Question

Code needs to be written by KickC - Optimizing C-compiler for 6502

you must write a simple function that displays a text message on the screen.

The function signature should be: void print_to_screen(char *message);

This function should accept a string, and write each character of the string to the screen, and increase the current_screen_x variable for each character printed.

You will need to maintain a pointer to the current line on the screen, as well as the position on that line.

You could do this with definitions like: unsigned char *current_screen_line = $0400; unsigned char current_screen_x = 0; Implement the print_to_screen() function.

Now create a second function called print_newline() that advances current_screen_line to the next line, and resets current_screen_x to zero, so that printing can continue from the next line.

Call your new print_to_screen() and print_newline() functions from your reset() function to print the two messages “YOURFAN operating system starting...” and “testing hardware” on separate lines.

Answer 1

/*
Author - Ripul Vohra
You can run this code in any C compiler and check the output..
*/
#include <stdio.h>
unsigned int current_screen_line=0; //globally declared so that every function can use it
unsigned int current_screen_x=0; //globally declared so that every function can use it

//This function will print the given string char by char and keep pointer to last char printed.
void print_to_screen(char *message)
{
  
//Running the for loop to access each character and print it to screen and side by side increasing
//the current_screen_x variable.Finding length of screen using strlen() in built function.
  
for(int i=0;i<strlen(message);i++)
{
printf("%c",message[i]); //printing each character
current_screen_x=(current_screen_x+1); //increasing current_screen_x for a particular line

}
  
}

//inserting a new line so that next char will be printed from next line and incrementing the line pointer
//(current_screen_line) by 1 and for newline,setting current_screen_x=0;
void print_newline()
{
print_to_screen("\n"); //going to next line on screen
current_screen_line=(current_screen_line+1); //incrementing the line pointer
current_screen_x=0; //pointer to last character in current line
}

//Reset function will print the given two lines in question
//Just pass the first string to print_to_screen and add a new line using print_newline
//Pass the second string to print_to_screen to print on screen
void reset()
{
print_to_screen("YOURFAN operating system starting...");
print_newline();
print_to_screen("testing hardware");
}

int main()
{
reset();
//You can check poistion of cursor anytime using this print statement -
//printf("\nCursor is at Line %d and Word %d",current_screen_line,current_screen_x);
//Note - Lines and words are 0 indexed here,which means 1ST Line & Word will be labelled as 0th Line & 0th word.
}

OUTPUT-