1. Lecture 8

2. Outline
Sizeof
Type casting
Constants
define

3. sizeof
The sizeof keyword returns the number of bytes of the given expression or type
returns an unsigned integer result
sizeof variable_Identifier;
sizeof (Data_Type);
sizeof (variable_Identifier);
Example:

4. Type Casting What is the casting?
When the type of variable and value are not the same
Example: Assigning double value to integer variable

5. Implicit casting Implicit We don’t say it But we do it
carried out by compiler automatically
char f2= ; /*cast from double to char */
int i= 98.01; /*cast from double to int */
float f = 65.6;
int i = f;
char c = i;

6. Explicit casting Explicit And we do it
We say it
And we do it
carried out by programmer using casting
int i=(int)98.1;/*cast from double to int */
char c = (char) 90;/* cast from int to char */

7. 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

8. Casting effects Casting from small types to large types
There is not any problem
No loss of data

9. Casting effects (cont’d)
Casting from large types to small types
Data loss is possible
Depends on the values

10. Casting effects (cont’d)
Casting to Boolean
If value is zero  false
If values is not zero  true
bool bool
b2 = 'a', b3 = -9,
b5 =
b4 = 4.5;
//true
//false
0, b6 = false;
b7 = '\0';

11. Constant Variables Constants
Do not want to change the value
Example: pi = 3.14
We can only initialize a constant variable
We MUST initialize the constant variables (why?!)

12. Constant
const [Data_Type] Identifier = constant_value;

13. Constant

14. Definitions Another tool to define constants
Definition is not variable
We define definition, don’t declare them
Pre-processor replaces them by their values before compiling

15. Constant
#define Identifier constant_value #define PI 3.14 #define ERROR "Disk error " #define ONE 1 #define TWO ONE + ONE

16. Example

17. Example

18. Example

19. Example

20. Examples Precedence Rules

21. int num = 0, i = 0; for (i = 0; i < 5; i++) { printf("%d", ++num);}
printf("%d", num++);
12345
01234 _ 21

22. b=(a++>0) ? printf("%d\n",a):printf("%d\n",a);
int b,a = 0;
b=(a++>0) ? printf("%d\n",a):printf("%d\n",a);
b = (a>0)?printf("%d\n",++a):printf("%d\n",a);
printf("%d\n" , a) ;
b=++a+(a>0 )?printf("%d\n",a++):printf("%d\n",a);
printf("%d\n" ,a) ; 1 _ 1 2 22

23. int a = 0; int b = 5; b = ( a++ > 0 ) ? ++a : ++b;
printf("%d %d\n" , a, b);
int a = 5;
int b = 13;
a = a * b % b / a;
b = (++a > 0 ) ? a : b++ ;
1 6
1 1 _ 23

24. int j,k,t=1,i=2; for(k=0;k<5;k++){ j = i++ + t; printf("%d",j); }
34567 _ 24

25. int a = 40, b = 30, c; c = !a <= !(c = b); printf("%d", c);
int i =1;
int j = 3*(4+i++);
printf("%d %d\n", i,j); 1
2 15 _ 25

26. int n = 5;int i = 0; while(i++ <= n) printf("%d " , i);
1 2 3 _
1 2 3 26

27. printf("%d %d %d %d", i, j, k, m); printf("%d",1 + 5&4 == 3);
int i=-3, j=2, m, k=0;
m=++i && ++j || ++k;
printf("%d %d %d %d", i, j, k, m);
printf("%d",1 + 5&4 == 3);
m=++i && ++j && k++; _ 27

28. printf("%d %d %d", i, ++i, i++); int i = 0, j = 0; j = i++ + ++i;
printf("%d %d",i,j);
3 3 1
2 2 _ 28

29. int i=1; printf("%d", i++ + ++i); int i=3; printf("%d",++i + ++i);
printf("%d\n", i); 4 10 1
C has the concept of undefined behavior, i.e. some language constructs are syntactically valid but you can't predict the behavior when the code is run. _ 29