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