1 files changed, 44 insertions, 0 deletions
diff --git a/docs/std/io.md b/docs/std/io.md
new file mode 100644
index 0000000..825728d
--- /dev/null
+++ b/docs/std/io.md
@@ -0,0 +1,44 @@
+# Standard Library: IO (`std/io.zc`)
+
+The `std/io` module provides standard input/output functionality, including printing to stdout and reading from stdin.
+
+## Usage
+
+```zc
+import "std/io.zc"
+
+fn main() {
+    // Printing
+    io.println("Hello %s", "World");
+    
+    // Formatting strings
+    autofree var s = io.format_new("Value: %d", 42);
+    
+    // Reading input
+    io.print("Enter name: ");
+    autofree var name = io.readln();
+}
+```
+
+## Functions
+
+### Output
+
+| Function | Signature | Description |
+| :--- | :--- | :--- |
+| **print** | `print(fmt: char*, ...) -> int` | Prints formatted output to stdout. |
+| **println** | `println(fmt: char*, ...) -> int` | Prints formatted output to stdout with a newline. |
+
+### Formatting
+
+| Function | Signature | Description |
+| :--- | :--- | :--- |
+| **format** | `format(fmt: char*, ...) -> char*` | Formats string into a static buffer (returns pointer). **Not thread-safe**. |
+| **format_into** | `format_into(buf: char*, size: usize, fmt: char*, ...) -> int` | Formats string into a user-provided buffer. |
+| **format_new** | `format_new(fmt: char*, ...) -> char*` | Formats string into a newly allocated buffer (caller must free). |
+
+### Input
+
+| Function | Signature | Description |
+| :--- | :--- | :--- |
+| **readln** | `readln() -> char*` | Reads a line from stdin. Returns heap-allocated string (caller must free) or `NULL` on EOF/error. |