1. Operating System Interface upwardly provided:
1.1 the user with: GUI + command interface (command line interface, a command interface offline)
1.2 to the application with: program interface (system calls)
System call: the operating system to the application program interface (programmer, programmers) use, it can be understood as a special function, an alternative application calling application can request to obtain the operating system kernel services through system calls.
2. The difference between system calls and library functions:
| name | the difference |
|---|---|
| General application | Direct system calls, library functions can also be used. Some library functions designed system calls, and some not involved. |
| Programming language | Provide library functions upwards. Sometimes the system call will be packaged into a library function to hide some of the details of system calls, so that programmers programming more convenient. |
| operating system | The system provides call up, so that the program can ask the kernel to the upper layer service. |
Do not involve system calls library functions: The function of taking the absolute value.
System design library function call: function such as creating a new file.
System call (classified by function):
| name | Features |
|---|---|
| Device Management | Finishing facility request, release, and so on start |
| Document Management | Complete file read, write, create, delete, etc. |
| Process Control | Complete the process of creation, cancellation, blocking, wake-up function |
| Interprocess communication | Completion message passing between processes, functions and signal transduction |
| Memory Management | Memory allocation completed, recovery and other functions |