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6 | 6 | - Example of system calls: |
7 | 7 | - ```read()```, ```write()```, ```get_thread_area()```, ```set_tid_address()```, etc. |
8 | 8 |
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| 9 | +- A system call can be considered as a interface through which the User application code enters the Kernel mode. |
| 10 | + |
| 11 | +- System calls can be invoked from user application in 2 ways: |
| 12 | + 1. Directly calling the system call. |
| 13 | + 2. The user code calls the library function, and this function invokes or calls the systems calls when required. |
| 14 | + |
9 | 15 | ### Invoke Syscalls |
10 | | -- Usermode applications are not allow to directly execute kernel code or manipulate kernel data. |
| 16 | +- User mode applications are not allow to directly execute Kernel code or manipulate kernel data. |
| 17 | +- Linux provides a set of syscall to pass control from User mode to Kernel mode. |
11 | 18 |
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12 | 19 | ## Kernel |
13 | | -- The core of the Operation System (OS). |
| 20 | +- The core of the Operation System (OS). |
| 21 | + |
| 22 | +## Library Functions |
| 23 | +- A library is a collection of pre-compiled code. |
| 24 | +- Library functions are designed over the system calls in order to provide more additional functionality in the library functions. |
| 25 | + |
| 26 | + |
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