StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
text
Body
copied!<p>I don't have access to tools to test right now -- in fact, what are you doing in real mode assembly on DOS anyway? -- but from memory, these should be your answers:</p> <blockquote> <p>While coding in DOS what is meant by Scroll up / Scroll down ?</p> </blockquote> <p>"Scroll up" would be "take all the stuff that's on the screen and move it upwards". The value in AL determines by how much. For example when AL=2, "Scroll up" would move all the text on the screen two lines up.</p> <p>"Scroll down" would be moving it in the other direction.</p> <p>You can move arbitrary pieces/windows of the screen by setting CX and DX appropriately. For example, since the screen presumably has 80x25 characters, when CH=1, CL=1, DH=23, DL=78, the portion that would be moved would be the entire screen except a border of one character along each edge.</p> <p>As a special case, AL=0 will cause the entire window to be cleared out.</p> <hr> <blockquote> <p>why does it says that BH is used to write blank lines at the bottom of the window ?</p> </blockquote> <p>It says that BH is the <em>attribute</em> used when writing the blank lines. In text mode, even-numbered addresses hold the characters to display, while odd-numbered addresses hold the attributes used for display. BH will give the attribute for each new character written by this call.</p> <p>The attributes are mostly foreground and background color for the character. By setting the background color and clearing the screen, you can effectively fill the screen with one color.</p> <hr> <p>I would like to clear up a point about hardware registers. You say </p> <blockquote> <p>but when i am using this code, and not defining the value of BH</p> </blockquote> <p>Please be aware that BH always has a value! You are just using the one that's lying around, by chance. Please set BH to whatever you need it to be. For example 0x07 for normal white on black colors.</p> <hr> <blockquote> <p>what is meant by a page number in a normal DOS screen ?</p> </blockquote> <p>It is similar to multiple screen buffers (front buffer, back buffer) in modern graphics programming. You can switch pages by calling <code>int 10h</code> with AH=05. See <a href="http://www.ctyme.com/intr/rb-0095.htm">Ralf Brown's Interrupt list</a>.</p>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload