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README.md

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+I didn't figure out how to get started on this topic alone, this is all
+following the great information provided by Nora Sandler on the topic of writing
+a C compiler, I'd highly recommend checking out her [blog
+series](https://norasandler.com/2017/11/29/Write-a-Compiler.html) and
+[book](https://nostarch.com/writing-c-compiler)!
+
+# How to run
+
+For a C source code file `prog.c`, this can be compiled by running `cargo run
+prog.c`:
+```
+> cat prog.c
+int main() {
+   return 2;
+}
+> cargo run prog.c
+> cat prog.s
+    .globl main
+main:
+    pushq %rbp
+    movq %rsp, %rbp
+    subq $0, %rsp
+    movl $2, %eax
+    movq %rbp, %rsp
+    popq %rbp
+    ret
+```
+
+The output file stem (filename without extension) will be the same as the input
+file. Ie, `test.c` would be compiled to `test.s`.
+
+# What is supported
+
+## Target architecture
+
+This is only targeting x86-64.
+
+## C language features
+
+Currently, this only supports compiling C programs that use a *very* limited
+subset of the C programing language features:
+- a single (main) function
+- a single return statement
+- the return statement can contain nested applications of unary operators, but
+the innermost operand must be a numerical literal