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README.md

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-# symphony_stdlib
+# Symphony Stdlib
+
+This is a standard library for symphony.
+It is both intended as a practical toolkit to develop more complex software as well as a teaching resource.
+
+If you just want to use the standard library [stdlib.asm] is your main header, include it after your code.
+You'll also need to include globals.asm in the first line of your main assembly file.
+
+If you are using it as a learning resource have a look at the [teaching folder](teaching).
+
+If you are intersted in contributing have a look at [CONTRIBUTING.md]
+
+---
+
+## ABI
+
+### Calling Convention
+n.a. zr
+preserved: sp, r8 - r12
+scratch: flags, r1 - r7
+arguments: r1 - r7 (r1 = 1st argument, r6 = 6th arg/stack args, r7 = 7th arg/stack res)
+result: r1, r2 (r1 = low word, r2 = high word)
+return address: r13
+
+### Stack
+grows downwards from top of memory
+arguments are passed in reverse order with the stack so:
+lowest address = 1st stack arg
+highest address = last stack arg
+
+### Types
+
+#### String
+Strings are stored in memory as null terminated sequences of bytes encoding ascii characters.
+They should be passed by reference.
 
-standard library for symphony