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INTRODUCTION

Here is the VGA (Video Graphics Array) driver, it's a driver that allows you to display text on the screen. In the project, it's stored it the src/utils/VGA folder and can be used with the VGA.h include.

TABLE OF CONTENTS

How it works ?

The VGA is provided by the BIOS, so we have to follow some rules, the first things to know is that the VGA is a buffer of 80 x 25 characters starting from the adress 0xB8000, each characters is 2 bytes long, the first one is the character (ASCII) and the second one is the color of the character. A color is a 4 bits values (0-15) and the first 4 bits are the background color and the last 4 bits are the foreground color. The color is defined in the vga.h file.

How to use it ?

The VGA folder provides an API that can be included to use all the functions. Only the VGA.h file is needed to use the VGA driver. It's made this way to have a cleaner code

Functions list

vga_clear_screen

This function clear fill all the screen with the character ' ' and the color 0x00. Here is the prototype of the function:

void vga_clear_screen();

vga_putchar_at

This function display a character at the given position with the given color. It's the basic function to display a character on the screen. It will return 1 if the character is displayed and will return a negative value in case of error. Errors:

  • -1: The position is out of the screen (x > 80 or y > 25) Here is the prototype of the function:
int vga_putchar_at(char c, uint8_t color, uint8_t x, uint8_t y);

vga_putstr_at

This function display a string at the given position with the given color. It's a basic function that display a string on the screen. It will return the string length if the string is displayed and will return a negative value in case of error. Errors:

  • -1: The position is out of the screen (x > 80 or y > 25) Here is the prototype of the function:
int vga_putstr_at(const char *str, uint8_t color, uint8_t x, uint8_t y);

vga_print_int_at

This function display an integer at the given position with the given color. It's a basic function that display an integer on the screen. It will return the string length if the integer is displayed and will return a negative value in case of error. Errors:

  • -1: The position is out of the screen (x > 80 or y > 25) Here is the prototype of the function:
int vga_print_int_at(int num, uint8_t color, uint8_t x, uint8_t y);

vga_printf_at

This function display a formatted string at the given position with the given color. It's a basic function that display a formatted string on the screen. It will return the string length if the string is displayed and will return a negative value in case of error. Errors:

  • -1: The position is out of the screen (x > 80 or y > 25) Here is the prototype of the function:
int vga_printf_at(const char *format, uint8_t color, uint8_t x, uint8_t y, ...);

Want to contribute ?

If you want to add a function in the VGA driver, you can do it by creating a new file in the src/utils/VGA folder and add the function in the VGA.h file. Pay attention to add the documentation of the function in this folder. And please make clean commented code with a proof of working code.