Chap 2(const var-datatype)
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This document discusses constants, variables, and data types in C programming. It defines tokens and keywords as the basic units, and explains constants and variables as values that either remain fixed or can change. Various data types are covered, including primary, user-defined, and derived types, along with modifiers that alter storage capacity. Rules for variable names and declarations are provided. The document also discusses assigning values to variables through constants, multiple assignments, and initialization.
![Token and Keyword
Token- In a C program the smallest individual units
are known as C tokens. C has six types of tokens.
1. Keyword- float, int, while
2. Identifier- main, amount
3. Constant- 10.5, 10
4. String- “ABC”, “Khulna”
5. Special symbol- [ ], { }
6. Operator- +,-,*
Keyword- Keywords are the reserve words which
have fixed meanings and that cannot be changed.
Ex- float, double, while, char, do, if, else](https://image.slidesharecdn.com/chap-2constvardatatype-150221120801-conversion-gate01/85/Chap-2-const-var-datatype-2-320.jpg)
Chap 2(const var-datatype)
- 1. Constants, Variables and Data Types Topics Token, Keyword, Identifier Constant, Variable Data types
- 2. Token and Keyword Token- In a C program the smallest individual units are known as C tokens. C has six types of tokens. 1. Keyword- float, int, while 2. Identifier- main, amount 3. Constant- 10.5, 10 4. String- “ABC”, “Khulna” 5. Special symbol- [ ], { } 6. Operator- +,-,* Keyword- Keywords are the reserve words which have fixed meanings and that cannot be changed. Ex- float, double, while, char, do, if, else
- 3. Identifier, Constant Identifier- Identifiers refer to the names of variables, functions and arrays. Constant- Constants in C refer to fixed values do not change during the execution of a program. Ex- 123, -0.75, ‘X’, “CSE” Process of declaring constant: 1. #define: #define const_name value Ex: #define MAX 100 2. const: const data_type const_name = value; Ex: const int MAX=100;
- 4. Variable Variable- A variable is a data name that may be used to store data value. A variable may take different values at different times during execution. Rules of variable name: 1. It must begin with a letter. Some systems permit underscore as the first character. 2. ANSI standard recognizes a length of 31 characters. But it should normally in between 8 char. 3. Uppercase and lowercase are different. 4. Variable name should not be a keyword. 5. White space is not allowed.
- 5. Data Types Primary data types- character, Integer, Float, Double User-defined data types- Structure, Union, Class, Enumeration Derived data types- Array, Function, Pointer, Reference
- 6. Modifier or Qualifier Modifier- The keyword like short, long, unsigned, signed can change the data storage capacity of the variable. So they are called modifier or qualifier. Type Size (bits) Range char 8 -128 to 127 int or short int 16 -32768 to 32767 unsigned int 16 0 to 65535 short int 8 -128 to 127 long int 32 -2147483648 to 2147483648 float 32 3.4E-38 to 3.4E+38 double 64 1.7E-308 to 1.7E+308 long double 80 3.4E-4932 to 3.4E+4932
- 7. Variable Declaration Declaration does two things: 1. It tells the compiler what the variable name is. 2. It specifies what type of data the variable will hold. The declaration of variables must be done before they are used in the program. Rule: Data_type Var_name; Ex: int x, y; float area;
- 8. Assigning values to Variables Rule: var_name = constant; Ex: balance = 1277.50; ch = ‘Y’; C permits multiple assignments in one line. Ex: length=10; height=5; It is also possible to assign a value to a variable at the time of variable declaration. Ex: int x = 100; C permits the initialization of more than one variables in one statement using multiple assignment operators. Ex: x = y = z = 100;