bios and dos interrupts
DESCRIPTION
Difference between BIOS and DOS its usesTRANSCRIPT
BIOS AND DOS INTERRUPTS OF INTEL 8086 MICROPROCESSORClick to edit Master subtitle styleB Y Suhas K R II Sem M.Sc Electronics Science Bangalore University7/29/12
Functional layers of a General Computers Computers can be broadlydivided into four layersApplication Program layer, is
Application Programs
a top layer of general computer, which provide us Application programs like Text Editors, Games ,GUI etc. Which is framed generally using High level languages.DOS BIOS Hardware
DOS Functions
BIOS Services
is core layer of computer ,it consist of
Hardware7/29/12
Basic Input/output System (BIOS)InIBM
PC compatiblecomputers, thebasic input/output system also known as theSystem BIOSorROMBIOS. hardware , load and start an operating system. devices such as card,keyboardandmouse,hard otherhardware. up.
The primary function of the BIOS is to set up the The BIOS is to initialize and identify system
thedisplay disk,
This process is known asbooting, or booting BIOS
software
is
stored
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on
anon-
BIOS Interrupts While using computer, we frequently need input
and output functions for reading, Displaying, accessing data in disk etc.All these functions are predefined by computer
manufacturer and made available in the system ROM with other BIOS functions. FE000H to FFFFFH.
They are stored in system ROM in locations The programmer can make use of all this
already existing large number of BIOS services for accessing I/O devices rather than writing procedures again in his programs 7/29/12
The BIOS services can be broadly classified into
the following categories Video I/O Services,
This category are used to control text and graphics on the PCs display screen.(INT 10h)System Services,
This category are used to obtain the encoded list of the standard hardware equipments connected to computer. (INT 11h)Disk I/O Services,
This are used to perform I/O operations on disk drives. (INT 13h)RS 232 Serial I/O services,
This are used to control the actions of the serial
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Keyboard I/O services,
Invokes services to receive characters and status of keyboard. (INT 15h)Printer services,
Initialize the parallel printer port, control output to a printer and read the printers status. (INT 17h)Date/Time services,
These functions are used to read or set the time maintained by BIOS. (INT 1Ah)Miscellaneous services,
Used for some special purposes7/29/12
MS-DOS was the most commonly used member
MS Disk Operating System (DOS)
of theDOS family of operating systems, and was the main operating system forIBM PC x86-basedpersonal computers.
Originally MS-DOS was designed to be an
operating system that could run on any 8086family computer. Each computer would have its own distinct hardware and its own version of MSDOS.Today, MS-DOS is rarely used for desktop
computing. Since the release ofWindows 95, it was integrated as a full product used forbootstrappingand troubleshooting, and no 7/29/12 longer released as a standalone product.
DOS Interrupts Like wise BIOS, DOS as number of routines which a
programmer can use in his programs.
It as collection of procedures to perform services such as
formatting disk, creating disk files, reading or writing files, reading from key board and writing on to display etc. BIOS .But DOS intern use large number of BIOS to provide these desired services. program using INT 21H instruction.
Working with DOS is more user friendly than working with
DOS allows the programmer to use these services in his Programs written in DOS is generally portable. But computer
system should have DOS operating system for the program Portable. Thorough knowledge of the I/O devices is not necessary while writing programs.
Execution speed is little slow compared to that of direct 7/29/12
access of hardware, or BIOS services, because DOS services
Examples of BIOS ServicesSET VIDEO MODE , INT 10H
00H
FUNCTION
Sets the video display mode Invoked with : register AH=00h register AL=mode number CODE SEGMENT START: MOV AH,00H MOV AL,00H ;00H(TEXT, 16 GRAY COLOURS,40X25)7/29/12 ;01H(TEXT ,40X25)
WRITE CHARACTER AND ITS ATTIBUTES
Obtains the ASCII code for the character at the current cursor position. Invoked with : Register AH=09H number(optional) : Register BH=Video page : Register BL=Attribute byte characters CODE SEGMENT7/29/12
: Register CX=Number of
Some examples of DOS servicesDISPLAY CHARACTER
Display character at the standard output device Invoked with : Register Ah=02H Register DL=ASCII Code Returns : Nothing
CODE SEGMENT START: MOV AH,02H ;DISPLAYS CHARACTER7/29/12
CHARACTER INPUT WITHOUT ECHO
Reads character without echoing it on the standard output of device Invoked with : Register Ah=07H Returns Code : Register AL=Character ASCII
CODE SEGMENT START: MOV AH,07H ;READS CHARACTER WITH OUT 7/29/12
GET
DATE
Obtains the month ,year ,day and day of the week as maintained by DOS Invoked with : Register Ah=2AH Returns : Register AL=day of the week (0 Sunday) : Register CX=year : Register DH=month : Register DL=day
CODE SEGMENT
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GET
TIME
Obtains the time(hh,mm,ss,ss/100) Invoked with : Register Ah=2cH Returns : Register CH=HH (0 through 23) : Register CL=MM(0 through 59) : Register DH=SS(0 through 59) : Register DL=SS/100
CODE SEGMENT TIME MOV AH,2CH ;PICKS CURRENT7/29/12
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