freestanding headers

docs/SOFTWARE.md

@@ -6,6 +6,19 @@ Honestly I have no idea. Maybe you have too much free time.
 Keep in mind that the Pepper kernel is a personal project and it's full of bugs, inconsistencies, weird ways of doing things (and I don't care because it's my toy).  
 Now if you still want to write something for this OS, thank you. Follow along.
 
+## Headers available in userspace
+
+Of course, all of the freestanding headers are available:
+- `<float.h>`: macros for floating-point types
+- `<limits.h>`: macros for integer types
+- `<iso646.h>`: macros for bitwise and logical operators
+- `<stdarg.h>`: variadic function support
+- `<stddef.h>`: definitions for `size_t`, `ptrdiff_t`, and others
+- `<stdbool.h>`: definitions for boolean types
+- `<stdint.h>`: definitions for `int_t` and `uint_t` types
+
+Also available is the `<syscall.h>` header that gives access to low-level system call interface, notably the `syscallX` function family, X being the amount of arguments to use.
+
 ## 1. Write the source code
 
 PepperOS is able to run programs written in x86 assembly, and C programs.