add notes

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diff --git a/doc/2.md b/doc/2.md
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--- a/doc/2.md
+++ b/doc/2.md
@@ -167,3 +167,40 @@ Types of System calls:
 * information maintenance
 * communications
 * protection
+
+### Fiile Management
+
+* `create()`
+* `delete()`
+* `open()`
+* `read()`
+* `write()`
+* `reposition()`
+* `close()`
+* `get_file_attributes()`
+* `set_file_attributes()`
+* `move()`
+* `copy()`
+
+### Device Management
+
+A process may need several resources to execute
+
+* main memory
+* disk drives
+* access to files
+* `request()`
+* `release()`
+
+Sometimes I/O devices are identified by special file names, directory placement, or file attributes.
+
+### Information Maintenance
+
+* `dump()`
+* the `trace` program lists each system call as it is executed.
+
+Event microprocessors provide a CPU mode known as single step, in which a trap is executed by the CPU after every instruction.
+Many operating systems provide a time profile of a program to indicate the amount of time that the program executes at a particular location
+or set of locations.
+
+The kernel keeps information about all its processes, and system calls are used to access this information.