What is Macro? Why do we use the macro?

• Data types in C language are defined as the data storage format that a variable can store a data to perform a specific operation.
• Data types are used to define a variable before to use in a program.
• Size of variable, constant and array are determined by data types.

• Integer data type allows a variable to store numeric values. The storage size of int data type is 2 or 4 or 8 byte. It varies depend upon the processor in the CPU.
• Character data type allows a variable to store only one character. Storage size of character data type is 1.
• Float data type allows a variable to store decimal values. Storage size of float data type is 4. This also varies depend upon the processor in the CP.
• Double data type is also same as float data type which allows up-to 10 digits after decimal.

sizeof() function is used to find the memory space allocated for each data type in C.

• The amount of memory space to be allocated for a variable is derived by modifiers.
• Modifiers are prefixed with basic data types to modify (either increase or decrease) the amount of storage space allocated to a variable.
• For example, storage space for int data type is 4 byte for 32 bit processor. We can increase the range by using long int which is 8 byte. We can decrease the range by using short int which is 2 byte.

• There are 5 modifiers available in C language. They are,

  • short
  • long
  • signed
  • unsigned
  • long long

• Enumeration is a data type that consists of named integer constants as a list.
• It start with 0 (zero) by default and value is incremented by 1 for the sequential identifiers in the list.

• Void is an empty data type that has no value.
• We use void data type in functions when we don’t want to return any value to the calling function.
• Example:

void sum (int a, int b); – This function won’t return any value to the calling function.
int sum (int a, int b); – This function will return value to the calling function.

• We use void data type in pointer like “void *p”. It means, pointer “p” is neither pointing to int data type nor char data type. It acts as generic pointer. We are using void pointer when we are not sure on the data type that this pointer will point to. We can use void pointer to refer either integer data or char data. But, this void pointer should not be dereferenced without explicit type casting.
• We use void in functions as “int function_name (void)”. Here void means, this function does not pass any argument.

• C tokens are the basic buildings blocks in C language which are constructed together to write a C program.
• Each and every smallest individual unit in a C program are known as C tokens.

• C tokens are of six types. They are,

  1. Keywords               (eg: int, while),
  2. Identifiers               (eg: main, total),
  3. Constants              (eg: 10, 20),
  4. Strings                    (eg: “total”, “hello”),
  5. Special symbols    (eg: (), {}),
  6. Operators              (eg: +, /,-,*)

• Each program elements in a C program are given a name called identifiers.
• Names given to identify Variables, functions and arrays are examples for identifiers.
• Example: x is a name given to integer variable in above program