Skip to main content

Changing the case (lower, upper) of Strings

In this article, we will be designing two functions to change the case of strings. One would change a string from lower case to upper case while the other would do the opposite.

Although we have pre-defined functions for doing this in a header file, but this article is for those who dare to know how all these operations are done internally.

Changing the case: How is it done?

The main theory lies in the way C++ treats character constants and strings. Have a look at the following code:

  #include<iostream.h>

  void main(void)
  {
   char first='A';
   char second=65;

   cout<<first;
   cout<<endl;

   cout<<second;
   cout<<endl;
  }

whose output is:

   A
   A
   Press any key to continue

This is because ‘A’ and its ASCII code 65 are equivalent to the compiler and in c++ we can manipulate it in whatever way we like.

Now look at the following code:

  #include<iostream.h>

  void main(void)
  {
   char arr[4]="ABC";
   char arr2[4]={65,66,67};

   cout<<arr;
   cout<<endl;

   cout<<arr2;
   cout<<endl;
  }

Whose output is (yeah you guessed it right!):

   ABC
   ABC
   Press any key to continue

So this proves that strings can also be expressed (manipulated) by ASCII codes.

ASCII code of some characters:

   A: 65    a: 97
   B: 66    b: 98
   C: 67    c: 99
   …        …
   …        …

From the above, we can conclude that by increasing or decreasing the ASCII codes of a character by 32, we can change its case. Just as shown in the following code:

  #include<iostream.h>

  void main(void)
  {
   char chr='A';
   char chr2='b';

   cout<<chr;
   cout<<endl;

   chr=chr + 32;
   cout<<chr;
   cout<<endl<<endl;

   cout<<chr2;
   cout<<endl;

   chr2=chr2 - 32;
   cout<<chr2;
   cout<<endl;
  }

OUTPUT:

   A
   a

   b
   B
   Press any key to continue

This theory can also be applied to strings.

Now, that you know the main theory behind we can jump straight to the example program to illustrate all this:

Keep reading the comments though!

  // C++ example program to show
  // how case(uppercase and lowercase)
  // of strings can be changed from
  // one to the other
  #include<iostream.h>

  void to_upper(char *);
  void to_lower(char *);

  void main(void)
  {
   char str[50]="I Love C++. The number 1 language!";

   to_upper(str);
   cout<<str;

   to_lower(str);
   cout<<endl;
   cout<<str;

   cout<<endl;
  }

  // takes a character array
  // as argument and changes
  // it to upper case
  // NOTE: special symbols and
  // numbers remains the same
  void to_upper(char *str)
  {
   // while end of the string
   // has not been reached
   while(*str!='\0')
   {
    // change only if its a
    // lower case character
    // intelligent enough not to
    // temper with special
    // symbols and numbers
    if(*str>=97 && *str<=122)
      *str-=32;

    str++;
   }
  }

  // takes a character array
  // as argument and changes
  // it to lower case
  // NOTE: special symbols and
  // numbers remains the same
  void to_lower(char *str)
  {
   while(*str!='\0')
   {
    // change only if its a
    // UPPER case character
    // intelligent enough not to
    // temper with special
    // symbols and numbers
    if(*str>=65 && *str<=90)
      *str+=32;

    str++;
   }
  }

Good-Bye!

Popular posts from this blog

Fix For Toshiba Satellite "RTC Battery is Low" Error (with Pictures)

RTC Battery is Low Error on a Toshiba Satellite laptop "RTC Battery is Low..." An error message flashing while you try to boot your laptop is enough to panic many people. But worry not! "RTC Battery" stands for Real-Time Clock battery which almost all laptops and PCs have on their motherboard to power the clock and sometimes to also keep the CMOS settings from getting erased while the system is switched off.  It is not uncommon for these batteries to last for years before requiring a replacement as the clock consumes very less power. And contrary to what some people tell you - they are not rechargeable or getting charged while your computer or laptop is running. In this article, we'll learn everything about RTC batteries and how to fix the error on your Toshiba Satellite laptop. What is an RTC Battery? RTC or CMOS batteries are small coin-shaped lithium batteries with a 3-volts output. Most laptops use

The Best Way(s) to Comment out PHP/HTML Code

PHP supports various styles of comments. Please check the following example: <?php // Single line comment code (); # Single line Comment code2 (); /* Multi Line comment code(); The code inside doesn't run */ // /* This doesn NOT start a multi-line comment block /* Multi line comment block The following line still ends the multi-line comment block //*/ The " # " comment style, though, is rarely used. Do note, in the example, that anything (even a multi-block comment /* ) after a " // " or " # " is a comment, and /* */ around any single-line comment overrides it. This information will come in handy when we learn about some neat tricks next. Comment out PHP Code Blocks Check the following code <?php //* Toggle line if ( 1 ) {      // } else {      // } //*/ //* Toggle line if ( 2 ) {      // } else {      // } //*/ Now see how easy it is to toggle a part of PHP code by just removing or adding a single " / " from th

Introduction to Operator Overloading in C++

a1 = a2 + a3; The above operation is valid, as you know if a1, a2 and a3 are instances of in-built Data Types . But what if those are, say objects of a Class ; is the operation valid? Yes, it is, if you overload the ‘+’ Operator in the class, to which a1, a2 and a3 belong. Operator overloading is used to give special meaning to the commonly used operators (such as +, -, * etc.) with respect to a class. By overloading operators, we can control or define how an operator should operate on data with respect to a class. Operators are overloaded in C++ by creating operator functions either as a member or a s a Friend Function of a class. Since creating member operator functions are easier, we’ll be using that method in this article. As I said operator functions are declared using the following general form: ret-type operator#(arg-list); and then defining it as a normal member function. Here, ret-type is commonly the name of the class itself as the ope