A system call in C is a way for a program to ask the operating system for help in performing certain tasks. It allows the program to use features and services provided by the operating system.
For example, if you want to open a file and read its contents in your C program, you make system calls to the operating system. In simple English, it means you're asking the operating system to help you open the file and read its contents.
The operating system provides functions (like open and read in the example) that you can use to make these requests. You provide the necessary information, such as the file name and what you want to do with the file, and the operating system takes care of the actual work.
If something goes wrong during the process, the operating system can let you know about the error, so you can handle it appropriately.
In summary, system calls in C are a way for your program to ask the operating system to perform tasks on its behalf, like opening files, reading/writing data, managing processes, and more.