1 Lecture 7  Fundamental data types in C  Data type conversion:  Automatic  Casting  Character processing  getchar()  putchar()  Macros on ctype.h  Readings: Chapter 6, Section 1-12, Chapter 5

2 Fundamental data types  There are 5 basic data types in C:  char : characters  int : integers  float, double : floating values  void : empty value  char and int are collectively known as integral types  Variants of these types can be formed by adding type modifiers: long, short, signed, unsigned

3 short and long  Affect size of storage and hence range of values  Use short to conserve space  Use long to have larger range  Exact effect depends on compilers  Applicable to int: short int, int, long int  long is applicable to double too; thus the various floating point types are: float, double, long double

4 signed and unsigned  Applicable to char: char, signed char, unsigned char  Applicable to integers:  Integers are signed by default, thus signed int is the same as int  unsigned types can only store non-negative integers  Can be used with other modifiers. E.g., unsigned short int, unsigned long int

5 Fundamental data types (summary)  Long form charsigned charunsigned char signed short intsigned intsigned long int unsigned short intunsigned intunsigned long int floatdoublelong double  Short form charcharunsigned char short intlong unsigned shortunsignedunsigned long floatdoublelong double

6 The sizeof operator  Used to find the number of bytes needed to store an object (which can be a variable or a data type)  Its result is typically returned as an unsigned integer  It is called a compile-time operator because its result depends on compiler  E.g. int len1, len2; float x; len1 = sizeof(int); len2 = sizeof(x);

7 Automatic Type Conversions  Automatic type conversions are performed when:  a value is assigned to a variable of a different type  a value is passed to a function parameter of a different type  a value is returned from a function of a different type  evaluating an expression with operands of different type  When evaluating an expression, the operands are promoted to the “ highest ” type in the expression.

8 Hierarchy of Built-in Data Types  long double  double  float  unsigned long int  long int  unsigned int  int  unsigned short int  short int  unsigned char  char

9 Casts  Explicit type conversions called casts is supported in C  If x is an int, then (double) x is an expression with value x and type double. Type and value of x itself remain unchanged.  Casts can be applied to expressions, e.g, int x=4, y=3; double z; Z = (double)x/y;

10 The data type char  A character is stored as an 8-bit integer using the ASCII encoding.  Example: charc = ’a’; Internally, c is stored as the following bit pattern which is equivalent to a decimal 97  Variables of any integral type can be used to store characters. int i=’a’; printf(“%d\n”,i); /* 97 */

11 The data type char (cont’d)  Any integral expression can be printed as a character or an integer E.g.: printf(“%c\n”,95+2); /* ‘a’ */ printf(“%d\n”,95+2); /* 97 */  Depending on the compiler, the type char is equivalent to either signed char or unsigned char  signed char and unsigned char are used less often than char in typical C programs

12 The data type char (cont’d)  note that ASCII value of ‘7’ is 55 but not 7

13 Nonprinting & hard-to-print characters  Preceded by the escape character backslash \ as it is used to “escape” the usual meaning of the character that follows it, e.g., /*print “ABC” */ printf (“\”ABC\””);

14 The use of getchar () & putchar ()  Input and output of character can be done by using getchar () and putchar () which are defined in  getchar () reads a character from the keyboard. It returns the character read if successful, and EOF otherwise.  The function prototype is: int getchar(void);  putchar () writes a character to the screen. It returns the character printed if successful, and EOF otherwise.  The function prototype is: int putchar(int);

15 Example: lower- to upper-case conversion #include /* for I/O handling */ #include /* for character handling */ void main(void) { int c; while ((c = getchar()) != EOF) if (islower(c)) putchar(toupper(c)); else putchar(c); }

16 Macros and functions in  The header file ctype.h contains a set of macros and functions for character handling  The macros usually takes an argument of type int and return an int value that is either nonzero (true) or zero (false)

17 Macros and functions in (cont’d)  Note that the value of c stored in memory is not changed after the execution of the functions and macros defined in ctype.h