How could I create my own programming language?
There are many ways to create your own programming language, here is a general outline of how you can do it:
1. Choose a target platform - this will determine the amount of effort and time required to implement the language on that particular machine (e.g. if its an embedded system or web application). If your goal is to create a language for others to use then choosing something with low resource requirements such as Javascript might be better suited. 
2. Designing a language syntax is hard so you should pick a simple but powerful concept e.g. data types, operators etc.. Once you have a good idea about what kind of features you want in your language write down a basic grammar/syntax for it using a tool like Yacc/Bison or ANTLR. 
   You don't need to get fancy just try to make sure everything has sensible names. Also add some comments to explain any quirks or oddities in the language. The main purpose of these comments is not to tell people what the code does exactly but rather to give them information about why certain decisions were made and to help new programmers understand the logic behind things. 
3. Implement the core features from step 2 including the parser, tokenizer, symbol table etc... Use existing libraries or frameworks for these parts depending on what platforms you choose. You may also consider writing your own lexer, parser, pretty printer, debugger, runtime support libraries, IDE plugin or even the interpreter itself! Don't worry too much about performance right now as you still need to validate that the compiler works correctly before optimizing anything.  It's best to start small by implementing just enough to demonstrate working compilation. Keep refactoring until you reach full compilability. For example if your target platform supports C++ then you might consider implementing templates, lambdas, RAII and const correctness all at once which would take quite a while without having much point to it other than making sure it works correctly.