Print and Clear in C without libraries [closed] - c

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I'm trying to develop a Operative System.
It works, but the function "print" that I've written has an error:
If I print two Strings only one will be displayed, and the command \n does not work.
My questions are:
How to use the command \n?
and
How to create the function clear without using libraries?
This is the function print:
void print(char* message, int color)
{
char* mem = (char*)(0xb8000);
while(*message != 0)
{
*mem = *message;
mem++;
message++;
*mem = (char*)color;
mem++;
}
}
PS It Works, but the problem is that if I use the function print two times (with or whitout \n it prints me only the second part.

Answer 1

To simulate a line break you probably need to write as many spaces to the video memory as there are characters left in the current line. Hence, you need to remember how many characters you wrote to the current line.
The same applies for scrolling. You need to copy the memory in a way that the last line on the screen becomes blank again.

Answer 2

You should have some context of the printing function.
eg: you should have a global(or static) variable to remember your last printed position of the video output memory.
something like:
```
static int last_pos = 0;
void print(char* message, int color)
{
char* mem = (char*)(0xb8000);
mem += last_pos * 2;
while(*message != 0)
{
if(*message == '\n') {
set the mem to next line and calculate the new last_pos
continue;
}
*mem = *message;
mem++;
message++;
*mem = (char*)color;
mem++;
last_pos ++;
if (last_pos >= max_video_buffer) {
move content the buffer to scroll the screen
or
simply reset the last_pos and mem to restart from top-left.
}
}
}
```
when do clearing: just fill the whole video output memory to empty and reset the last_pos