1 / 6

COSC 456 Lesson 14

COSC 456 Lesson 14. DOS & BIOS Services. 256 different types of interrupts INT 0, INT 1, INT 2, INT 3, ........ INT 255 4 - byte address of ISR stored at 0000 : xxxx What is the type number and address of ISR? 0000:000F 42 0000:000E A5 0000:000D 04 0000:000C 00. Solution INT 3.

xander-whitaker
Download Presentation

COSC 456 Lesson 14

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. COSC 456Lesson 14

  2. DOS & BIOS Services • 256 different typesof interrupts • INT 0, INT 1, INT 2, INT 3, ........ INT 255 • 4 - byte address of ISR stored at 0000 : xxxx • What is the type number and address of ISR? 0000:000F 42 0000:000E A5 0000:000D 04 0000:000C 00

  3. Solution INT 3 • 0000:0000 through 0000:0003 for INT 0 • 0000:0004 through 0000:0007 for INT 1 • 0000:0008 through 0000:000B for INT 2 • 0000:000C through 0000:000F for INT 3 • 42A5:0400 is the address of the ISR corresponding to INT 3 • Incidentally, the total RAM space set aside for the 256 type numbers is 1KB from 0000:0000 through 0000:03FF

  4. BIOS Services • BIOS ROM has useful subroutines • DOS also provides useful services • All accessed via INT xx INT 21H AH = 02 Output character DL = character AH = 30H DOS version AL:AH (e.g. 6 .1) AH = 4C EXIT and return control to DOS.

  5. BIOS Video Service INT 10H AH = 02 cursor DH = row and DL = column BH = page (0 in graphics mode) AH = 09 Write character AL = ASCII BH = page INT 14H AH = 01 Write to port DX = com port AL = ASCII AH = 02 Read from port DX = com port AL = ASCII

  6. Smiley ( MOV DL, 1 MOV AH,2 INT 21 INT 3 Assembly language program to display a smiley face on the screen. ASCII code for smiley face is 01.

More Related