expression
Explanation
Positive +
a = +3;
Negative -
b = -4;
Increment ++
i++;
Equivalent to i = i + 1
Decrement
- -
i - -;
Equivalent to i = i - 1

27. PRE / POST Increment Consider this example: But if we have:
int width = 9;
printf("%d\n", width);
width++;
int width = 9;
printf("%d\n", width++);
printf("%d\n", width); 9 10
int width = 9;
width++;
printf("%d\n", width);
int width = 9;
printf("%d\n", ++width);
printf("%d\n", width); 10

28. Equivalent Statements
PRE / POST Increment
int R = 10;
int count = 10;
++ Or -- Statement
Equivalent Statements R
count
R = count++;
R = count;
count = count + 1; 10 11
R = ++count;
R = count--;
count = count – 1; 9
R = --count;

29. Arithmetic Operators Binary Operators C operation Operator Expression
Addition +
b = a + 3;
Subtraction -
b = a – 4;
Multiplication *
b = a * 3;
Division /
b = a / c;
Modulus (integer) %
b = a % c;

30. Division
The division of variables of type integer will always produce a variable of type integer as the result
Example
int a = 7, b;
float z;
b = a / 2;
z = a / 2.0;
printf("b = %d, z = %f\n", b, z);
Since b is declared as an integer, the result of a/2 is 3, not 3.5
b = 3, z =

31. Modulus
You could only use modulus (%) operation on integer variables (int, long, char)
z = a % 2.0; // error
z = a % 0; // error
Example
int a = 7, b, c;
b = a % 2;
c = a / 2;
printf("b = %d\n", b);
printf("c = %d\n", c);
Modulus will result in the remainder of a/2. 7 2 6 3 1 -
a/2
integral
a%2
remainder

32. Assignment Operators lvalue = rvalue; int i; float f;
i = 2; // *&i = 2;
2 = i; // error: invalid lvalue in assignment
f = 5.6;
i = f; // i = 5;
i = -5.9; // i = -5;

33. Assignment Operators
Assignment operators are used to combine the '=' operator with one of the binary arithmetic or bitwise operators
Example :
c = 9;
Operator
Expression
Equivalent Statement
Results +=
c += 7;
c = c + 7;
c = 16 -=
c -= 8;
c = c – 8;
c = 1 *=
c *= 10;
c = c * 10;
c = 90 /=
c /= 5;
c = c / 5; %=
c %= 5;
c = c % 5;
c = 4
&=
c &= 2 ;
c = c & 2;
c = 0 ^=
c ^= 2;
c = c ^ 2;
c = 11 |=
c |= 2;
c = c | 2;
<<=
c <<= 2;
c = c << 2;
c = 36
>>=
c >>= 2;
c = c >> 2;
c = 2

34. Precedence Rules
The rules specify which of the operators will be evaluated first
For example: x = 3 * a - ++b%3;
Precedence
Operator
Associativity Level
1 (highest) ()
left to right 2
unary
right to left 3
* / % 4
+ -
5 (lowest)
= += -= *= /= %=
c = b = d = 5;

35. Precedence Rules how would this statement be evaluated?
: x = 3 * a - ++b % 3;
What is the value for X, for: a = 2, b = 4?
x = 3 * a - ++b % 3;
x = 3 * a % 3;
x = 3 * a - 5 % 3;
x = % 3;
x = 6 – 2;
x = 4;

36. Precedence Rules
If we intend to have a statement evaluated differently from the way specified by the precedence rules, we need to specify it using parentheses ( )
x = 3 * a - ++b % 3;
Consider having the following statement:
x = 3 * ((a - ++b)%3);
the expression inside a parentheses will be evaluated first
The inner parentheses will be evaluated earlier compared to the outer parentheses

37. Precedence Rules how would this statement be evaluated?
x = 3 * ((a - ++b)%3);
What is the value for X, for: a = 2, b = 4?
x = 3 * ((a - ++b) % 3);
x = 3 * ((a - 5) % 3);
x = 3 * ((-3) % 3);
x = 3 * 0;
x = 0;

38. Precedence Rules how would this statement be evaluated?
x = 3 * ++a – b--%3;
What is the value for X, for: a = 2, b = 4?
x = 3 * ++a – b-- % 3;
x = 3 * ++a – 4 % 3;
x = 3 * 3 – 4 % 3;
x = 9 – 1;
x = 8;
b = b -1 , b = 3;

39. Equality and Relational Operators
Equality Operators:
Relational Operators:
Operator
Example
Meaning ==
x == y
x is equal to y !=
x != y
x is not equal to y
Operator
Example
Meaning
>
x > y
x is greater than y
<
x < y
x is less than y
>=
x >= y
x is greater than or equal to y
<=
x <= y
x is less than or equal to y

40. Logical Operators
Logical operators are useful when we want to test multiple conditions
AND OR
NOT
C has not bool data type, but:
0: evaluate to false
If(0) printf(" …");
other: evaluate to true
If(1) printf(" …");
If(-13) printf(" …");

41. && - Logical AND
All the conditions must be true for the whole expression to be true
Example: if (a == 1 && b == 2 && c == 3)
means that the if statement is only true when a == 1 and b == 2 and c == 3
If (a = 5) … e1 e2
Result = e1 && e2 1 e1 e2
Result = e1 && e2
false
true

42. || - Logical OR
The truth of one condition is enough to make the whole expression true
Example: if (a == 1 || b == 2|| c == 3)
means the if statement is true when either one of a, b or c has the right value e1 e2
Result = e1 || e2 1 e1 e2
Result = e1 || e2
false
true

43. ! - Logical NOT Reverse the meaning of a condition
Example: if (!(radius > 90))
Means if radius not bigger than 90. e1
Result = !e1 1 e1
Result = !e1
false
true

44. Bitwise Operators Apply to all kinds of int and char types:
signed and unsigned
char, short, int, long, long long
Operator
Name
Description
&
AND
Result is 1 if both operand bits are 1 | OR
Result is 1 if either operand bit is 1 ^
XOR
Result is 1 if operand bits are different ~
Not (Ones Complement)
Each bit is reversed
<< 
Left Shift
Multiply by 2
>> 
Right Shift
Divide by 2

45. Bitwise Operators Applicable for low level programming, e.g.: Usually:
Port manipulation
I/O programming
Usually:
&: set OFF one bit
|: set ON one bit
^: reverse one bit

46. XOR e1 e2
Result = e1 ^ e2 1

47. Examples A = 199; B = 90; c = a & b = 66; c = a | b = 233;1 1 1 1 1 1 1

48. Conditional Operator
The conditional operator (?:) is used to simplify an if/else statement
Condition ? Expression1 : Expression2;
The statement above is equivalent to:
if (Condition)
Expression1;
else
Expression2;
Which are more readable?

49. Conditional Operator Example: if/else statement:
if (total > 12)
grade = ‘P’;
else
grade = ‘F’;
conditional statement:
(total > 12) ? grade = ‘P’: grade = ‘F’; OR
grade =( total > 12) ? ‘P’: ‘F’;

50. Conditional Operator Example: if/else statement: if (total > 12)
printf(“Passed!!\n”);
else
printf(“Failed!!\n”);
Conditional Statement:
printf(“%s!!\n”, total > 12 ? “Passed”: “Failed”);

51. Comma Operator (Expression1 ,Expression2,…); Example: int x, y, z;
z = (x = 2, y = x + 1);
printf("z = %d", z);
int x, y, z;
x = 2;
y = x + 1;
z = y;
printf("z = %d", z);

52. sizeof
The sizeof keyword returns the number of bytes of the given expression or type
returns an unsigned integer result
sizeof variable_Identifier;
sizeof (variable_Identifier);
sizeof (Data_Taype);
Example:
int x;
printf("size of x = %d", sizeof x);
printf("size of long long = %d", sizeof(long long));
printf("size of x = %d", sizeof (x));

53. Type Casting
Explicit Type cast: carried out by programmer using casting
int k, i = 7;
float f = 10.14;
char c = 'B';
k = (i + f) % 3; // error
k = (int)(i + f) % 3;
Implicit Type cast: carried out by compiler automatically
f = 65.6;
i = f; //f = (int)f;
c = i; // c = (int)i;

54. Type Casting char c = 'A'; short s = 1; int i; float f; double d;
i = (c s);
(int) (char) (short)
(short)
(int)
d = (c / i) (f * d) (f i);
(char) (int) (float) (double) (float) (int)
int double float
double

55. Precedence Rules Primary Expression Operators () [] . ->
() [] >
left-to-right
Unary Operators
* & ! ~ expr expr (typecast) sizeof
right-to-left
Binary Operators
* / %
+ -
>> <<
< > <= >=
== !=
& ^ |
&& ||
Ternary Operator ?:
Assignment Operators
= += -= *= /= %= >>= <<= &= ^= |=
Post increment
expr expr-- -
Comma ,

56. Good Programming Practices
Place each variable declaration on its own line with a descriptive comment
Place a comment before each logical chunk of code describing what it does
Do not place a comment on the same line as code
with the exception of variable declarations
Use spaces around all arithmetic and assignment operators
Use blank lines to enhance readability

57. Good Programming Practices
AVOID: variable names starting with an underscore
often used by the operating system and easy to miss
Place a blank line between the last variable declaration and the first executable statement of the program
Indent the body of the program
Use all uppercase for symbolic constants (used in #define preprocessor directives)
Examples:
#define PI
#define AGE 52