Scrolling Text in Asm

[matias_beretta]

Hello, thanks for reading my topic...

I want to scroll everything one line up so i've to

move the memory 160-4000 to 0

160 (START OF THE SECOND LINE)

4000 = 25 * 80 * 2 (EVERYTHING!)

IS THIS CORRECT?

Well, I'm sorry about my bad english, I'm from Argentina...

[frank]

Everything looks fine to me, one more thing though you should clear the last line by setting it too spaces when you are done with the move operation.

[matias_beretta]

thanks...

[mohammed]

hope this code help you it's from bran's kernel
http://osdever.net/bkerndev/index.php

Code: Select all

/* These define our textpointer, our background and foreground
*  colors (attributes), and x and y cursor coordinates */
unsigned short *textmemptr;
int attrib = 0x0F;
int csr_x = 0, csr_y = 0;

/* Scrolls the screen */
void scroll(void)
{
    unsigned blank, temp;

    /* A blank is defined as a space... we need to give it
    *  backcolor too */
    blank = 0x20 | (attrib << 8);

    /* Row 25 is the end, this means we need to scroll up */
    if(csr_y >= 25)
    {
        /* Move the current text chunk that makes up the screen
        *  back in the buffer by a line */
        temp = csr_y - 25 + 1;
        memcpy (textmemptr, textmemptr + temp * 80, (25 - temp) * 80 * 2);

        /* Finally, we set the chunk of memory that occupies
        *  the last line of text to our 'blank' character */
        memsetw (textmemptr + (25 - temp) * 80, blank, 80);
        csr_y = 25 - 1;
    }
}

definition of functions that used

Code: Select all

void *memcpy(void *dest, const void *src, size_t count)
{
    const char *sp = (const char *)src;
    char *dp = (char *)dest;
    for(; count != 0; count--) *dp++ = *sp++;
    return dest;
}

void *memset(void *dest, char val, size_t count)
{
    char *temp = (char *)dest;
    for( ; count != 0; count--) *temp++ = val;
    return dest;
}

unsigned short *memsetw(unsigned short *dest, unsigned short val, size_t count)
{
    unsigned short *temp = (unsigned short *)dest;
    for( ; count != 0; count--) *temp++ = val;
    return dest;
}

i know that you asked about asm but understanding the main idea may be helpful