Divide and Conquer
1. Complicated programs can be divided into manageable sub programs called functions.
2. A programmer can focus on developing, debugging and testing individual functions.
3. Many programmers can work on different functions simultaneously.

toupper(): This function is used to convert the given character into its uppercase. This function will return the uppercase equivalent of the given character. If the given character itself is in upper case, the output will be the same
Syntax:
char toupper( char c);
The following statement will assign the character constant 'K' to the variable c.
char c = toupper('k');

The return statements is used to return from a function. It is categorized as a jump statement because it terminates the execution of the function and transfer the control to the called statement. A return may not may not have a value associated with it. If return has a value associated with it, that value becomes the return value for the calling statement. Even for void function return statement without parameter can be used to terminate the function.
Syntax: return expression/variable;
Example: return(a+b); return(a);
return; // to terminate the function
The functions that return no value is declared as void. The data type of a function is treated as int, if no data type is explicitly mentioned

The strupr() function is used to convert the given string into Uppercase letters.
For example:
int mair()
{
char strl[50];
cout << "\nType any string in Lower case:";
gets(str 1);
cout<< "\nConverted the Sources
string' << strl << into Uppe case 
is"<< strupr( str 1);
return 0;
}
Output:
Type any string in Lower case: computer science
Converted the Source string computer science into
Upper Case is COMPUTER SCIENCE

This function is used to check whether a given character is a digit or not. This function will return 1 if the given character is a digit, and 0 otherwise.
Syntax: int is digit(char c); When the following program is executed, the value of the variable n will be 1, since the given character is not a digit.
Example:
isdigit(3)
output :1
isdigit(A)
output: 0