1. Fundamental Data Types

2. Declaration All variables must be declared before being used.
Tells compiler to set aside an appropriate amount of space in memory to hold a value.
Enables the compiler to perform operations using the declared variables.

3. Basic Data Types char character int integer float floating-point
double double floating-point
void valueless

4. Modifying the Basic Types
Type modifier:
signed unsigned long short
When a type modifier is used by itself, then int is assumed.
Modifier Same As
signed signed int
unsigned unsigned int
long long int
short short int

5. Data Type char
Have Seen: Chars are treated as small integers & conversely small ints are treated as chars.
char c = ‘a’;
printf (“%c”, c + 1) b
printf (“%d”, c + 2) 99
Each char variable stored in 1 Byte 8 Bits: a 1 1 1

6. String of binary digits are called bit strings.
A bit string is interpreted as a binary number bnbn-1……b2b1b0 a
This bit string has the value:
1 25 + 120= 97

7. 3 types:
1) char 2) unsigned char 3) signed char
Each uses 1 Byte.
Signed char to 127
Unsigned char to 255

8. Data Type int
INTEGERS : Include the natural counting numbers and their negatives.
INTEGRAL DATA TYPES:
int short long unsigned

9. word size(bits) of the machine is machine dependent
The magnitude of the number that an int variable can hold depends on ___________?
2 Byte word ~ K To K
-215, …, -3, -2, -1, 0, 1, 2, 3, …, 215-1
4 Byte word ~ -2 Billion To +2 Billion
-231, …. -3, -2, -1, 0, 1, 2, 3, …, 231-1
word size(bits) of the machine is machine dependent

10. Integer overflow: Value too large for defined Storage Location.
Typically program continues to run but incorrect results.
The programmer must strive at all times to avoid integer overflow.

11. Types short, long, unsigned
short - used where conserving storage is a concern (usually 2 Bytes).
-32 Thousand To Thousand
-215, , …, -3, -2, -1, 0, 1, 2, 3, …, 215-1
long - needed for larger integers (usually 4
bytes).
-2 Billion To +2 Billion
-231, , …, -3, -2, -1, 0, 1, 2, 3, …, 231-1

12. Unsigned - no sign bit, same number bytes as int.
The range, u, of values:
0  u  2wordsize-1
2 Byte word ~ 0 To + 64 Thousand
0, 1, 2, 3, …, 216-1
4 Byte word ~ 0 To + 4 Billion
0, 1, 2, 3, …, 232-1

13. Suffix:
u - 20u
l – 20l
ul - 20ul
(case not significant)
IF no suffix with constant - system will choose the first of : int - long - unsigned long
That can hold the value.

14. The Floating Types float double long double Suffixes for constants
f or F float F
l or L long double L
Any unsuffixed floating constant is of type double (working type).

15. Notation: exponential or decimal
Must have Exponent or Dec pt or Both. e e
0e0 correct 0.0
.e0 wrong
May not contain any blanks or special characters.
Typical Storage: Float < Double

16. Float: 4 Bytes - about 6 decimal places of accuracy- single precision.
Precision: The number of significant decimal
digits that floating value carries.
Range: Limits of largest & smallest possible
values that can be in a variable of that
type.
Float: Bytes - about 6 decimal places of
accuracy- single precision.
Double: 8 Bytes - about 15 decimal places
of accuracy- double precision.

17. Internal Representation
FLOAT:
SEEEEEEEE mmmmm…m
DOUBLE:
SEEEEEEEEEEE mmmmmmm…m
Implied mantissa of 1 is not stored.
Sign bit (1 for neg-otherwise pos).

18. Float:
Precision: significant digits.
Range: to 10+38
0.d1d2d3d4d5d6  10n
Double:
Precision: 15 significant digits (252  1015)
Range: to
 103

19. Note:
1. Not all Real numbers are exactly
representable in binary memory.
2. Floating Arithmetic ops, unlike integer
arithmetic, may not be exact.

20. Compile-Time Operator sizeof
Unary operator used to find the number of Bytes needed to store an object.
sizeof(object)
Object
Data type int , float, …
Expression a + b
Array
Will cover
later
Structure

21. Assuming that integers are 4 bytes and doubles are 8 bytes.
double f;
printf("%d ",sizeof (f));
printf(''%d", sizeof(int)); 4

22. sizeof(char) = 1
sizeof(short)  sizeof(int)  sizeof(long)
sizeof(signed)=sizeof(unsigned)=sizeof(int)
sizeof(float)
<= sizeof(double )
<= sizeof( long double)

23. Conversions
When constants and variables of different types are mixed in an expression, the compiler converts all operands to the type of the largest operand- Called Type Promotion.
First, all char and short values are automatically elevated to int. Called integral promotion.
int + int = int
short short = int
Arithmetic Conversion (See pg. 217)

24. char ch;
int i;
float f;
double d,result;
result= (ch / i) + (f * d) – (f + i);
int double float
double

25. Casts Casts - Explicit conversions. (type) expression If i is int:
(float) i will change expression value to
float, i is not changed.
(float) i/2

26. Apply to an Expression:
(float) (‘c’ + 3)
Cannot apply to an Assignment:
(int) f = 3: illegal
As an unary operator, a cast has the same precedence as any other unary operator.
(float) i + 3 ( (float) i ) + 3

27. /* print i and i/2 with fractions */
int main(void)  {   int i;  
for(i=l; i<=100; ++i)      printf(''%d //2 is: %f \n", i, (float) i /2);
return 0; }

28. General forms:
(int) char expression- ordinal value of char expression
(char) int expression- character with the ordinal value of int expression
(int) float expression- truncates the float expression
(float) int expression- converts int to float
(double) float exp- converts float to double