System Calls and Parameter Passing, Summaries of Operating Systems

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SYSTEM CALLS

d Programming interface to the services provided by the OS d Typically written in a high-level language (C or C++) d Mostly accessed by programs via a high-level rather than direct system call use d Three most common APIs are Win 32 API for Windows, POSIX API for POSIX-based systems (including virtually all versions of UNIX, Linux, and Mac OS X), and Java API for the Java virtual machine (JVM)

SYSTEM CALL IMPLEMENTATION

U Typically, a number associated with each system call

. maintains a table indexed

according to these numbers

U The system call interface invokes the intended

system call in OS kernel and returns status of the

system call and any return values

API – SYSTEM CALL – OS RELATIONSHIP

SYSTEM CALL PARAMETER PASSING

U Often, more information is required than simply identity of

desired system call

. Exact type and amount of information vary according to

OS and call

U Three general methods used to pass parameters to the OS

. Simplest: pass the parameters in registers

. Parameters stored in a block , or table, in memory, and

address of block passed as a parameter in a register

. Parameters placed, or , onto the by

the program and off the stack by the

operating

system

PARAMETER PASSING VIA TABLE

TYPES OF SYSTEM CALLS

U File management

. create file, delete file

. open, close file

. read, write, reposition

. get and set file attributes

U Device management

. request device, release device

. read, write, reposition

. get device attributes, set device attributes

. logically attach or detach devices

TYPES OF SYSTEM CALLS (CONT.)

U Information maintenance

. get time or date, set time or date . get system data, set system data . (^) get and set process, file, or device attributes U Communications . create, delete communication connection . send, receive messages if to or U From to . create and gain access to memory regions . transfer status information . attach and detach remote devices

EXAMPLES OF WINDOWS AND UNIX SYSTEM CALLS

STANDARD C LIBRARY EXAMPLE

d C program invoking printf() library call, which calls write() system call