Understanding Constants, Variables, and Data Types in C Programming for Deaf Education

1. Data Structure and c K.S.Prabhu Lecturer All Deaf Educational Technology

2. C Tokens

3. C Tokens

6. Keywords • It has 32 keywords.

7. #include<stdio.h> #include<conio.h> void main() { char yn; clrscr(); do { puts("enter y/n(yes/no)"); yn=getchar(); fflush(stdin); if(yn!='y'&&yn!='n') puts("invalid input"); } while(yn!='y'&&yn!='n'); getch();

8. Constants • A constant is an entity that doesn't change during the execution of a program. • Followings are the different types of constants. • Real constant • Integer Constant • Character Constant • String Constant

9. 1. Real Constant : • It must have at least one digit. • It must have a decimal point which may be positive or negative. • Use of blank space and comma is not allowed between real constants. • Example: • +194.143, -416.41

10. Real Constant • It must have at least one digit. • It must have a decimal point which may be positive or negative. • Use of blank space and comma is not allowed between real constants. • Example:+194.143, -416.41

11. Integer Constant • It must have at least one digit. • It should not contain a decimal place. • It can be positive or negative. • Use of blank space and comma is not allowed between real constants. • Example: • 1990, 194, -394

12. Character Constant • It is a single alphabet or a digit or a special symbol enclosed in a single quote. • Maximum length of a character constant is 1. • Example:'T', '9', '$'

13. String Constant • It is collection of characters enclosed in double quotes. • It may contain letters, digits, special characters and blank space. • Example:“I love Deaf“ “ All Deaf Educational Technology”

14. Identifier • An identifier is used for any variable, function, data definition, etc. • In the C programming language, an identifier is a combination of alphanumeric characters. • An underline and the remaining being any letter of the alphabet, any numeric digit, or the underline.

16. String • Strings in C are represented by arrays of characters. • The end of the string is marked with a special character, the null character, which is simply the character with the value 0. • The null character has no relation except in name to the null pointer. char string[15] = "Hello world!";

17. Sample code Program #include<stdio.h> #include<conio.h> void main() { char in_str[21]; clrscr(); puts("Enter a string to a maximum of 20 characters"); getch(); } output Enter a string to a maximum of 20 characters Youth

18. Variables • It is date name used date value called by valuables. • It is a data name which is used to store data and may change during program execution. • It is opposite to constant.

19. Variable name is a name given to memory cells location of a computer where data is stored. Syntax: {data types}{Variables name}=[value]

20. Sample code Program Example: Int count index; Float area price; Chal class types; Example of main program:- Main { Int a,b,c,=10; Char x; Float num;

21. Types of variables

22. Local variables • These variables only exist inside the specific function that creates them. • They are unknown to other functions and to the main program. • As such, they are normally implemented using a stack.

23. Example: • { • Int a, b, c, =10; local variable • Char x; • Float num; • }

24. Global variables • These variables can be accessed by any function comprising the program. • They are implemented by associating memory locations with variable names.

25. Example: • {Int a, b, c, =[10,20,30] ; Global variable • Chal x; • Float • } (or) • {Int a = [10] • Int b = [20] • Int c = [30] • Chal [15] • Float • }

26. Example of Global Variable Example: { Int a, b, c, =[10,20,30] ; Char x; Float num; } { Int a = [10]; Int b = [20]; Int c = [30]; Char[15]; Float num; }

27. TYPEDEF STATEMENT • typedef is a keyword in the C and C++ programming languages. • The purpose of typedef is to assign alternative names to existing types. • types declared with typedef end with ( '_t' ) • (e.g., size_t, time_t) Syntax;- • Typedef exp1, exp2,….., expn

28. All data types in between typedef and identifier can now be referred to by the identifier alone The statement. typedef structtnode *Treeptr; typedef structtnode { int count; structtnode *left; structtnode *right; } Treenode;

29. Example of Typedeaf

30. Enumerated DataTypes • The data type enum allows used identifier as value • Syntax: • Enum identifier {Element} Element 1, Element 2…..to Element n;

31. Example of main program • Enum days {sun, mon, tue, wed, thu, fir, sat} • Enum color{red, blue, orange, pink, green,} • Enum holiday{Sunday, Saturday} • Enum rainbow {red, blue, orange, yellow, green,}