This document is a tutorial on C programming language concepts including unions, bitwise operators, bit-fields, and enumerations. It contains code examples and explanations of each concept over 19 pages. Key points covered include how unions allow variables of different types to share the same memory space, how bitwise operators manipulate bits, how bit-fields optimize memory usage, and how enums create integer constants represented by identifiers. The document encourages solving quizzes and contacting the author for any questions.

1. C Programming
Language
By:
Yogendra Pal
yogendra@learnbywatch.com
Dedicated to My mother and Father

2. t
y
Keep your notebook with you.
Write important point and questions that comes in your mind
Solve Mind band exercise.
C
Rewind when not clear
Ask Questions by call or SMS or by mail
Keep Watching Keep Learning
THIS IS UNIONS, BITWISE,
BIT-FIELDS AND ENUM
2

3. Unions
• A variable that may hold variables of different
types and sizes.
• Only contains one data member at a time.
• Member of union share same space.
• Last data member defined can be accessed.
3

4. Unions
• Unions declaration
union u_tag {
int ival;
float fval;
char cval;
}u;
– Use union keyword to declare a union.
– u_tag is the name of union.
– ival, fval & cval are the member of the u_tag
union.
4

5. Union…
• All operation applied on structures can be
applied on unions.
• Access:
– Union_name.member;
– Union_pointer -> member;
• Unions may occur within structures and arrays,
and vice versa.
5

6. Bitwise-operators
• All data represent as sequence of bits.
• A bit can be zero or one.
• C provides some operators to work on bits.
6

7. Bitwise-operators
• & (Bitwise AND)
– Set 1 if both operands are 1.
A B A &B 011 3
0 0 0 & 101 5
0 1 0 001 1
1 0 0
1 1 1
7

8. Bitwise-operators
• I (Bitwise OR)
– Set 1 if any one operand is 1.
A B A|B 011 3
0 0 0 | 101 5
0 1 1 111 7
1 0 1
1 1 1
8

9. Bitwise-operators
• ^ (Bitwise Exclusive-OR)
– Set 1 if exactly one operand is 1.
A B A^B 011 3
0 0 0 ^ 101 5
0 1 1 110 6
1 0 1
1 1 0
9

10. Bitwise-operators
• << (left-Shift)
– Shifts the bits of the first operand left by the
number of bits specified by the second operand; fill
from the right with 0 bits.
5 0 0 1 0 1
– 5 << 1
0 1 0 1 0 10
10

11. Bitwise-operators
• >> (Right-Shift)
– Shifts the bits of the first operand right by the
number of bits specified by the second operand.
5 0 0 1 0 1
– 5 >> 1
0 0 0 1 0 2
11

12. Bitwise-operators
• ~ (One’s Complement)
– All 0 bits are set to 1 and all 1 bits are set to 0.
A ~A
0 1
1 0
12

13. Bitwise-Assignment operator
• &= (Bitwise AND assignment operator)
• |= (Bitwise OR assignment operator)
• ^= (Bitwise Exclusive OR assignment operator)
• <<= (Left-shift assignment operator)
• >>= (Right-shift assignment operator)
13

14. Operator Associativity Type
() [] . -> left to right Highest
+ - ++ -- ! & * ~ sizeof (type) right to left Unary
* / % left to right multiplicative
+ - left to right additive
<< >> left to right shifting
< <= > >= left to right relational
== != left to right equality
& left to right bitwise AND
^ left to right bitwise OR
| left to right bitwise OR
&& left to right logical AND
|| left to right logical OR
?: right to left conditional
= += -= *= /= &= |= ^= <<= >>= %= right to left assignment
, left to right comma
14

15. Bit-fields
• Member variable of a structure with the
specified bits size.
struct dob{
unsigned int dd : 5;
unsigned int mm : 4;
};
• Better memory utilization.
• int / unsigned;
15

16. Unnamed bit-field
• Used as the padding.
struct rent{
unsigned int x : 5;
unsigned int : 4;
unsigned int y : 4;
};
16

17. Enumeration
• Integer constants represented by identifiers.
enum days { sun, mon, tue, wed, thu, fri, sat }
• It creates a new data type (days).
• Values start at 0 and increment by 1.
• If you want to set the start value write as:-
enum days { sun = 1, mon, tue, wed, thu, fri, sat }
17

18. Enumeration…
• To use inside program declare variable like:-
enum days day;
• OR, use typedef
enum days Day;
Day day;
18

19. To get complete benefit of this tutorial solve all the quiz on
www.learnbywatch.com
For any problem in this tutorial mail me at
yogendra@learnbywatch.com
with the subject “C”
For Other information mail at
info@learnbywatch.com
Keep Watching Keep Learning
NEXT IS FILE I/O
19