# esc¶

esc (pronounced /esk/) is an Extensible Stack-based Calculator designed for efficiency and customizability. What does this mean?

• esc is stack-based, operating using a Reverse Polish Notation (RPN)-like syntax. Rather than typing 2 + 2 and pressing an equals key, you enter the two numbers 2 and 2 onto the stack, then choose + to add them. This can be slightly awkward at first, but it means no parentheses are necessary, and for most people it becomes faster and more elegant than the standard algebraic method with a small amount of practice. In addition, it is considerably easier to customize and program.

• esc is extensible. If you frequently need to multiply two numbers together, add five, and then divide the result by pi, you can add a function to the calculator to do this specific operation using a couple of lines of Python code. The extension features are simple enough to be accessible even to people who do not know Python or have little to no programming experience.

esc operations are arbitrary Python code, so if you want to get fancy, they can get arbitrarily complicated. You can even call APIs to perform calculations or get data!

• esc is fast, simple, and terminal-based. All you need is a working terminal (at least 80×24) and your keyboard.