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2025-01-16 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Internet Technology >
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This article mainly introduces what are the differences between CAccord Cure + function library calls and system calls, which have a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let Xiaobian take you to understand.
Function library calls are part of a language or application, while system calls are part of the operating system.
System calls are made after a "trap" or interrupt discovered by the operating system kernel.
The function library calls vs. System call
Function library calls system calls are available in all ANSI C compiler versions The C function library is the same, the system call of each operating system is different, it calls a program in the function library, it calls the service of the system kernel, and the connection with the user program is an entry point of the operating system to execute in the user address space. Its running time belongs to the "user" time, and its running time belongs to the "system" time belongs to the procedure call. Less overhead requires switching to the kernel context and then switching back. There are about 300 programs in the C function library libc that have about 90 system calls in UNIx (less in MS-DOS) recorded in the third section of the UNIX OS manual.
Recorded in section II of the UNIX OS manual
Typical C function library call: system,fprintf,malloc typical system call: chidr,fork,write,brk
Library function calls are usually slower than inline expanded code because it costs the overhead of function calls. But the system call is much slower than the library function call because it needs to switch the context to kernel mode. On a SPARC workstation, timing a call to a library function is about half a microsecond. The system call takes about 70 times as long as the library function call (35 microseconds). Purely in terms of performance, you should reduce the number of system calls as much as possible. However, many programs in C function libraries perform their functions through system calls.
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