LectureBitMSDOSProgramming.pptVIP

Lecture 19 16-Bit MS-DOS Programming Assembly Language for Intel-Based Computers, 4th edition Kip R. Irvine Chapter Overview MS-DOS and the IBM-PC MS-DOS Function Calls (INT 21h) Standard MS-DOS File I/O Services MS-DOS and the IBM-PC Real-Address Mode MS-DOS Memory Organization MS-DOS Memory Map Redirecting Input-Output Software Interrupts INT Instruction Interrupt Vectoring Process Common Interrupts Real-Address Mode Real-address mode (16-bit mode) programs have the following characteristics: Max 1 megabyte addressable RAM Single tasking No memory boundary protection Offsets are 16 bits IBM PC-DOS: first Real-address OS for IBM-PC Derived by Microsoft from Gary Kildalls Digital Research CP/M Later renamed to MS-DOS, owned by Microsoft MS-DOS Memory Organization Interrupt Vector Table BIOS DOS data Software BIOS MS-DOS kernel Resident command processor Transient programs Video graphics text Reserved (device controllers) ROM BIOS MS-DOS Memory Map Redirecting Input-Output (1 of 2) Input-output devices and files are interchangeable Three primary types of I/O: Standard input (console, keyboard) Standard output (console, display) Standard error (console, display) Symbols borrowed from Unix: symbol: get input from symbol: send output to | symbol: pipe output from one process to another Predefined device names: CON, PRN/LPT1, LPT2, LPT3, NUL, COM1, COM2 Redirecting Input-Output (2 of 2) Standard input, standard output can both be redirected Standard error cannot be redirected Suppose we have created a program named myprog.exe that reads from standard input and writes to standard output. Following are MS-DOS commands that demonstrate various types of redirection: INT Instruction The INT instruction executes a software interrupt. The code that handles the interrupt is called an interrupt handler. Syntax: Interrupt Vectoring Process Common Interrupts INT 10h Video Services INT 16h Keyboard Services INT 17h Printer Services INT 1Ah Time of Day INT 1Ch User Timer Int