I am new to Linux system calls.My question is do we have a system call in Linux to plot points on screen.I googled it but could not find any simple explanation for it. I want to write a simple C program in Linux that directly plot a point on screen without the help of a C graphics library.
If there is no such system call how can I create my own system call to plot point on screen?
The lowest level hardware independent graphics interface on linux is the framebuffer. This is manipulated by writing to a device node (generally
/dev/fb0) which is the equivalent of a system call, since it is a means of sending requests to the kernel. So this does not require any libraries.
A common approach seems to be to
mmap() a chunk of user space memory representing the screen to
/dev/fb0 and then manipulating that. There are some
ioctl() calls to get information about the framebuffer display. A good starting place for information would be the docs in the kernel source --
src/Documentation/fb is a whole directory, see e.g. "framebuffer.txt" and "api.txt" there. There are a few tutorials and such around if you look online. It doesn't matter particularly which kernel version source you look at -- the last revision of "api.txt" was 2011 and "framebuffer.txt" a decade before that (so the interface is very stable).
Note that you can't use the framebuffer from within X. If you want to do graphics stuff within X, you have to use at least Xlib, or a higher level library built on that.