Google says that they treat search queries as case-insensitive and all letters in a search phrase are always interpreted in lower case. For example, searches for barack obama, Barack Obama and BARACK OBAMA will all return the same results on Google.
There are however instances when the case of a search query is as important as the search phrase itself because the word meaning can change with the case. Some examples of Capitonym words include March (month) & march (walk), Polish (language of Poland) & polish (to shine), Bill (person’s name) & bill (invoice), etc.
For instance, “Ram” is the name of a Hindu God while “RAM” is an abbreviation for Random Access Memory. They both share the same spelling and it’s the case that helps you understand the real context of the word. Unfortunately, Google searches are not case sensitive (or fold case) and hence most search results for Ram or RAM are about the “temporary” memory.
To solve this problem and help you conduct case sensitive searches on Google, someone has created a Google Appengine powered search engine at Case Sensitive Search (src) - it scans through Google search results and filters out results that match the case of your search query.