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diff --git a/04a/README.md b/04a/README.md new file mode 100644 index 0000000..42dbc46 --- /dev/null +++ b/04a/README.md @@ -0,0 +1,23 @@ +# stage 04a + +Rather than a compiler, this stage only consists of a simple [preprocessor](https://en.wikipedia.org/wiki/Preprocessor). +In the future, we'll run our code through this program, then run its output +through a compiler. + +It take lines like: +``` +#define THREE d3 +``` +and then replaces `THREE` anywhere in the rest of the code with `d3`. +I've provided `in04a` as a little example. +Unlike previous programs, you can control the input and output file names +without recompiling it. So to compile the example program: +``` +make out03 +./out03 in04a out04a +``` + +Although it seems simple, this program will be very useful: +it'll let us define constants and it'll work in any language. +There really isn't much else to say about this program. With that, +we can move on to [the next stage](../04b/README.md) which should be more exciting. |